Sciencemadness Discussion Board

nitroglycerin

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z13123 - 20-9-2014 at 21:40

Thanks for the reply. I made sure it was neutral by testing it with pH paper. I'll try to detonate it ASAP and be more prepared next time. For some reason, detonating it slipped my mind because I was too focused on synthesizing it... I'll make sure I have a better way to detonate it next time.

Hennig Brand - 10-10-2014 at 05:41

That stump from a few posts ago, which was not removed, was blasted recently with a 400g charge of nitroglycerine powder containing 10% NG. The blast was successful and the two pieces of the stump still in the ground are each attached by a single large root and can be wiggled by hand easily. A set of come alongs will be able to pull them out by anchoring to a nearby tree. A higher velocity dynamite or a larger charge would have removed the stump completely. I have found that once they are blown apart like this, however, that the remaining pieces are very easy to pull out of the ground.

You can see in the last picture the aluminum casing from the failed urea nitrate charge. It was actually a fairly difficult stump to blast because of the very large roots which were very spread out and well anchored and with large holes between them for the explosive gases to escape through.

400g Charge.jpg - 228kB Charged and Tamped.jpg - 537kB Just After Blast.jpg - 546kB Post Blast 1.jpg - 273kB Post Blast 2.jpg - 278kB


[Edited on 10-10-2014 by Hennig Brand]

Hawkguy - 12-10-2014 at 15:16

As to the idea of making small Nitroglycerin charges, I've found that most commonly people soak NG into Ammonium Nitrate or similar. Is it possible to soak NG into a TNT mixture?

roXefeller - 12-10-2014 at 17:25

I don't see any reason it wouldn't work, a more brisant version of TNT, though I wouldn't hold it for a while. I imagine the mixed phase will end up separating, liquid from solid. That is already a common problem with dynamite though, but more so with TNT. A fine sized TNT would help with this but its waxy nature would make it slow at best to form a fine powder.

Bert - 12-10-2014 at 20:30

Quote: Originally posted by Hawkguy  
As to the idea of making small Nitroglycerin charges, I've found that most commonly people soak NG into Ammonium Nitrate or similar. Is it possible to soak NG into a TNT mixture?


You could certainly DO that- But it would not seem to make economic sense, nor to provide any advantage. Quite the reverse, it could well lead to a lower stability and greater sensitivity than TNT has.

See the following for commercial practices and economic/engineering considerations related to nitroglycerin mixtures-

Tenney Davis: Chemistry of Powder & Explosives

Phokion Naoum: Nitroglycerin and Nitroglycerin Explosives

It was once common to use a mixture of various nitrotoluene byproducts of 2,4,6 TNT manufacture ("TNT oils") mixed into nitroglycerin to lower the freezing point of dynamites- Pure TNT was not used, AFAIK. Making use of waste stream from another explosive manufacturing process to manufacture low freezing dynamite, rather than spending additional money and time to make nitro glycol or nitro sugars as low freezing additions made economic sense to manufacturers at the time.

hyfalcon - 13-10-2014 at 03:27

HB, I hope the windows to the house in the background held up. I can understand the reluctance to use anything larger then you did. That's mighty close the the dwelling to be using HE.

Hennig Brand - 13-10-2014 at 08:00

Was just a little thump actually, nothing that would disturb even a close neighbor. The earth and stump absorb most of the energy/noise; unless of course an excessively large charge is used, then it can be noisy. If that charge had been initiated above ground then there would have been one hell of bang. Most people are surprised just how quiet a properly charged shot can actually be. Yes, I was being a bit extra careful though, because of the proximity to buildings, etc.

Hennig Brand - 27-10-2014 at 05:43

The stump pieces were in fact easily removed. A four wheel drive Toyota Tacoma was used to pull out the two remaining large pieces of the stump. Roots are similar to guy-wires; when there is only one guy-wire the wood is no longer well anchored to the ground and can be easily removed. Also the blast tends to heave the pieces at least a bit, removing tension from the guy-wires/roots, which also weakens the roots hold on the ground facilitating removal.

Stump Piece Removed 1.jpg - 307kB Stump Piece Removed 2.jpg - 300kB Stump Piece Removed 3.jpg - 292kB


[Edited on 27-10-2014 by Hennig Brand]

synthesis large quantity nitroglycerin

ecos - 9-1-2015 at 09:20

Hi All,

I synthesized small amounts of NG (~5 gm) for several times using AN salt instead of nitric acid.

I am just asking if someone could synthesize large amounts of NG ? and what precautions he took into consideration?.

I know that NG is sensitive and dangerous but I am sure there are skillful guys here who could share their experience.

Bert - 9-1-2015 at 10:22

There are many descriptions here of doing such things- Start by reading this whole thread, perhaps?

ecos - 9-1-2015 at 10:31

Hi Bert :)

I already went through many posts here , maybe i dropped the correct ones.

I am really talking about large quantities :) , something over 1 Liter.

Bert - 9-1-2015 at 11:53

You want advice and pro tips on how to make over 1 l of nitroglycerin as a single batch.



:o




I am going to have to formulate a proper response to that, as regards your safety and forum policy- that may take me a while. I do not type accurately with tachycardia.

ecos - 9-1-2015 at 12:51

I am just asking for sake of knowledge, i read some patents about machine that can do so but i wonder if it can be made in a lab or so.

I could make 200 mL of NG in my small lab but I never needed such amount.

so dont think i am crazy but it is very interesting to know if someone could manage that process before.

Hennig Brand - 9-1-2015 at 13:29

Of course it can be done, and relatively safely too, by people who are experienced. It was routinely made in ton quantities in batch processes industrially from what I understand. The risk factor increases sharply with increasing batch size, however, and even the pros did have occasional accidents. There is no way for someone experienced to write you a simple procedure that is going to account for every possible eventuality or give you the situational awareness that they would have. I would advise that you stick with smaller batches and just make more of them if you need more NG. I think the most I ever made was 250mL in a single batch. Cleared up any deficits in attention that I had, at least while performing the synthesis. :D

Is making large batches really worth it to you? If it is, start small and develop a good working understanding of the process and the dangers involved first.

The processes involved are relatively simple, but there are very real hazards.

Bert - 9-1-2015 at 13:43

Sometimes the way a question is asked shows the questioner has not yet done enough research.

Take a look at my post on this same page, see the links to two books in sciencemadness.org library.

Naoum' book details industrial equipment and reagents used for every scale- From bench procedure suited to students/material testing lab, pilot plants and full scale factory layouts for 1,000's of kg. Along with historical development of such procedures and mention of not a few deadly accidents.

Tenney Davis gives lab bench scale synthesis and describes commercial production and handling, including continuous process machinery.

I warn you: Batch size in such reactions can not be scaled linearly with safety. If you try your 5ml process at 200 X size, you will likely experience a runaway, and may well be injured or killed.

When scaled up:

Volume (and heat production!) goes up as a cube.

The surface area (area needed for heat to escape!!!) goes up as the square.

It is very possible to set yourself up with a batch size and reagent addition profile where no amount of external cooling will save you.

Note that even the smallest glycerin testing batch sized apparatus detailed in Naoum has circulating chilled water cooling? It is not there for swank.





image.jpg - 314kB


[Edited on 9-1-2015 by Bert]

Nitroglycerine in Large Batches

Hennig Brand - 11-1-2015 at 09:30

It is very possible that I have made errors in the following calculations. If you see some, please let me know.

Here is a correction to calculated amount of ice:

Quote: Originally posted by Hennig Brand  
Just realized I messed up the calculation for the amount of ice needed on the last page of this thread. The amount of ice required was based on the mass of glycerine nitrated, assuming complete nitration, and I calculated as if it was based on the amount of NG.

Quote: Originally posted by Hennig Brand  


An ice water bath is an excellent way to cool a nitroglycerine nitration reaction mixture.

Water heat of fusion: 334J/g (334kJ/kg)

Mass of ice needed for cooling per gram of glycerine nitrated assuming no heat transfer to surroundings:

(1.43kJ/1g Glycerine) * (1kg Ice / 334 kJ) = 0.0043 kg Ice/1g Glycerine Nitrated (4.3g Ice/g glycerine nitrated)

Ice needed for synthesis of 1L of NG = 1000mL(1.6g/mL)(4.3g Ice/g glycerine) = 6880g of Ice (6.88kg of Ice)
This is assuming no heat transfer from the surroundings! In reality the amount of ice required could be much more.



Here is the correction:

An ice water bath is an excellent way to cool a nitroglycerine nitration reaction mixture.

Water heat of fusion: 334J/g (334kJ/kg)

Mass of ice needed for cooling per gram of glycerine nitrated assuming no heat transfer to surroundings:

(1.43kJ/1g Glycerine) * (1kg Ice / 334 kJ) = 0.0043 kg Ice/1g Glycerine Nitrated (4.3g Ice/g glycerine nitrated)

Ice needed for synthesis of 1L of NG = 1000mL(1.6g/mL) / (227.09 g/mol) * (92.09382 g/mol) * (4.3g Ice/g glycerine) = 2790g of Ice (2.79kg of Ice)
This is assuming no heat transfer from the surroundings! In reality the amount of ice required could be much more.

What a difference a little slip can make!


As Bert was saying volume increases much more quickly than the outside surface area of the vessel. A sphere is considered as an idealized representation of a round bottom reaction flask, full of nitration mixture. In reality it would only be partially full and would have an open top and very likely a flat bottom in most cases, but the following is just an approximation.

Volume of Sphere = 4/3 * pi * r^3
Surface Area of Sphere = 4 * pi * r^2

If the radius, or diameter, is doubled the volume of the spherical vessel increases by eight time (2^3 = 8), while the outer surface area only increases by four times (2^2 = 4). If we increase the diameter by three times, we get 27 times the volume and only 9 times the outer surface area. Since heat produced is directly proportional to the volume of the reaction mixture and in most amateur settings reaction cooling takes place through the side walls of the reaction vessel, it is very important to make sure that adequate cooling is provided for.

I worked through the numbers a bit this morning, because I became interested myself.

The heat evolved in a nitration reaction includes not only the heat of nitration but also the heat of dilution. If the nitration reaction temperature is allowed to rise too high, oxidation processes can start to take place which are very exothermic and can quickly lead to uncontrollable runaway reactions. If this starts to happen the nitration mixture must be immediately drowned in cold water to stop the reaction. In small scale NG nitrations, runaway reactions are normally fairly benign, but as the surface area to volume ratio of the reaction mixture gets smaller (larger batch) a runaway reaction can be very dangerous often resulting in explosion if the reaction mixture is not promptly drowned in water.


Heat of Nitration
"According to information from different sources the heat of nitration of glycerol to trinitroglycerine varies from 120 to 170 kcal (ca. 502 to 711 kJ) per 1 kg of glycerine." (Urbanski Vol. 2 pg. 46) The higher value of 711 kJ / 1 kg of glycerine will be assumed, for the heat of nitration, as a worst case type of scenario.


Assume starting with pure glycerine, 95% HNO3 and 95% H2SO4. Assume the following composition for the mixed acid:

HNO3....40%
H2SO4...55%
H2O.......5%

Assume 6.5 parts by mass nitration mixture per part of glycerine will be used.

Per 1g Glycerine:

Pre Nitration Numbers:

HNO3: 0.4(6.5g) = 2.60g
H2SO4: 0.55(6.5g) = 3.58g
H2O: 0.05(6.5g) = 0.33g
Total mass = 6.51g

Percent by weight of total acid: 95%
Percent HNO3 based on anhydrous acid: 42%
Enthalpy of mixed acid solution estimated from attached graph: -86kJ/kg


Post Nitration Numbers:

Per 1mole of glycerine nitrated, 3 moles of HNO3 are consumed and 3 moles of water are produced.

HNO3: 2.60g - 2.053g = 0.547g
H2SO4: 3.58g
H2O: 0.33g + 0.5864g = 0.916
Total mass = 5.04g

Percent by weight of total acid: 82%
Percent HNO3 based on anhydrous acid: 13%
Enthalpy of mixed acid solution estimated from attached graph: -254kJ/kg

Heat of Dilution
Heat of dilution = [5.04g / 1000g/kg * (-254kJ/kg)] - [6.51 / 1000g/kg * (-86kJ/kg)]
Heat of Dilution = -0.72kJ/1g Glycerine Nitrated

Total Heat Produced
Total Heat Produced = Heat of Nitration + Heat of Dilution of Mixed Acid
Total Heat Produced = -0.711kJ/1g Glycerine + -0.72kJ/1g Glycerine
Total Heat Produced = -1.43KJ/1g Glycerine

The nitration of glycerine is an extremely fast reaction, typically about 80% of the glycerine can be nitrated in less than one second according to Urbanski Vol. 2. The associated section, discussing this, from Urbanki was snipped and made into a pdf which is attached. Assuming vigilant temperature monitoring and good agitation/mixing, all that need be done to accurately control the temperature is to very carefully control the addition rate (assuming the ambient temperature isn't a lot above room temperature). Good cooling makes the process much safer and certainly much faster, however, since the reaction does produce a lot of heat which needs to be removed. As the batch size gets larger it quickly becomes impractical and dangerous to not have powerful cooling in place.

Heat Capacity of the Reaction Mixture
The ability of the reaction mixture to absorb heat was examined.

From Engineeringtoolbox.com:

Specific Heats:

Sulfuric Acid: 1.38kJ/kg.K
Nitric Acid: 1.72 kJ/kg.K
Water: 4.19kJ/kg.K

Nitroglycerine: 1.7814kJ/kg.K (A Dictionary of Applied Chemistry)

The post reaction mixture was used in the calculation. Interactions between species were neglected, so as to provide a simple approximation of the heat capacity of the mixture.

Average Heat Capacity of post reaction mixture = 0.547g/7.5089g(1.72kJ/kg.K) + 3.58g/7.5089g(1.38kJ/kg.K) + 0.916/7.5089g(4.19kJ/kg.K) + 2.4659g/7.5089g(1.7814kJ/kg.K)
Heat Capacity of post reaction mixture = 1.860996kJ/kg.K

Assuming no heat dissipation, for -1.43kJ heat produced per 1g glycerine:

deltH = m * Cp * deltT

Temperature Rise Assuming No Heat Dissipation = deltaT
deltaT = 1.43 kJ / [(1.860996kJ/kg.K) * (7.5089g/1000g/kg)]
deltaT = ca. 102K (102C)

Without adequate heat removal, the temperature of the reaction mixture could easily climb to very dangerous levels and this gets more complicated/difficult as the reaction mixture gets larger.

An ice water bath is an excellent way to cool a nitroglycerine nitration reaction mixture.

Water heat of fusion: 334J/g (334kJ/kg)

Mass of ice needed for cooling per gram of glycerine nitrated assuming no heat transfer to surroundings:

(1.43kJ/1g Glycerine) * (1kg Ice / 334 kJ) = 0.0043 kg Ice/1g Glycerine Nitrated (4.3g Ice/g glycerine nitrated)

Ice needed for synthesis of 1L of NG = 1000mL(1.6g/mL)(4.3g Ice/g glycerine) = 6880g of Ice (6.88kg of Ice)
This is assuming no heat transfer from the surroundings! In reality the amount of ice required could be much more.


Very close temperature monitoring, glycerine addition control, excellent mixing and excellent cooling are all very important.

Good agitation/mixing keeps the temperature differential on either side of the vessel side wall at near maximum resulting in a near maximum rate of heat transfer/rate of cooling. Good agitation also prevents localised hot spots which can/will result in exothermic decomposition (oxidation processes) which could easily result in uncontrollable temperature rise/runaway.

Remember to get lots of ice before proceeding with the nitration, especially if it is a larger scale batch size.

Remember to keep the temperature below 30C. Actually, keeping the temperature well below 20C is safer and according to Urbanski these lower temperatures normally produce higher yields as an added bonus for staying farther away from the dangerous, higher temperature, region.



Attachment: Nitroglycerine Nitration Reaction Rate from Urbanski Vol. 2.pdf (184kB)
This file has been downloaded 509 times

Attachment: Heat Effects Due To Dilution During Aromatic Nitrations By Mixed Acid In Batch Conditions.pdf (324kB)
This file has been downloaded 437 times

Enthalpy-Concentration Diagram for HNO3-H2SO4-H2O Mixtures.jpg - 248kB


[Edited on 12-1-2015 by Hennig Brand]

[Edited on 14-2-2015 by Bert]

Bert - 11-1-2015 at 11:48

Anything over 100g glycerin input, you probably want a metal reaction vessel for better conduction. Naoum a page or two earlier describes a sheet Lead vessel in an ice water bath for the same procedure shown with the fancy glassware above.

Moving upwards in batch size, you start seeing diagrams of cooling coils with circulating chilled water/brine and mixing paddles INSIDE the reaction vessels... And jolly little tech notes about related issues: If the cooling coil starts leaking water into the concentrated nitrating acids, the heat of dilution can easily lead to a runaway...

[Edited on 11-1-2015 by Bert]

Hennig Brand - 11-1-2015 at 12:48

I think it might be playing with fire a little bit, so to speak, but as long as the addition rate was carefully controlled, and the temperature was closely monitored, I don't see any problems other than the process taking longer than if all the high powered cooling equipment were installed. With good agitation glycerine doesn't hang around in the nitration mixture and then all react at once like sometimes happens with other nitrations. Glycerine nitrates very quickly and completely even at very low temperatures. The reactions are very exothermic, however, and the temperature must be watched like a hawk and additions must be slow and controlled. A big bucket of cold water must be handy to drown the reaction if controlling the temperature becomes impossible (which should only happen if the process was rushed and/or there was a lack of cooling for the size of the reaction).

Obviously the bigger one goes the more dangerous it becomes, especially if there is a lack of understanding about the process.

That glass apparatus above is very neat, but I don't think it is necessary for 200g or so of NG. It would probably be very convenient though. I have made about a cup (~250mL) of NG before in a glass coffee pot. Other than my nerves it all went fine. It took a good couple of hours to add all the glycerine, though, and I was stirring with a glass rod by hand (I now only swirl for safety). It wouldn't be very hard to rig up a Teflon paddle driven by a cordless drill (powered by a mains fed power supply). With a good ice bath or salt ice bath and the Teflon paddle working vigorously cooling should be fantastic through a thin walled glass round bottomed vessel.


Thermal Conduction Through Glass

I think you have a point about the different materials and thermal conductivity, but I don't think it is as much of an issue as you think at these small scales.


Thermal Conductivities

Borosilicate Glass: 1.14w/m.K (camglassblowing.co.uk)
Stainless Steel: 16w/m.K (Engineeringtoolbox)
Lead: 35 w/m.K (" ")
Carbon Steel: 43w/m.K (" ")
Cast Iron: 55w/m.K (" ")

So yes, glass really stinks in the thermal conductivity department. However, I still don't think it is much of a problem at the scales we are discussing.

From the reaction numbers in the last post, a 1L reaction mixture can accommodate the nitration of about 247g of glycerine. The spherical vessel will be assumed to be twice as large as needed and only using half its surface area for cooling to the ice bath.

Q/t = [K * A * (TH - TC)] / d
Heat conduction/time = [Thermal conductivity * Area * (Temperature hot side - Temperature cold side)] / Thickness of sidewall

Assume that a 15C temperature differential is maintained. Just measured a coffee pot and it was 2mm thick or less; will use 2mm wall thickness.

Q/t = [1.14w/m.K * 0.03838m^2 * (25C - 10C)] / (0.002m)
Q/t = 328watts or 328J/s

Total Heat Produced = 247g Glycerine * (1.43kJ/1g Glycerine) = 353kJ

Time needed to transfer all heat using a 15C temperature differential = 353kJ / (0.328kJ/s) = 1077s or 17.9minutes

As long as the temperature differential was maintained at least 15C from one side of the glass sidewall to the other, 247g of glycerine could be nitrated, producing about 500g of NG, and the heat produced could be transferred in less than 18 minutes.

I can see how this is maybe starting to push the limits, however, a much greater temperature differential could be maintained which would increase the rate of heat transfer.

One of the important points to take note of; if a vessel with low conductivity, such as one made of glass, is used the ability to deal with a temperature/energy surge is less.


[Edited on 12-1-2015 by Hennig Brand]

ecos - 12-1-2015 at 02:27

Hi Bert and Hennig,

This is a photo for the reaction vessel for NG at Nobel's first company.



for me it looks horrible :) , I took the picture from BBC documentary video, here is a link for this part : http://youtu.be/01pjt_K-94M?t=33m16s

It scare me when you talk about metal vessel for the reaction because we use conc Nitric or Sulfuric acid.

I always try to keep the reaction temperature between 0 to 5 degrees to be on the safe side.

I always use 5 times the amount of NG for synthesis as a rule of thumb.

it is really interesting to know how large scale production of NG works.

[Edited on 12-1-2015 by ecos]

[Edited on 12-1-2015 by ecos]

Hennig Brand - 12-1-2015 at 07:35

Ecos,

Please resize that image. It is way too big and it is messing up this page. I normally go 800 width, but I think you can go wider than that now and still be fine. If you don't have a program to resize pictures you could try GIMP. It is what I have been using and it is free to download.

Nice picture, notice how the guy is sitting on a one legged stool. One way to help ensure the guy watching the thermometer stays alert.

ecos - 12-1-2015 at 07:44

Hi Hennig,

I modified the picture, it should be better now for your screen/

your last statement was mentioned in the youtube link i provided above , i wonder how a man can sleep while he is synthesizing NG :D , he would loose his life for sure.
what interest me is the size of the reaction vessel and the valves !!

I wonder how would he control the situation if the temperature starts to increase gradually without stopping , he would need a bigger container full of ice or even KOH to stop the run out !

safety precautions is a point of interest here.

Hennig Brand - 12-1-2015 at 08:55

Thanks. People often do become complacent or comfortable, after days or weeks, even when doing something as serious and important as monitoring the temperature of a large scale batch NG production process. The flow of glycerine could be slowed or stopped completely depending on the temperature of the reaction mixture. If things really became uncontrollable, there was a large reservoir of water below the reactor which the entire contents of the reactor could be quickly dumped into by pulling a lever or some other control. From what I have read this was a common set-up to deal with runaway reactions. Everything was normally designed to limit the damage in case of explosion as well. The buildings and the grounds around them were normally designed to direct a blast up and limit the extent of the damage.

I have seen that documentary before, it is very good. I think I will watch it again. That image you posted was actually put up for discussion in one of the classes I took at university a few years back.

ecos - 13-1-2015 at 05:47

Regarding the gelignite , do anybody have an instruction video for this?. I know the process but it would be more efficient to see a video.

i only found this video but it has no instructions : http://youtu.be/lcgSDrpWawQ

Hennig Brand - 13-1-2015 at 06:32

The following snip-it was taken from, "Lectures on Explosives" Third Edition (1902) by Willoughby Walke. There are other types of Gelignite as well such as ammon gelignite.



Gelignite Composition from Lectures on Explosives.jpg - 83kB

I don't think I have seen a video, but I haven't really looked for one either. Basically the gelatine and dope are prepared separately and then the two are well mixed. The gelatine can be much easier formed by using a bit of acetone, I have found, and then later allowing the acetone to evaporate. The dope is well dried and powdered before mixing with the gelatine. It is a very simple process for the most part.

Apparently ammon gelignites replaced regular gelignite for the most part.


[Edited on 13-1-2015 by Hennig Brand]

ecos - 13-1-2015 at 06:38

nice to know about this mixture, I always use this mixture:
90% NG
9% NC
1% Sodium bicarbonate as anti-acid, (Naoum used chalk in his book but i use sodium bicarbonate , not sure if i do the correct thing )

i hope if there is a video for the process :)

Hennig Brand - 13-1-2015 at 06:52

I think that mixture is normally referred to as blasting gelatine, though I see on the internet the terms gelignite and blasting gelatine often seem to be used interchangeably. Gelignite is a high gelatine content dynamite with an absorbent dope of powdered nitrate and fuel from what I understand.

Hennig Brand - 24-1-2015 at 05:12

Quote: Originally posted by Hennig Brand  
I think it might be playing with fire a little bit, so to speak, but as long as the addition rate was carefully controlled, and the temperature was closely monitored, I don't see any problems other than the process taking longer than if all the high powered cooling equipment were installed. With good agitation glycerine doesn't hang around in the nitration mixture and then all react at once like sometimes happens with other nitrations. Glycerine nitrates very quickly and completely even at very low temperatures. The reactions are very exothermic, however, and the temperature must be watched like a hawk and additions must be slow and controlled. A big bucket of cold water must be handy to drown the reaction if controlling the temperature becomes impossible (which should only happen if the process was rushed and/or there was a lack of cooling for the size of the reaction).

Obviously the bigger one goes the more dangerous it becomes, especially if there is a lack of understanding about the process.

That glass apparatus above is very neat, but I don't think it is necessary for 200g or so of NG. It would probably be very convenient though. I have made about a cup (~250mL) of NG before in a glass coffee pot. Other than my nerves it all went fine. It took a good couple of hours to add all the glycerine, though, and I was stirring with a glass rod by hand (I now only swirl for safety). It wouldn't be very hard to rig up a Teflon paddle driven by a cordless drill (powered by a mains fed power supply). With a good ice bath or salt ice bath and the Teflon paddle working vigorously cooling should be fantastic through a thin walled glass round bottomed vessel.


Thermal Conduction Through Glass

I think you have a point about the different materials and thermal conductivity, but I don't think it is as much of an issue as you think at these small scales.


Thermal Conductivities

Borosilicate Glass: 1.14w/m.K (camglassblowing.co.uk)
Stainless Steel: 16w/m.K (Engineeringtoolbox)
Lead: 35 w/m.K (" ")
Carbon Steel: 43w/m.K (" ")
Cast Iron: 55w/m.K (" ")

So yes, glass really stinks in the thermal conductivity department. However, I still don't think it is much of a problem at the scales we are discussing.

From the reaction numbers in the last post, a 1L reaction mixture can accommodate the nitration of about 247g of glycerine. The spherical vessel will be assumed to be twice as large as needed and only using half its surface area for cooling to the ice bath.

Q/t = [K * A * (TH - TC)] / d
Heat conduction/time = [Thermal conductivity * Area * (Temperature hot side - Temperature cold side)] / Thickness of sidewall

Assume that a 15C temperature differential is maintained. Just measured a coffee pot and it was 2mm thick or less; will use 2mm wall thickness.

Q/t = [1.14w/m.K * 0.03838m^2 * (25C - 10C)] / (0.002m)
Q/t = 328watts or 328J/s

Total Heat Produced = 247g Glycerine * (1.43kJ/1g Glycerine) = 353kJ

Time needed to transfer all heat using a 15C temperature differential = 353kJ / (0.328kJ/s) = 1077s or 17.9minutes

As long as the temperature differential was maintained at least 15C from one side of the glass sidewall to the other, 247g of glycerine could be nitrated, producing about 500g of NG, and the heat produced could be transferred in less than 18 minutes.

I can see how this is maybe starting to push the limits, however, a much greater temperature differential could be maintained which would increase the rate of heat transfer.

One of the important points to take note of; if a vessel with low conductivity, such as one made of glass, is used the ability to deal with a temperature/energy surge is less.


[Edited on 12-1-2015 by Hennig Brand]


I used the wrong heat transfer equation above which does change the result by a small amount. The equation used was for a flat wall and what I should have used was the equation for a sphere.

Q/t = (T1 - T2) / Rsph

where:

Rsph = (r2 - r1) / (4 * pi *r1 * r2 * k)

Rsph is the conductive resistance of the spherical layer

Using a 1L reaction mixture in a 2L spherical flask:

V = 4/3 * pi * r1^3
r1 = 0.0782 m

wall thickness = 2mm

r2 = 0.0802m

Rsph = (0.0802m - 0.0782m) / (4 * pi * 0.0802m * 0.0782m * 1.14w/m.K)
Rsph = 0.02226 C/w

Q/t = (25C - 10C) / (0.02226C/w)
Q/t = 673.8w

For half of surface area used:

Q/t = 673.8w/2 = 337w or 0.337 kJ/s

Time needed to transfer all heat using a 15C temperature differential = 353kJ / (0.337kJ/s) = 1047s or 17.5minutes

This actually improves the situation by a little bit.


In case anyone was interested here are the equations for one dimensional, steady state, heat conduction for a cylindrical layer as well:

Q/t = (T1 - T2) / Rcyl
Rcyl = ln(r2 - r1) / (2 * pi * k * L)

[Edited on 24-1-2015 by Hennig Brand]

Hennig Brand - 25-1-2015 at 14:59

Quote: Originally posted by Hennig Brand  


In case anyone was interested here are the equations for one dimensional, steady state, heat conduction for a cylindrical layer as well:

Q/t = (T1 - T2) / Rcyl
Rcyl = ln(r2 - r1) / (2 * pi * k * L)



That last equation should read:

Rcyl = ln(r2/r1) / (2 * pi * k * L)

Man I need to get my shit together.

ecos - 26-1-2015 at 06:43

Interesting equations for real
I am really sorry if my question would look simple : is it possible to provide an example for 1 L so we can know how to use these equations ?

Bert - 26-1-2015 at 13:42

Quote: Originally posted by Hennig Brand  
I think that mixture is normally referred to as blasting gelatine, though I see on the internet the terms gelignite and blasting gelatine often seem to be used interchangeably. Gelignite is a high gelatine content dynamite with an absorbent dope of powdered nitrate and fuel from what I understand.


Blasting gelatine is usually just NG, enough NC to gell and bring OB to neutral and usually a small amount of antacid such as calcium carbonate. It's high velocity, good for hard rock blasting, can cut steel & do similar jobs- But it tends to lose sensitivity to initiation over time.

Gelignites are active base dynamites where the NG has been pre gelatinized with a small amount of NC before mixing into the dope, whatever mixture of powdered oxidizer(s)/fuel(s)/antacid are being used. They don't lose sensitivity in storage in my experience-

Amonium nitrate based gelignite is a nice versatile explosive, works fine in a range from 10% to 60%+ NG, depending on how fast you need it to shoot.

Hennig Brand - 26-1-2015 at 13:52

No problem, r1 (inside radius) above was found by using 0.002m^3 (2L) for volume in the reaction flask/sphere volume equation. Outside radius was found by adding wall thickness (0.002m (2mm) in the example) to the inside radius. It was assumed that the flask would be half full (1L reaction mixture). Once the rate of heat transfer was found for the 2L flask/sphere it was divided by 2 to get the rate of heat transfer for the 1L reaction mixture. In reality there could be some heating or cooling at the surface of the liquid reaction mixture, inside the flask, but what was done should still be a close approximation of steady state heat transfer with a continuous 15C temperature differential. So the above was an example for a 1L reaction mixture. 

Bert, that was more or less my understanding of blasting gelatin and gelignite as well.


[Edited on 27-1-2015 by Hennig Brand]

Volume & Area Equations for Partially Filled Spherical Vessels

Hennig Brand - 28-1-2015 at 12:28

Notice how above I calculated the rate of heat transfer for a full 2L flask and then simply divided by two for the assumed 1L contents. This is a special case, since 1L would be half full and because of symmetry the surface area is also halved. Normally the spherical vessel used would not be exactly half full, however, and the relationship between volume and area is not as simple.

Here are a couple of equations which could be useful to someone trying to perform heat transfer calculations based on a partially filled spherical vessel/flask.

V = 1/3 * pi * H^2 * (3 * R - H)

A = 2 * pi * R * H

where:
V = Volume of contents in partially filled spherical vessel
A = Inside Surface Area of curved surface, next to contents, of partially filled spherical vessel
H = Height of contents in partially filled spherical vessel
R = Inner Radius of spherical vessel

Equations for other shapes can be found too, in texts or online.


[Edited on 28-1-2015 by Hennig Brand]

ecos - 6-2-2015 at 03:20

Hi Hennig,

I always go through your equations and got lost easily :) , As I understand you try to calculate the heat transfer or heat generation due adding NG with acids into ice ! , your first equations says we need ice with volume at least 6 times the volume of mixture (NG + acids)

I didnt see any equations showing the required temp of ice+water!.
if someone used water with temp = 5 degrees instead of ice, would that be risky ?

Bert - 6-2-2015 at 05:24

If you have ENOUGH cold water, and the reaction vessel configuration and rate of addition allow the heat to be removed, it will be possible to prevent a run away. Determining in advance HOW MUCH ice and WHAT SHAPE/SIZE reaction vessel is what all the engineering math earlier was about. You only need to keep the charge below someplace around 20 C, but colder gives more margin for error-

The key difference in starting with cold water: there is a substantial amount of energy required to MELT the ice. You're going to need substantially MORE cold water than ice, even comparing liquid water at .001 ºC, to solid ice at -.001 ºC.

Water heat of fusion: 334J/g (334kJ/kg)

See area "B" of graph below:




image.jpg - 22kB

The diagram shows the uptake of heat by 1 kg of water, as it passes from ice at -50 ºC to steam at temperatures above 100 ºC, affects the temperature of the sample.
E: Steam absorbs heat and thus increases its temperature.

D: Water boils and absorbs latent heat of vaporization.

C: Rise in temperature as liquid water absorbs heat.

B: Absorption of latent heat of fusion at 0 ºC,

A: Rise in temperature as ice absorbs heat.

from-http://www.physchem.co.za/Heat/Latent.htm

[Edited on 6-2-2015 by Bert]

Hennig Brand - 6-2-2015 at 07:19

As Bert pointed out there is a phase change when ice changes to water, which absorbs a lot of heat/energy without temperature change. It takes about the same amount of energy to melt a kg of ice as it does to raise the temperature of a kg of water from 0C to 80C. Heat transfer was through the glass sidewall of the spherical vessel in the example. The ice was to go in the ice water bath surround which the heat of nitration and heat of dilution was transferred to (through the glass sidewall).

ecos - 6-2-2015 at 08:46

ok , i got the message :) thanks all

I always nitrate glycerin at 5 degrees, so it would be an advantage to cool it more before pouring it in the ice path.
they state in referencing "the mixture is added in one portion to crushed ice" or "the mixture was added to ice path in one shoot"
why they use the wording : "one portion or one shoot" ?

[Edited on 6-2-2015 by ecos]

Hennig Brand - 7-2-2015 at 08:54

When and if I try a large batch such as was described by the above calculations, I will use a small submersible centrifugal fountain/pond pump to circulate the ice water in the ice bath surrounding the nitration vessel (these can be purchased as table top fountains for 10 to 15 dollars). The nitration mixture will be stirred with a Teflon paddle powered by drill. Keeping both the nitration mixture and ice bath well mixed will provide a near maximum rate of heat transfer, since the temperature differential from one side of the reaction vessel sidewall to the other will be kept at near maximum. Forced convection allows much greater rates of heat transfer than natural convection.

Hawkguy - 7-2-2015 at 09:41

Quote: Originally posted by Hennig Brand  
The nitration mixture will be stirred with a Teflon paddle powered by drill.


A drill? Sounds kinda messy? Maybe you should just try a little motor scrapped from a toy or something...

Metacelsus - 7-2-2015 at 10:01

Would that be any less messy? Besides, drills have built-in speed control, and with the right equipment, the drill will be out of the path of the acid.

Bert - 7-2-2015 at 10:46

Overhead stirrers are nice for stuff that bogs a magnet, or as in this case where a cooling/heating bath interferes. I have used a drill & hose clamps etc. as well, trying to buy a dedicated outfit now just to not have to mess with speed control & mounting.

Hennig Brand - 8-2-2015 at 17:07

Overhead stirrers can also be run so that they don't contact the sides or bottom of the reaction vessel, which can be an advantage in safety with friction sensitive materials.

I don't think there needs to be any mess. If there is significant splashing it likely means the stirrer is going too fast or the stirring paddle, or other attachment, is not of the right type or some other mix-up. Cordless drills can be modified for accurate speed control easily, since they use a DC motor. They can also be made to run from a mains fed power supply. Even regular corded drills normally have brushes, as far as I know, so they too can be easily speed controlled by simply changing the voltage supplied to them or better yet using a triac type speed controller. I found a hobby speed controller circuit here:
http://www.electroschematics.com/444/motor-speed-regulator-w...

"This triac-based 220V AC motor speed controller circuit is designed for controlling the speed of small household motors like drill machines. The speed of the motor can be controlled by changing the setting of P1. The setting of P1 determines the phase of the trigger pulse that fires the triac. The circuit incorporates a self-stabilizing technique that maintains the speed of the motor even when it is loaded.


220VAC Motor Speed Controller Schematic

motor-speed-regulator-schematic.gif - 21kB


For example, when the motor of the drill machine is slowed down by the resistance of the drilled object, the counter-EMF of the motor also decreases. This results to a voltage increase in R2-P1 and C3 causing the triac to be triggered earlier and the speed increases accordingly."


[Edited on 9-2-2015 by Hennig Brand]

Hennig Brand - 14-2-2015 at 05:50

Just realized I messed up the calculation for the amount of ice needed on the last page of this thread. The amount of ice required was based on the mass of glycerine nitrated, assuming complete nitration, and I calculated as if it was based on the amount of NG.

Quote: Originally posted by Hennig Brand  


An ice water bath is an excellent way to cool a nitroglycerine nitration reaction mixture.

Water heat of fusion: 334J/g (334kJ/kg)

Mass of ice needed for cooling per gram of glycerine nitrated assuming no heat transfer to surroundings:

(1.43kJ/1g Glycerine) * (1kg Ice / 334 kJ) = 0.0043 kg Ice/1g Glycerine Nitrated (4.3g Ice/g glycerine nitrated)

Ice needed for synthesis of 1L of NG = 1000mL(1.6g/mL)(4.3g Ice/g glycerine) = 6880g of Ice (6.88kg of Ice)
This is assuming no heat transfer from the surroundings! In reality the amount of ice required could be much more.



Here is the correction:

An ice water bath is an excellent way to cool a nitroglycerine nitration reaction mixture.

Water heat of fusion: 334J/g (334kJ/kg)

Mass of ice needed for cooling per gram of glycerine nitrated assuming no heat transfer to surroundings:

(1.43kJ/1g Glycerine) * (1kg Ice / 334 kJ) = 0.0043 kg Ice/1g Glycerine Nitrated (4.3g Ice/g glycerine nitrated)

Ice needed for synthesis of 1L of NG = 1000mL(1.6g/mL) / (227.09 g/mol) * (92.09382 g/mol) * (4.3g Ice/g glycerine) = 2790g of Ice (2.79kg of Ice)
This is assuming no heat transfer from the surroundings! In reality the amount of ice required could be much more.

What a difference a little slip can make!

nux vomica - 14-2-2015 at 18:10

Ive bought these of ebay they work a treat controlling heating elements and ac brushed motors. cheers nuxy.

http://www.ebay.com.au/itm/Adjustable-Voltage-Regulator-AC-S...

[Edited on 15-2-2015 by nux vomica]

PHILOU Zrealone - 15-2-2015 at 06:58

Just my 50 cents as a side note!

Determination of organic alkanic halogens can be done with AgNO3 (in methanol or aceton...avoid ethanol at all costs because of the risk of formation of sensitive Ag-O-N=C (silver fulminate)!)
-Reactivity goes in the way I > Br > Cl
-Primary halogen react faster
R-X + AgONO2 --> R-ONO2 + AgX
-Secondary halogen react at a slower rate or with mild heating
R2CH-X + AgONO2 --> R2CH-ONO2 + AgX
-Tertiary doesn't react
R3C-X + AgONO2 -//-> R3C-ONO2 + AgX
-AgX can be recyled by electrolysis or by photolysis into metalic Ag and X2; eventually by cementation upon contact with metallic copper.
-Chloride can be converted into bromide and iodide by reacting R-Cl with saturated NaBr or NaI aceton solutions (NaCl precipitates out).
-Polyhaloalcanes can be done OTC from polyols with concentrated HCl, ZnCl2 and heat.

From this it is obvious that glycol dinitrate (EGDN) and propantriol trinitrate (NG) can be made by simply mixing Cl-CH2-CH2-Cl, or ClCH2-CHCl-CH2Cl aceton and slight excess of AgNO3...with NO HEAT NOR RUNNAWAY RISKS!

This technique must be applicable to higher nitrate esters like PETN from (C(CH2Cl)4), ETN from 1.2.3.4-tetrachlorobutane (chlorinated erythritol), pentachloropentane (chlorinated xylitol), hexachlorohexane (chlorinated mannitol or sorbitol), .... and to make PVN from low molecular PVC.

The only limitation for most is the cost of AgNO3... but I personnaly own about a kg of that stuff and that is the reason why I thought about this.

Last non negligible aspect... if I-CH2-CH2-I is more suitable than Br-CH2-CH2-Br itself better than Cl-CH2-CH2-Cl, the prevalence of Iodide is limited by its cost/availability over Bromide and Chloride and by the unstability of vicinal iodides...
1.2.3-triiodo-Propane easily turns into allyl iodide and iodine!
I-CH2-CHI-CH2-I ==> CH2=CH-CH2-I + I2


[Edited on 16-2-2015 by PHILOU Zrealone]

Hennig Brand - 15-2-2015 at 10:05

Very interesting method you have laid out for us. I probably have a few hundred grams of silver nitrate, but I hang onto it for silver azide, acetylide, fulminate, etc. Though interesting the amount of stages and expensive materials involved in the process including recycling is a lot in comparison to the traditional approach using mixed acid and glycerine. I don't think that there is any need of a runaway even with up to a 1L NG batch size as long as a few basics are understood (I apologize for the lack of care employed when going through the numbers the first time). I am kind of looking forward to attempting a relatively large batch at his point now that things are quantified reasonably accurately with regards to heat.


[Edited on 16-2-2015 by Hennig Brand]

PHILOU Zrealone - 15-2-2015 at 10:46

The other avantage of AgNO3 method is that no concentrated HNO3 or H2SO4 are needed.

Last but not least danger of scaling up the HNO3/H2SO4 method for nitrating polyols comes from:
-While the volumes increases, the relative cooling surface decreases
Just as an example consider a cubic reactor; the volume is full, but the active cooling happens by 5 sides, upside is left to open air (natural cooling is considered ineffective).

Height= 1 cm
V= 1 cm³
Cooling surface= 5 cm²
S/V geometrical cooling efficiency= 5

Let us double the dimensions
Height= 2 cm
V= 8 cm³
Cooling surface= 20 cm²
S/V geometrical cooling efficiency= 2,5

One more doubling
Height= 4 cm
V= 64 cm³
Cooling surface= 80 cm²
S/V geometrical cooling efficiency= 1,25

And another doubling
Height= 8 cm
V= 512 cm³
Cooling surface= 320 cm²
S/V geometrical cooling efficiency= 0,625

In the industry such effect have had severe consequences and have resulted in most large chemical incidents. Scaling up from the lab-scale to pre-pilot plant and full pilot plant must be studied in details. Even a simple doubling has lead to lethal explosions.

-Mixing becomes less efficient and hot spots can easier happens...
Because you cannot increase the speed of mixing by much...cavitation will occure and with those the risk of detonation of the formed NG increases.

-The rate of addition of reactants must be addapted to the scaling up the larger the batch; the slower the addition.

[Edited on 15-2-2015 by PHILOU Zrealone]

Hennig Brand - 16-2-2015 at 04:41

I have been through a lot of the important heat transfer calculations in the last half a dozen posts or so. I don't mean to sound arrogant or careless, but I think I understand the cooling and mixing requirements better than most now. You make a good point about mixing requirements, and I think the idea would be to use a very large slow moving paddle or some other stirring attachment. Large and slow moving so that good mixing is achieved but also very gently.

PHILOU Zrealone - 16-2-2015 at 06:12

@Hennig Brand,
I don't put your experience on the line, but it needs to be pointed for less carefull users.

The main problem is that for effective mixing, one usually need a turbulent mixing and not a laminar one...
A slow, gentle mixing at microscale is in fact quite turbulent due to wall effects but at higher scales it will be close to laminar and will lead to dead zones (unproper mixed zones) very prone to hot spots...
Shock sensitivity of NG precludes the use of faster mixing rate (rpm).

So while general macroscale thermic indicators might prove to be on the safe temperature side...locally hot spots will form with increased reaction rate (reaction rate and heat generation is quadratic as a function of temperature) so hot spots will generate local runnaway that may very fast propagate to the the full batch.
-->In the case of large NG batch because of the inherent sensitivity of NG to shock/heat... this calls for serious troubles.

In other polyols nitration, the mixing may also induce friction of the polyol polynitrate ester cristals.

Other aspects for mixing of explosive materials:
-In some cases mixing of non polar solvents may induce static electricity build up and high voltage sparks inside the fluid.
-If viscosity is high, mixing at high speed will convert kinetic energy into friction energy and transfer a good deal of heat to the fluid. I have noticed this effect while mixing viscous solutions of silicone oils in ethanol with lab propeller blade at high speed.

Hennig Brand - 16-2-2015 at 16:16

I was planning an using a piece of Teflon sled runner, which would act like a large stir bar except that it would be driven from above by shaft and not from below by magnetic coupling. I already have a powerful cordless drill and power supply and speed control for it, so that much is sorted out. Did you have any suggestions about the type of mixer attachment that would be suitable? I would be pleased to hear any.

PHILOU Zrealone - 18-2-2015 at 06:09

Quote: Originally posted by Hennig Brand  
I was planning an using a piece of Teflon sled runner, which would act like a large stir bar except that it would be driven from above by shaft and not from below by magnetic coupling. I already have a powerful cordless drill and power supply and speed control for it, so that much is sorted out. Did you have any suggestions about the type of mixer attachment that would be suitable? I would be pleased to hear any.

I would use propellers that would induce much trubulence at low speed.
Like multiple propeller blade on a single axis or cheese slices (with holes ;) with different paterns and size to break laminarity on next coming mixing wall)

prop.jpg - 13kB

Or something more complex...like

prop1.jpg - 16kB

But I think complexity is not needed here.

Bert - 18-2-2015 at 08:39

I like this shape, made from HDPE. Should replace metal shaft with Teflon or glass for use in nitration mixtures- Spin in direction that causes fluid to be drawn in from top & bottom, expelled from sides (clockwise as seen from above).

image.jpg - 27kB

ecos - 19-2-2015 at 01:00

So whats wrong about magnetic stirrer?
http://en.m.wikipedia.org/wiki/Magnetic_stirrer

Trotsky - 19-2-2015 at 01:04

That's a cool design, basically the style used in (most?) Compressors today, though wide open like that it obviously wouldn't compress much, and the thin blades would minimize risk of cavitation. Good idea!

Bert - 19-2-2015 at 08:03

Quote: Originally posted by ecos  
So whats wrong about magnetic stirrer?
http://en.m.wikipedia.org/wiki/Magnetic_stirrer


How hard do you want to strike nitroglycerin between hard plastic and glass surfaces? It's not terribly sensitive when wet, but still I would not.

Homemade Overhead Stirrer

Hennig Brand - 19-2-2015 at 13:59

Thanks for the ideas. For now I am going to try and use what I have lying around though.

It isn't beautiful, but it is a good working homemade variable speed overhead stirrer with lots of power and speed. Total cost ca. $26.60 ($10 for second hand 18V cordless drill, ca. $15 for 10mm diameter Teflon rod & $1.60 for mounting hardware). Often times drills in nearly perfect shape like this can be found very cheap or free because the batteries need replacing. It is often more cost effective to simply buy a whole new drill kit than to replace just the battery or batteries. I discovered that cordless drills have very good speed control; all that is required is a way to precisely control the trigger position. The trigger position controls the position of a variable resistor in the pulse width modulator trigger module. The drill also has a high and a low speed setting on the gear head. A c-clamp was found in the junk pile which was originally designed to hold a half ton truck cap on. The c-clamp works very nicely for setting and maintaining trigger position and speed. The trigger mechanism (pulse width modulator) was removed from the drill. A section of regular household extension cord (3m long) was spliced in as an extension between the trigger mechanism (pulse width modulator) and the drill. The useless cells were removed from the battery pack and the pack casing was mounted to the vertical member of the stirrer stand; the drill can be easily attached and removed in this way. The drill is rated as 18V, but works fine from 12V providing all the speed and power needed. The pulse width modulator is rated for 9-24V and 12A. A computer power supply rated for 12V and 12A was used to supply power to the PWM. The stirring blade or paddle is put in the 2L flask lengthwise then turned sideways and threaded to the rod. A much larger paddle can be put through the neck of the 2L flask in this way. Two stirring blades were made which can both be threaded to the end of the rod together if desired. The Teflon rod has a slight bend to it, so I will be looking for something better such as a steel rod coated with Teflon or HDPE. I would imagine that HDPE plastic tubing could be used to coat or slide over a straight steel rod. A tight friction fit where the rod and paddle are threaded together could make a decent seal and prevent acid from reaching the steel rod. It is very easy to form a vortex, even at about medium speed, but the bent shaft makes higher speeds unstable. The blade is also not balanced which could be a problem at high speed. When both blades are attached together they can be installed so that there is better balance.

BTW, the "Teflon sled runner" that I obtained from a scrap yard is actually HDPE (determined by density). Checking density is a good way to help determine what type of plastic one has if it is found as salvage and the identity is uncertain.

A plastic shield could be attached to the shaft, close to the chuck, to prevent most acid vapors from reaching the drill. An exhaust fan with the inlet positioned just above the flask neck would also help prevent acid vapors from reaching the drill.


1.jpg - 259kB 2.jpg - 230kB 3.jpg - 227kB 4.jpg - 422kB 5.jpg - 439kB 6.jpg - 454kB 7.jpg - 208kB 8.jpg - 448kB


[Edited on 20-2-2015 by Hennig Brand]

Hennig Brand - 20-2-2015 at 15:39

Looking at the common stainless steels, it appears as though none are ideally suited for contact with nitration acid though 304 is fair according to several compatibility tables. I picked up an 18 inch long piece of 3/8 inch diameter 304 SS from a local machine shop for about $3. The end of the SS rod was threaded with a die. The HDPE stirring paddles were drilled and tapped and made balanced by cutting off the bottom lip that the Teflon rod was threaded into earlier. With the relatively straight rod and balanced blade the stirrer can be run at high speed now with only minimal vibration.

The 304 SS will corrode in the mixed acid, but the rate should be very slow especially at the low temperatures of a nitric ester nitration. HDPE is also not an ideal material for nitration mixtures, but it too should degrade relatively slowly especially at the low temperatures of a nitric ester nitration. Also, the contact time is normally fairly brief since nitric ester nitrations are normally relatively rapid.

Here are a few pictures. The flask is 2L and contains water. The last picture is of the stirrer running at about 80% of full speed.

1.jpg - 466kB 2.jpg - 418kB 3.jpg - 440kB 4.jpg - 448kB


[Edited on 20-2-2015 by Hennig Brand]

PHILOU Zrealone - 22-2-2015 at 05:53

HDPE and PP should withdraw H2SO4/HNO3 at cold temperature...
but upon heating they might loose integrity by softening-melting.

Oxydation and nitration will only occure at high temperature.
The presence of colourizers and charge agents might lower the resistance...so better use transparent colorless plastic.

Aluminium and Iron will withdraw concentrated HNO3 alone but maybe not in admixture with H2SO4: there exists a passivation effect of HNO3 towards those metals (probably due to surfacial special oxyd layer formation) ....passivation of iron stops as soon as in contact another metal like copper.

[Edited on 22-2-2015 by PHILOU Zrealone]

Hennig Brand - 22-2-2015 at 08:11

Yeah, using uncolored white HDPE would probably be best, you are right.

I have used the same HDPE as a stirrer blade in an ETN synthesis here: http://www.sciencemadness.org/talk/viewthread.php?tid=7209&a...

At the time I thought it was Teflon, since that was what I was told it was. In retrospect it would have been very easy to tell the difference since the densities are very different. The HDPE appears to be unaffected after being used twice, for about 3 hours total contact time, in a nitration acid made by adding ammonium nitrate to sulfuric acid. I didn't check the weight of the HDPE before and after, however, which would have been informative (something to keep in mind this time around perhaps).


Also, HDPE appears to be what the dark gray bushing used on the receiver flask was made of here: http://www.sciencemadness.org/talk/viewthread.php?tid=15676&...

The HDPE plastic bushing has been exposed to nitric acid vapors for several hours at this point with only slight blistering if any observed on the end exposed. Once again, taking the weight before and after would have been a good idea.


Here is some compatibility ratings taken from, http://hayata.com/products/chemicalCharts/mo.htm. There are many other sites giving similar ratings. "Ratings of chemical behavior listed in this chart apply at a 48-hr exposure period."

................................................Stainless Steel 304.....Stainless Steel 316
Chemical....................................Compatibility.............Compatibility
Nitrating Acid (<15% HNO3)........ C-Fair .....................D-Severe Effect
Nitrating Acid (>15% H2SO4)....... C-Fair ....................C-Fair
Nitrating Acid (<1% Acid)............ C-Fair.................... A-Excellent
Nitrating Acid (<15% H2SO4)....... C-Fair.................... C-Fair
Nitric Acid (20%)........................ A-Excellent............. A-Excellent
Nitric Acid (50%)........................ A-Excellent............. A-Excellent
Nitric Acid (5-10%) .....................A-Excellent.............. A-Excellent
Nitric Acid (Concentrated)............ A-Excellent.............. A-Excellent


[Edited on 22-2-2015 by Hennig Brand]

Hennig Brand - 22-2-2015 at 09:09

Found a decent compatibility table with lots of information for nitration acids in contact with different stainless steels at various concentrations and temperatures. From this table it looks as though 316SS is actually better than 304SS is some cases, though both appear to be very good at low temperatures.

The pdf containing the compatibility tables is attached below. The ratings include a general corrosion rate as well.

"
0 = resistant to general corrosion (mass loss rate <0.1 g/h · m² corresponding to a corrosion rate < 0.11 mm thickness reduction/year)
1 = slight susceptibility to general corrosion, suitable for some applications (0.1 – 1.0 g/h · m² corresponding to 0.11 – 1.10 mm thickness reduction/year)
2 = low resistance to general corrosion, unsuitable for virtually all applications (1.0 – 10.0 g/h · m² corresponding to 1.1 – 11.0 mm thickness reduction/year)
3 = no resistance to general corrosion (>10.0 g/h · m² corresponding to > 11.0 mm thickness reduction/year)
The following warning is provided for the major forms of localised corrosion
L = risk of pitting, crevice corrosion or stress-corrosion cracking, even in resistance class 0
"

A jpg of the nitration acid part of the table was made as well. Column 4 and 5 refer to 304 and 316 stainless steels respectively.

Stainless Steels & Nitration Acids Compatibilities.jpg - 175kB

Attachment: Material Compatibility Tables.pdf (213kB)
This file has been downloaded 451 times


Trotsky - 23-2-2015 at 06:03

Yeah in most places I've worked HDPE is generally referred to as Teflon, few know the difference because it's not particularly important for most uses.

Bert - 23-2-2015 at 06:54

I particularly like the specifications of those last 3 corrosion resistant grades- N08904 and similar. Did a quick Google search.

1.4465 X1CrNiMoN 25-25-2 SEW400

1.4539 X1NiCrMoCu 25-20-5 10088-2 N08904

1.4565 X2CrNiMnMoNbN 25-18-5-4 SEW400 S34565


Plenty of suppliers for N08904 tube and bar stock on line, nothing for smaller pre fabricated vessels/reactors. Anyone experienced with the metallurgy of this class of stainless, can they be MIG welded and the weld retain the desired corrosion resistance? I suck at TIG!

Praxichys - 23-2-2015 at 06:58

Nobody here has done it on an amateur scale so I thought I'd bring it up: What about stirring with compressed air?

Clean dry air from a small air compressor (maybe for a fish tank?) and a sizeable CaCl2 drying bottle is blown at low pressure through a glass tube attached to a 2-neck flask through a thermometer adapter. There are no moving parts to contact anything and create a dangerous friction situation, and the sparging effect can help reduce the buildup of dissolved nitrogen oxides. A reflux condenser is fitted to help mitigate the escape of nitric acid. The rather closed nature of the setup also allows waste fumes to be conveniently routed out of the room.

If you rig it right, the air tube could also be used to deliver the glycerin, with the application of a female T-joint (one ground glass and two hose barbs) fixed to the bottom of a pressure-equalizing addition funnel, to deliver the glycerin into the airstream.

This setup would clearly only work for nitration baths using mixed acids. The viscosity of cold H2SO4 and a nitrate salt would probably make air-stirring ineffective.

Bert - 23-2-2015 at 08:17

Kind of like this?



image.jpg - 314kB

ecos - 23-2-2015 at 08:41

Hi Bert,

I start to feel that you like this figure a lot :)

Praxichys - 23-2-2015 at 10:19

Quote: Originally posted by Bert  
Kind of like this?


Yes, I saw this several posts back. I believe it is also the method many manufacturers used industrially. I have not seen anyone actually use this technique in an amateur laboratory though.

It may be worthwhile investigating since amateur stirring setups are usually rigged and may involve running heavy brushed motors on cobbled-together stands, teetering over pools of high explosives/flammable liquids as they spark away, wobbling occasionally to strike the stirrer against glass...

Air stirring is also cheap. I have a fishtank pump for air sparging that cost me $7, and the tubing usually comes free with the pump.

Hennig Brand - 23-2-2015 at 12:07

Bert, I was interested in those other special super low corrosion rate stainless steels as well. The local fabrication shop here has offered to try and order me whatever I want if I give them some numbers. For now they have 2' of 3/8" 316 waiting for me to pick up. It is a little more expensive than 304, but not that much (ca. 20% more).

I was thinking of using a bushing (Teflon or HDPE) that would fit in the neck of the flask. This could allow the drive shaft to pass through and still maintain a decent seal. A Teflon or HDPE bearing, which could be as simple as a hole in a block of either plastic, could be positioned above the flask and could be part of a frame or flask housing/compartment, positioned below the drill (motor and gear head assembly), built to take strain off of the drill bearings and gears and provide protection for the delicate glass and possibly sensitive explosive contained within from falling objects, etc. If the stirrer blade is designed and positioned properly one should be quite certain that it will not contact the sides of the vessel while stirring.

I have seen it stated in the literature that compressed air was used in the past at least on the small scale. I don't think normal sized pet store aquarium air pumps would put out the volume and pressure needed for the 2L flask, with about 1L of fairly viscous contents, I am using. Seems to me those pumps put the air out in little pulses as well, not really in a continuous stream like from an air compressor with pressurized storage tank.

The other big advantage of the overhead stirrer, probably the most important, is the ability to provide good mixing to very viscous mixtures. I think it is going to be fantastic for solid nitric ester nitrations. A glycerine nitration with mixed acid would put very little load on the drill which is also a good thing.

Even a common household fan could often be used to prevent the buildup of flammable gases and vapors and keep the concentration in air below the flammability and/or explosive limits.


[Edited on 24-2-2015 by Hennig Brand]

Trotsky - 26-2-2015 at 00:22

Do you have a drill press, by any chance? With the stirrer in the drill running at low speed, lower and lock it into place, and when you're done, raise it up and release. When making NC I've always just put it in a jar and slowly rotated it periodically to make sure everything was getting evenly nitrated, and I've gotten decent results, but having something like that slowly spinning the mixture would help a great deal, I'm sure.

Hennig Brand - 26-2-2015 at 18:17

A drill press is an option. I like how most drill presses are more robust than cordless drills and have the motor and most other sensitive parts not directly over the chuck. Cordless drills do have a lot of nice features though, such as an adjustable torque limiter, basically infinite speed control (PWM), and an easy to use keyless chuck. Cordless drills aren't really designed for continuous duty, but I think the loads are small enough for my purposes and will be fine.

Regarding stainless steel corrosion in nitration acids, the corrosion rate of a rotating shaft will be much higher than for a storage tank, of a given SS, holding the same acid at the same temperature. Of the common stainless steels 316 is definitely a better choice than 304, but I am still going to try out the 304 shaft for low temperature nitric ester reactions. I found a couple of well known alloys (stainless type steels) that are much more corrosion resistant than 316. They are, of course, less commonly available and more expensive as well.

Hastelloy
http://en.wikipedia.org/wiki/Haynes_International

Alloy 20
http://en.wikipedia.org/wiki/Alloy_20

Attached is a data page for Alloy 20. It discusses welding and other processes as well. I am not a welder, but I am fairly certain that most if not all the stainless steels can be welded. From reading it seems that all types/methods of welding are used dependent on the application. TIG is of course know as the "Cadillac of Welding" if I remember correctly. I have seen welding rods that were stamped "316", and rods of other alloy compositions can be obtained as well.

A big problem that can occur when welding stainless steels is "weld decay". It is common to see stainless steels with a line of corrosion running beside the weld a small set distance from the weld. I made the attached pdf regarding weld decay from the following webpage, which seems to have done a good job of explaining the phenomenon. I hope they don't mind my including it here too much.

http://www.corrosionclinic.com/types_of_corrosion/weld_decay...

There are techniques to prevent weld decay, such as heat treatments and also some alloys, particularly those with low carbon content, are much less susceptible as well.



Attachment: Alloy 20 Data Sheet.pdf (139kB)
This file has been downloaded 349 times

Attachment: Weld Decay Explained.pdf (440kB)
This file has been downloaded 470 times


[Edited on 27-2-2015 by Hennig Brand]

nux vomica - 27-2-2015 at 18:51

We only use 316L SS for the internal wetted parts of our pharmaceutical tanks after we double weld the seams and dress and sand them then we have to polish them to .4 RA (mirror finish) after its given the ok by the inspector its passivated internally to smooth the surface off even more, then you get the tank back in 6 months to a year to referb it cause the dumb factory workers use metal mixing poles and scratch the inside up :mad:. nuxy.

304 Stainless Steel and HDPE Held Up Well In Nitration Acid

Hennig Brand - 3-3-2015 at 18:46

I will just give a brief description here and possibly later something more thorough with more pictures in an ETN thread. A mixed acid was made from 600g of ammonium nitrate, 900mL of 91% sulfuric acid and was used to nitrate 150g of erythritol in a 2L flask. Mixing was provided for nitration, dilution and washing stages by the previously built overhead stirrer. The HDPE blade and 304 SS shaft were in contact with the mixed acid for about 2 hours and there appears to be no visible damage whatsoever. The tool marks, which are visible in the picture, are the result of my sloppy work earlier during construction. The temperature of the nitration never went above 15C which is ideal from a corrosion prevention perspective.

Addition of the 150g of erythritol was done over the course of about 30 minutes. No supplemental cooling was used. The ambient temperature was about -5C, which is a different situation entirely from performing the reaction in the summer with an ambient temperature of +30C for instance. Using this type of mixed acid and coarse crystals of erythritol (about the size of granulated white sugar) this reaction is very easy to control; very slow and gentle if a little care is used. Supplemental cooling or slower erythritol addition would be required in a hotter environment.

It is very possible, and would not be much more difficult, to make a pound of ETN at a time with this arrangement. A 3L or larger flask should be used, however, and a 20L pail should be used for dilution and washing as well.


3.jpg - 432kB 6.jpg - 327kB

9.jpg - 197kB 13.jpg - 231kB


[Edited on 4-3-2015 by Hennig Brand]

markx - 3-3-2015 at 23:52

Impressive batch and a very cool stirrer system ;) What was your yield if you don't mind me asking? I've never scaled an ETN synthesis to this level and it would be interesting to know how it looks in terms of process yield.

Hennig Brand - 4-3-2015 at 06:28

Thanks, I know that you like making equipment too. If I know you though, construction would likely have been a little neater. :)
Still drying the product, but I will take a dry crude weight before recrystallization and post it here. I lost at least a small amount during filtering. Regular coffee filters aren't really practical at this scale, so a cloth filter (piece of old undershirt) placed in a large colander was used. During filtering, it is the material which builds up on the membrane that does most of the filtering not the filter membrane itself. When I first started filtering some fines went right through the filter, but once a small amount built up over the larger holes almost none passed through (only clear liquid could be seen passing). The correct procedure would have been to collect what passed through the filter until the filtrate was clear and then pass the filtrate which was collected up until then back through the filter to collect any fines that initially passed through. The yield still looks pretty good and it won't be long until it is dry.

markx - 4-3-2015 at 11:07

I'm not a fan of loose wire bundles...that much is true :D
But then again I certainly do lack the capacity and determination for achieving perfection. Preferences may vary wildly and in the end functionality is the real judge of success, I guess...
Btw, are you drying your batch before recristallisation? I've found this practice to be unworthy and a waste of time in case etn is involved. One can just squeeze the batch more or less dry between paper towels or other suitable absorbant media and then go on dissolving it in preheated alcohol of choice. Works like a charm and is a great time saver...not to mention the slightly raised safety of handling a damp batch...and it will not spill so easily as it sticks together in the damp state.

[Edited on 4-3-2015 by markx]

Hennig Brand - 4-3-2015 at 11:47

It's a work in progress. :D
What I thought I was seeing, a long time ago, was that even small amounts of water significantly reduced the methanol's ability to dissolve the crude ETN (ETN has very low solubility in water). Even slightly damp crude ETN can hold a surprisingly large amount of water. Also, knowing the dry weight makes it easier to accurately determine the amount of solvent needed for the recrystallization to follow. It is something to consider though, since it is a pain to dry the crude product, which is very fine and not as crystalline, clumpy and with more hydroxyl groups left unnitrated as well as at least a small amount of acid contamination which all make drying more difficult. The recrystallized material is always much easier to dry I find.


[Edited on 4-3-2015 by Hennig Brand]

Hennig Brand - 5-3-2015 at 14:33


The following solubility data was taken from, Characterization of Erythritol Tetranitrate. Part I: Physical Properties by Matyas et al.

Table 1. Solubility of ETN in water.

Temperature [Degrees Celsius].......... 5........ 20........ 40..... 60........80
Solubility [mg] ETN in 100 mL water... 1.53.... 3.02..... 9.33...26.9... 39.9

Hennig Brand - 7-3-2015 at 06:14

Equilibrium moisture content finally appears to have been reached. Here are a couple of pictures of the dry crude yield. From 150g of erythritol, 240g of crude ETN was obtained.

The crude product was recrystallized, but it will need time to dry. The 240g of crude product was added by the spoonful to about 720mL of methanol which was previously brought almost to the boil. With the exception of a sub gram quantity of solid material all material dissolved within seconds. A hot filtration was performed, but because of the simple filtration apparatus and a -15C ambient temperature rapid cooling caused the filter to clog when the process was only about 2/3 complete. Nearly all material was recovered in spite of this, but it was inconvenient to say the least. There is a big difference between processing 24g of ETN and 240g! I need to develop more finesse in the purification part of the process that much is evident. In this particular case a hot filtration hardly seemed worth it given the tiny amount of undissolved material, especially if not properly equipped to do one. The undissolved solid material maybe could have been removed some other way.


1.jpg - 233kB 2.jpg - 416kB


[Edited on 7-3-2015 by Hennig Brand]

Issues Associated with ETN Recrystallizations from Methanol

Hennig Brand - 12-3-2015 at 17:13

Performing the ETN synthesis described in the last few posts has caused me to remember a few things about problems associated with ETN recrystallizations from hot methanol and to search for explanations. The following is a U2U exchange with Philou where he gives a good explanation of what is likely happening at the higher recrystallization temperatures.

Quote:
Hello Philou,

I have noticed when recrystallizing ETN from methanol that the solution will turn a yellow-orange color and also that a lot of yield weight will be lost at the same time. This only seems to happen at temperatures approaching the melting point of ETN. For instance, if the methanol is only heated to 50C the solution seems to stay mostly clear and the final yield is greater. The yellow-orange material produced can be fairly easily washed from the precipitated ETN, but when not well washed it was noted that as the ETN was drying there was an acrid, irritating to the eyes and nose smell which came from the sample on close inspection.

I believe the ETN or lower nitrates are decomposing. Rosco suggested maybe transesterification when I mentioned it to him. Do you have an idea about what is happening?

Thanks,

Hennig


Hi HB,
Feel free to post this into your tread!
Yes Rosco is right transesterification seems plausible reason.
Usually it has to be catalysed by a base or an acid but owing to the "high heat" involved in your recrystalization process there are two concomittant process at work:

1°) Due to the heat, the equilibrium is set faster and some CH3-ONO2 is formed while trinitroerythritol (hydroxy in position one or two?) is formed; usually nitration or halogenation occurs faster at the external CH2OH what would tend to mean that the internal CHOH are more hydrolysable (or methanolisable) and would exchange faster their nitrate, so following me it is OH in position 2. Then the hydroxytrinitroerythritol is more water of methanol soluble and would disfavour correct crystallization of your ETN.

2°) The traces of CH3-ONO2 are hydrolysed or oxydised by the too high a heat yielding HNO3 and NxOy with CH2=O (formol-acrid smell), HCO2H (formic acid) and CO2 + H2O. Then acidic HNO3 and HCO2H will help further catalysis for transesterification. The NxOy will then oxydise some of the hydroxytrinitroerythritol into a ketonic variant more prompt to hydrolysis of the viccinal nitrate ester groups and thus accelarating the decay. End Quote


In the past if the recrystallization was done at the lower temperature, typical yields were normally about 1.4g of recrystallized product per gram of erythritol, whereas yields could go as low as 1g of recrystallized product per gram of erythritol if the recrystallization was done close to, or at, the boiling point of methanol. I would need to do more tests, but I remember from half a dozen or more smaller scale syntheses, done in the last few years, that even lowering the methanol solvent temperature to 50C would prevent all or nearly all of the yellow-orange color and yield loss. Lower solvent temperatures will mean that a certain amount more solvent will need to be used however.

The following picture shows the solution of 240g of crude ETN in methanol which had been carelessly let boil for 5-10 minutes.

Botched ETN Recrystallization.jpg - 453kB


[Edited on 13-3-2015 by Hennig Brand]

ETN: Recrystallized Yield & Melting Point Determination

Hennig Brand - 14-3-2015 at 09:03

Equilibrium moisture content was again reached and the recrystallized yield is better than I predicted. From the 150g of erythritol started with, 205g of recrystallized ETN with a melting point of ca. 60-61C was obtained, or about 1.37g of high purity ETN per gram of erythritol started with.

The plate on the left, in the attached image, holds the ETN which precipitated on cooling and plugged the filter when a hot filtration was attempted (dry weight 82g). The plate on the right holds the ETN which precipitated from the solution which passed the filter, some of which was precipitated by dilution of the methanol with water (dry weight 123g). I suspected that the purity would be low, but surprisingly both samples have basically the same melting point somewhere between 60 and 61C.

A little greater care could have been used to wash the yellow-orange impurity from the recrystallized product.

Despite the fairly decent results this time around, I have definitely noticed in the past that low yields and acrid smelling yellow-orange material production were associated with high solvent temperatures during recrystallization.

Melting Point Determination.jpg - 252kB Recrystallized Yield.jpg - 267kB Precipitated in filter.jpg - 241kB Precipitated after filtration.jpg - 218kB


[Edited on 14-3-2015 by Hennig Brand]

markx - 15-3-2015 at 15:25

For the sake of promoting safe(er) practices I have to note that heating a glass container full of highly flammable and highly explosive liquid directly on a hotplate is not the best of the available options. A preheated waterbath with no active sources of heat around would suit much better for this situation. As we know there has already been a tragic event that happened under the very same conditions and with the same reagents involved. I trust it is our duty to learn from that and take the necessary precautions to prevent the reoccurence of similar accidents to the best of our abilities.... please be safe, fellow experimenters!



[Edited on 16-3-2015 by markx]

Hennig Brand - 15-3-2015 at 16:22

Very true, a preheated water bath would be much safer. Using a glass vessel directly on a hotplate is a little more convenient, but it really isn't worth the risk.

Nitroglycerin - Fast and Effective Residual Acidity Neutralization Using Overhead Stirring

Hennig Brand - 27-3-2015 at 04:44

I have not used the overhead stirrer to make NG yet, but I was just thinking how well it could work for speeding release and neutralization of residual acidy. If no form of agitation is used nitroglycerin will sit as a blob on the bottom of the container of bicarbonate solution and acid neutralization is extremely slow. The overhead stirrer should be an effective and safe way to make the NG blob roll around, exposing fresh surfaces and greatly accelerating acid release and neutralization. The blade of the overhead stirrer can be positioned well away from the bottom and sides of the vessel and its speed can be easily adjusted to that which is most effective and safe.

PHILOU Zrealone - 27-3-2015 at 09:12

In the natural diffusion of the trace acid through the NG to find the inteface with the water basic, there is a gradient of concentration of acid in the NG ("high" in the core of the NG and low close to the interface) and of the concentration of base in the water (high in the core of the solution and low close to the interface).

Forced agitation will speed up the encounter of the acid traces and the base and the profile of concentration will be more constant at all times through the entire NG and the entire water. The interface will be subject to a higher concentration variation without gradient on a short distance.

Hennig Brand - 27-3-2015 at 15:15

What I was thinking though I didn't state it above was that the overhead stirrer blade could be set high, well above the NG sitting at the bottom of the container of sodium bicarbonate solution. The drag forces could be set to give the right amount of NG agitation by controlling the speed of mixing of the water above since drag force depends on velocity. I haven't tried it yet, but it seems to me that it would be gentle and effective.

Tabun - 22-4-2015 at 09:51

Quote: Originally posted by Hennig Brand  
Very true, a preheated water bath would be much safer. Using a glass vessel directly on a hotplate is a little more convenient, but it really isn't worth the risk.


Maybe it's a stupid question but what's the difference between a metal plate with x temperature and a bath with the same temperature?I mean...you can control the temperature with these things and I don't think you're going to turn it to...let's say 100 degrees Celsius to heat something to 50 degrees Celsius.
It's not the same with open flame but with an electric hotplate(or however it's called)...

Molecular Manipulations - 22-4-2015 at 11:04

Quote: Originally posted by Tabun  

Maybe it's a stupid question but what's the difference between a metal plate with x temperature and a bath with the same temperature?I mean...you can control the temperature with these things and I don't think you're going to turn it to...let's say 100 degrees Celsius to heat something to 50 degrees Celsius.

Water and metals have very different heat capacities.
The heat capacity is the amount of heat required to raise the temperature of an object or substance one degree. The temperature change is the difference between the final temperature ( Tf ) and the initial temperature ( Ti ).
Water's heat capacity is much higher than most metals, 4.179 Joules is required to bring the temperature of one gram of 0°C water up to 1°C. Iron's heat cap. is 0.450 J/g at 0°C. Thus water will heat up and cool down much slower than a hotplate of similar mass. There may be other reasons as well, but I'm a chemist, not a energetics/explosives synthesizer (not that you can't be both).:D

Hennig Brand - 22-4-2015 at 19:27

Water provides a very even heat without high temperature "hot spots". Unless pressurized water has a maximum temperature of 100C which is a great safety feature. Water also tends to extinguish combustion even when hot. Hotplates generally have a fairly small heat sink, poor temperature control and not terribly great heat transfer ability, (only contacting the bottom of the flask for starters), requiring that the plate be run at a higher temperature for effective heating. Hotplate temperatures normally fluctuate up and down, sometimes very wildly and often much above the set point temperature (if the set point can even accurately be set). The water bath can be a large heat sink and thermal mass which means it resists sudden changes in temperature well. Even if left on a hotplate a reasonably sized water bath can absorb the temperature fluctuations (energy) from the hotplate and maintain a relatively constant temperature. For extra safety a very large water bath could be preheated and used to perform the HE recrystallization since its temperature can only drop once removed from the hotplate and there is much less chance of explosive coming into contact with a hot surface which could result in an accident (if moved well away). An insulated vessel could prevent the water bath from transferring most of its energy to the surroundings. High temperature surfaces are dangerous especially with ETN since it has such a low decomposition temperature.

KesterDraconis - 7-5-2015 at 18:11

So I recently made nitroglycerin, as the next explosive on a long list to make (I hope to make the next TNT!). I did the hammer test on a brick with about half a milliliter (I made one and a half), and I learned to respect the substance even more when after my third strike (the first two broke the brick into three pieces and didn't detonate it, my third strike was with all my force) that little drop absorbed in a paper towel powdered a good bit of the brick piece underneath it and knocked out my hearing in one ear for a second (I wasn't wearing hearing protection, I thought it would sound like a loud firecracker...). Needless to say, I nearly pissed my pants.

While I am amazed with its power, and have gained a new respect for it, I also want to make more of it. Yes I know contradiction right? I primarily want it though for the purpose of making dynamite. I am wondering, what material could I use where nitrocellulose or blackpowder deflagaration explosion would be sufficient to detonate it , or would something like that only work on pure nitroglycerin?

(trying to stay away from more unstable primaries for the moment, though I will make them in the future, since I nearly have enough money to buy the equipment I want)

Hennig Brand - 8-5-2015 at 14:27

Good thing the whole half milliliter didn't detonate. Even a drop or two detonating is very impressive. The nice thing about dynamites is that in general they require very small quantites of primary explosives to initiate properly. That, and they are cheap, powerful and easy to make. The better primaries are reasonably safe if proper handling procedures are understood and followed.

caterpillar - 10-5-2015 at 17:59

When I was young, in my city an incident with a jealousy man took place. his bride preferred another one. The rejected man visited marriage with a bottle full of NG. Sewing needles flew across the street- one friend of mine found couple of such needles at his window-sill.

ecos - 10-5-2015 at 23:49

Quote: Originally posted by KesterDraconis  
So I recently made nitroglycerin, as the next explosive on a long list to make (I hope to make the next TNT!). I did the hammer test on a brick with about half a milliliter (I made one and a half), and I learned to respect the substance even more when after my third strike (the first two broke the brick into three pieces and didn't detonate it, my third strike was with all my force) that little drop absorbed in a paper towel powdered a good bit of the brick piece underneath it and knocked out my hearing in one ear for a second (I wasn't wearing hearing protection, I thought it would sound like a loud firecracker...). Needless to say, I nearly pissed my pants.

While I am amazed with its power, and have gained a new respect for it, I also want to make more of it. Yes I know contradiction right? I primarily want it though for the purpose of making dynamite. I am wondering, what material could I use where nitrocellulose or blackpowder deflagaration explosion would be sufficient to detonate it , or would something like that only work on pure nitroglycerin?

(trying to stay away from more unstable primaries for the moment, though I will make them in the future, since I nearly have enough money to buy the equipment I want)


NG is easier to made than TNT. TNT is very complex.
NG is much more sensitive and a lot of hazards surround it.
I stopped playing with such things. I only use AN if I need to do something.
DON'T PLAY WITH YOUR LIFE COUNTER :)

Tabun - 11-5-2015 at 03:56

Quote: Originally posted by ecos  
Quote: Originally posted by KesterDraconis  
So I recently made nitroglycerin, as the next explosive on a long list to make (I hope to make the next TNT!). I did the hammer test on a brick with about half a milliliter (I made one and a half), and I learned to respect the substance even more when after my third strike (the first two broke the brick into three pieces and didn't detonate it, my third strike was with all my force) that little drop absorbed in a paper towel powdered a good bit of the brick piece underneath it and knocked out my hearing in one ear for a second (I wasn't wearing hearing protection, I thought it would sound like a loud firecracker...). Needless to say, I nearly pissed my pants.

While I am amazed with its power, and have gained a new respect for it, I also want to make more of it. Yes I know contradiction right? I primarily want it though for the purpose of making dynamite. I am wondering, what material could I use where nitrocellulose or blackpowder deflagaration explosion would be sufficient to detonate it , or would something like that only work on pure nitroglycerin?

(trying to stay away from more unstable primaries for the moment, though I will make them in the future, since I nearly have enough money to buy the equipment I want)


NG is easier to made than TNT. TNT is very complex.
NG is much more sensitive and a lot of hazards surround it.
I stopped playing with such things. I only use AN if I need to do something.
DON'T PLAY WITH YOUR LIFE COUNTER :)


Well...TNG is for sure safer than unstable primaries.Use the gun powder and a lead ball to shoot at the nitroglycerin.The shock should be powerful enough to set it off.I don't know exactly why but I think hiting nitroglycerin does a better job of detonating it than igniting it.

[Edited on 11-5-2015 by Tabun]

Hennig Brand - 11-5-2015 at 07:59

The better primaries are quite storage stable and have sensitivities low enough that they can be safely handled with proper technique. When you say gun powder and lead ball I assume you mean black powder and lead ball, if so it could probably work but might not be reliable. NG will gladly detonate at a lower detonation velocity if not initiated properly. I have never done it, but from what I have read even a .22LR can initiate dynamite at close range, but reliability is not great. Apparently anything much bigger and faster than a .22LR is quite reliable for initiating dynamite. The speed of the bullet has to be above the speed of sound to create a shockwave. However, even a lead ball traveling at 800fps could probably initiate pure NG, but I am not sure what the detonation velocity would be or if it would be consistent and reliable shot to shot.

Tabun - 11-5-2015 at 12:24

Quote: Originally posted by Hennig Brand  
The better primaries are quite storage stable and have sensitivities low enough that they can be safely handled with proper technique. When you say gun powder and lead ball I assume you mean black powder and lead ball, if so it could probably work but might not be reliable. NG will gladly detonate at a lower detonation velocity if not initiated properly. I have never done it, but from what I have read even a .22LR can initiate dynamite at close range, but reliability is not great. Apparently anything much bigger and faster than a .22LR is quite reliable for initiating dynamite. The speed of the bullet has to be above the speed of sound to create a shockwave. However, even a lead ball traveling at 800fps could probably initiate pure NG, but I am not sure what the detonation velocity would be or if it would be consistent and reliable shot to shot.

Yes,I knot TNG requires a detonator to...well,detonate properly but the idea wasn't to detonate TNG but to use it instead of a primer.If you ignite a small quantity it deflagrates,if you hit it it detonates.That makes me think a mechanical shock will do better than heat so if you hit it hard enough it should be at least as powerful as a primary like mercury fulminate.
BTW...by "shooting with BP and lead ball" I mean literally making a detonator good enough for the job.

Hennig Brand - 11-5-2015 at 13:01

Since if improperly initiated NG can have very low stable detonation velocities, and it is brisance which counts the most with initiators, it can be a very poor initiator even compared to mercury fulminate. Also, NG tends not to perform as well in the tiny charge sizes and diameters commonly employed with initiators.

The following was taken from "Military Explosives":

Mercury fulminate detonation velocity at 4.17g/cc is 5400m/s.



NG Detonation Velocity.jpg - 226kB


[Edited on 12-5-2015 by Hennig Brand]

ecos - 11-5-2015 at 23:49

I really don't like to play with NG. I synthesized it twice and had a hard headache but i might do it again in future for discovering shaped charges.

Anway, I didnt see any NG mixture with Al powder :).
I think Al if added to AN or other mixtures it increases the power of detonation a lot.

any reason why we don't use Al powder added to NG , PETN ,... ?

Bert - 12-5-2015 at 03:35

Quote:
I synthesized it twice and had a hard headache


A cup of strong coffee usually takes care of that-

Hennig Brand - 12-5-2015 at 03:39

Adding aluminum powder, up to a certain percentage, does normally increase the explosive power, but it also normally lowers the brisance.

Aluminum power is a relatively expensive fuel, so it is normally not used for general blasting. It definitely can be added to dynamites and ammonium nitrate explosives, etc, and will often significantly increase energy and power. Aluminum is even sometimes added to very oxygen deficient explosives like TNT.

ecos - 12-5-2015 at 10:02


Quote:

Adding aluminum powder, up to a certain percentage, does normally increase the explosive power, but it also normally lowers the brisance.


I was planning to add it to NG/NC mixture. Pure NG has a lot of hazards around it not need to add more.

Adding Al to NG Gel would make it more powerful but I miss how to calculate the correct ratio !


Quote:

Aluminum is even sometimes added to very oxygen deficient explosives like TNT

Oh. i thought you would say if it has excess not deficient !
Al would need oxygen ! where it would get it from ? air?

Hennig Brand - 12-5-2015 at 10:27

The TNT supplies a tremendous amount of heat energy to the aluminum and yes I think for the most part the reaction is mostly with oxygen from the air (oxygen from water in the case of sea mines, etc).

PHILOU Zrealone - 12-5-2015 at 14:22

Aluminium will react with oxygen form O2, CO2, CO, N2O, NO, NO2 and H2O in the explosion gases but also with nitrogen N2... then it will react out of the explosion gases with air (N2 and O2 forming AlN and Al2O3).

Owing to the limitation of the minimal Al particle size (if you go too tiny the superficial oxyd layer becomes too significative vs the active metalic Al) then the speed of burning is limited to deflagration or low order detonation...the effect with a high explosive is like a second boost, a kind of post combustion kick.

Al is more interesting if added in over oxygenated explosives thus with positive OB; but it is sometimes used with oxygen deficient explosives like TNT... Tritonal is such a mix of TNT (80 to 60%) and Al powder (20 to 40%).
The TNT disperse the overheated Al powder in the air making a kind of Fuel Air Explosion because in the phase after the detonation blast the Al bruns with the surrounding air (Nitrogen and Oxygen) generating a big fire ball; then because the air has been "condensed" into solid material AlN and Al2O3; if you have a large enough device, you get an implosion effect (the burned oxygen and nitrogen creates a kind of vacuum that must be filled by the surrounding air outside the second blast).

[Edited on 12-5-2015 by PHILOU Zrealone]

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