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Bender84
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[*] posted on 24-3-2016 at 10:14
NG/EGDN mixture - freezing curve


Hello there!

Does any of you guys have or knows where I could find a relatively up to date freezing curve/ diagram (temperature versus composition) of a NG/EGDN mixture?

For clarity sake, it should look something like the one below (probably):

I would be gratefull for any help.
Best regards.

freezingCurve.png - 37kB
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[*] posted on 25-3-2016 at 05:45


Welcome to scimad!

EGDN addition can lower the FP of NGl to ~-60°.

One might assume the ratio then to be in the range 50/50, but without a graph, it's just conjecture . . .

But EGDN alone should suffice in any cold conditions short of the arctic!

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[*] posted on 25-3-2016 at 08:33


Hi hissingnoise,

Thank you for your kind welcome :)

As far as I know, the 60:40 ratio is the most optimal one, but a graph would definitely help to confirm this.

Also, I'm asking this, because knowing the freezing curve of BG/EGDN one can estimate both the safest and most economical ratio of these two. NG is much cheaper than EGDN and it has much lower vapor pressure (it is less volatile), therefore it is safer for workers (of course not in terms of overall toxicity, but at keeping the TLV below limits). Altering the ratio "just a bit" in favour of NG, gives huge savings, but I it cannot be done without knowing the freezing curve. Safety first.

I was hoping that some of you guys may have seen this curve somewhere or even done such measuring. The only one I saw was over 100 years old :( Another one from different source and done more recently, perhaps would not change anything, but at least I would get some confirmation that the old one is correct.

Cheers.
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[*] posted on 25-3-2016 at 11:39


@Bender84,

1°) Glycerol (propantriol) is normally more or equally expensive than glycol.
What are your arguments in favor of a cheaper NG price vs EGDN one?

2°) If you make a mix of the two, you may think that by the colligative laws, you will reduce the volatility of the two compounds...unfortunately it only works if one of the component is a non volatile compound...so here by opposition you will have a slighly higher vapour pressure of the most volatile component above it...what changes nothing for security or safety.

3°) Also a more volatile compound in the mix will favor tiny bubbles formation inside it what is a call for disaster in the case of NG and EGDN due to the increased shock sensitivity.




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[*] posted on 25-3-2016 at 12:59


Quote:
Glycerol (propantriol) is normally more or equally expensive than glycol.


And EGDN is attractive to any hobbyist not making industrial quantities or stuck in the tropics ─ its lower viscosity giving higher brisance than NGl and its zero OB higher strength!

Added to its easy nitration is its lower sensitiveness, which kinda makes EDGN hard to beat!

Pity about the minor downsides of higher volatility and solubility . . .

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[*] posted on 25-3-2016 at 15:21


As I recall the vapor pressure of EGDN is only slightly higher (5% or something) than NG, I've seen EGDN residue on glassware that didn't evaporate to any noticeable degree in over a week. I don't think it's something worth considering other than in determining how a mixture of NG/EGDN would change over a long period of time due to evaporation.
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[*] posted on 26-3-2016 at 13:04


@All,
Stop recalling and spreading wrong infos!

Check pages 223 to 227 of Rudolph Meyer-Explosives 6th edition. There you find all info about performances, sensitivity and volatility!
RM-6th ed

EGDN is about as sensitive as NG!




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hissingnoise
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[*] posted on 26-3-2016 at 13:32


Quote:
Stop recalling and spreading wrong infos![sic]


Really PHILOU, and what do you see wrong with the info given?

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[*] posted on 26-3-2016 at 14:53


Quote: Originally posted by hissingnoise  
Quote:
Stop recalling and spreading wrong infos![sic]


Really PHILOU, and what do you see wrong with the info given?

Even with the link provided you don't see?
OK...here it comes...

From you:
" its lower viscosity giving higher brisance than NGl and its zero OB higher strength!
Added to its easy nitration is its lower sensitiveness, which kinda makes EDGN hard to beat!"
1°) It is not the lower viscosity that implies higher brisance but a mix of parameters and most of all the better OB (closer to 0) providing a better energy output per kg...
Kast introduced the concept of “brisance value”, which is the product of loading density, specific energy and detonation rate.
Brisance EGDN = 1.48 g/cm³ * 7300 m/s * 121 mt/kg = 1307284
Brisance NG = 1.591 g/cm³ * 7600 m/s * 106.6 mt/kg = 1288965
2°)Impact sensitivity NG = 0.2 N m (so falling weight of +/- 20g from 1 m or 200g from 10 cm!)
Impact sensitivity EGDN = 0.2 N m
So what lower sensitiveness?

From OneEyedPyro:
"As I recall the vapor pressure of EGDN is only slightly higher (5% or something) than NG"

Vapor pressure in mbar as function of T(°C)

@20°C vp NG =0.00033
@50°C vp NG = 0.0097
@80°C vp NG = 0.13
@90°C vp NG = 0.31

@0°C vp EGDN =0.006
@20°C vp EGDN =0.05
@40°C vp EGDN =0.35
@60°C vp EGDN =1.7
@80°C vp EGDN =7.8
@100°C vp EGDN =29
--> EGDN is 151 times more volatile than NG (15100%) at 20°C and 60 times (6000%) more volatile than NG at 80°C!
This is far from "slightly higher" and from "5% or something"




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[*] posted on 26-3-2016 at 16:28


That is quite a difference :o, I'm not sure why I thought they were so similar in terms of volatility... Still, the evaporation rate of EGDN is fairly insignificant. Many seem to be under the impression that it evaporates quickly like water when that is just not the case:P.
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[*] posted on 28-3-2016 at 11:52


PHILOU, it's a bit weird to be arguing with a Brussels resident over the properties of high explosives at this juncture, but bullshit all you want ─ I'm sticking with TL Davis and T Urbanski who, as you should know both contradict Meyer!
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[*] posted on 28-3-2016 at 12:25


Only thing i can add is that 'freezing curve' would be a part of the 'phase diagram' for the substance/mixture.
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[*] posted on 28-3-2016 at 15:00


Quote: Originally posted by hissingnoise  
PHILOU, it's a bit weird to be arguing with a Brussels resident over the properties of high explosives at this juncture, but bullshit all you want ─ I'm sticking with TL Davis and T Urbanski who, as you should know both contradict Meyer!

I didn't know but I must say that all those books contains a lot of errors...
Not more than a week ago, I was reading Urbanski Vol 4 and I was horrified by the mistakes made in formulas and equations...I found those by retro-calculating from tables to come back to the equations but there was always something wrong...then I checked the reference texts and found the mistakes...

Meyer has also mistakes, I don't understand that they don't ask me ;) or a real chemist to check for their 6th edition (I have the 4th in paper book bought with my pocket money at the age of 19 and the same mistakes comes back)...maybe I should propose to peer review it :D
But Meyer works with numerical data from german or conventional international testings...so I'm more keen to follow their point of view.

Also why would methyl nitrate be very sensitive; then why would ethyleneglycol dinitrate be unsensitive; and then again propantriol trinitrate be sensitive... while passing from n= 1 to 3 in H-(CHONO2)n-H?
H-(CHONO2)1-H = CH3ONO2
H-(CHONO2)2-H = O2NOCH2-CH2ONO2
H-(CHONO2)3-H = O2NOCH2-CHONO2-CH2ONO2

for Meyer all 3 display IS= 0,2 Nm


[Edited on 28-3-2016 by PHILOU Zrealone]




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[*] posted on 28-3-2016 at 23:36


Hello all,

Thank you very much for the answers :)

@PHILOU

Quote:

Glycerol (propantriol) is normally more or equally expensive than glycol. What are your arguments in favor of a cheaper NG price vs EGDN one?


Glycerol is about 25% cheaper than glycol in EU mainly due to production of biodiesel. It is created during hydrolysis of fats and it is treated as waste in the process.

Quote:

If you make a mix of the two, you may think that by the colligative laws, you will reduce the volatility of the two compounds...unfortunately it only works if one of the component is a non volatile compound...so here by opposition you will have a slighly higher vapour pressure of the most volatile component above it...what changes nothing for security or safety.


Correct me if I’m wrong, but I think that you can treat NG/EGDN as an ideal mixture, therefore it is subject to Raoult’s Law. So, e.g. for 60:40 mix, the total vapor pressure of the mixture would be 0,0202 mbar (using the vapor pressure values given in Meyer's Explosives 6th ed.), and for the 70:30 mix it will be 0,0152 mbar. You get ~25% decrease in volatility if you increase the NG content by 10%.

Quote:

Also a more volatile compound in the mix will favor tiny bubbles formation inside it what is a call for disaster in the case of NG and EGDN due to the increased shock sensitivity.


I have never seen such phenomenon in my career, neither the people who work decades longer than me in the industry. In conditions we are using the mixture not such thing has ever happened.

And what about the freezing curve? Do you (or anyone who reads this topic) know where I can find such diagram?

Best regards.

[Edited on 29-3-2016 by Bender84]

[Edited on 30-3-2016 by Bender84]
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[*] posted on 2-4-2016 at 03:18
Freezing Points of NG-EGDN Mixtures


I'll take a shot at this.

I have in the past looked for information about the freezing points of different NG-EGDN mixtures and found very little. I spent a bit of time in the last few days searching the internet and have found a few bits of information to get us started on a phase diagram. Some additional freezing point values from reliable sources and/or a freezing point constant for EGDN would help if anyone can find them before I do.


From, "Rock Blasting and Explosives Engineering" (pg. 75):

"
Adding EGDN to NG lowers the freezing point from that of NG from 3C to 13C to -25C to -60C dependent on the mixture ratio."

So, -60C is likely the eutectic point (temperature corresponding to the lowest freezing point mixture) or very close to it.


From Meyer:

NG solidification point: 13.2C
EGDN solidification point: -20C


According to "Nitro-Explosives: A Practical Treatise", technical NG has a melting point normally around 10-11C, and sometimes much lower even, because of the presence of a small amount of di-nitroglycerin. Technical EGDN would of course have a lower freezing point as well because of impurities. We will use the value of 13.2C for pure NG and the value of -20C for pure EGDN for the phase diagram however.



From, "Nitro-Explosives: A Practical Treatise":

"
According to Raoult's law, the lowering of the freezing point caused by _m_ grms. of a substance with the molecular weight M, when dissolved in 100 grms. of the solvent, is expressed by the formula: [Delta] = E(_m_/M), where E is a constant characteristic for the solvent in question. The value of E for nitro-glycerine was found to be 70.5 when calculated, according to Van't Hoff's formula, from the melting point and the latent heat of fusion of the substance. Determinations of the lowering of the freezing point of nitro-glycerine by additions of benzene, nitro-benzene, di-nitro-benzene, tri-nitro-benzene, p.-nitro-toluene, o.-nitro-toluene, di-nitro-toluene, naphthalene, nitro-naphthalene, di-nitro-naphthalene, ethyl acetate, ethyl nitrate, and methyl alcohol, gave results agreeing fairly well with Raoult's formula, except in the case of methyl alcohol, for which the calculated lowering of the freezing point was greater than that observed, probably owing to the formation of complex molecules in the solution. The results show that, in general, the capacity of a substance to lower the freezing point of nitro-glycerine depends, not upon its freezing point, or its chemical composition or constitution, but upon its molecular weight. Nauckhoff states that a suitable substance for dissolving in nitro-glycerine, in order to lower the freezing point of the latter, must have a relatively low molecular weight, must not appreciably diminish the explosive power and stability of the explosive, and must not be easily volatile at relatively high atmospheric temperatures; it should, if possible, be a solvent of nitro-cellulose, and in every case must not have a prejudicial influence on the gelatinisation of the nitro-cellulose."

We now have a freezing point constant for NG of 70.5 to use with Raoult's law for freezing point depression.

More to come........


[Edited on 2-4-2016 by Hennig Brand]




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[*] posted on 2-4-2016 at 03:54


Quote: Originally posted by OneEyedPyro  
As I recall the vapor pressure of EGDN is only slightly higher (5% or something) than NG, I've seen EGDN residue on glassware that didn't evaporate to any noticeable degree in over a week. I don't think it's something worth considering other than in determining how a mixture of NG/EGDN would change over a long period of time due to evaporation.


I guess a possibility is that the stuff you saw not to evaporate was not EGDN but either an impurity or a decomposition product. Stains often look like they contain a lot of material while they actually don't. Compare it with carbonate stains after tap water evaporates, carbonate is there in ppm amounts, but gives a clear stain. I can imaging oily residues give the same effect after EGDN evaporates.
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[*] posted on 2-4-2016 at 10:24
NG-EGDN Freezing Curve


Apparently the equation used is generally most accurate when the solvent (in this case NG) is only slightly diluted, which should be taken into account when considering the accuracy of the blue curve on the right of the eutectic point. The red curve on the left was not made from values calculated using Raoult's law, instead it was made in proportion to the blue curve on the right, which should also be taken into account when considering the accuracy.



NG-EGDN Phase Diagram.jpg - 129kB



Attachment: NG-EGDN Equilibrium Diagram & Spreadsheet.xlsx (50kB)
This file has been downloaded 354 times


[Edited on 3-4-2016 by Hennig Brand]




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[*] posted on 2-4-2016 at 11:51


Well done Hennig, it certainly looks right and is nearly a mirror-image of Bender's attempt . . .

But one would have to assume that to make any savings in that area, very large quantities would be involved!

Interesting . . . ?

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[*] posted on 2-4-2016 at 16:18


Thank you. I wanted this information myself, especially seven or eight years ago or so when I did most of my NG and EGDN experimenting, but never put much energy and time into tracking it down. Now seemed like a good time.

Edit:
Also, I should have called the graph a freezing curve or equilibrium or phase diagram not freezing points since it is a continuous curve with an infinite number of points. I just fixed the title of the graph and the last posts title.


[Edited on 3-4-2016 by Hennig Brand]




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[*] posted on 3-4-2016 at 10:54
NG/EGDN Vapor Pressure Data, etc


The following document contains vapor pressure data, on page four, for NG and EGDN at 30, 40 and 50C as well as calculated vapor pressure values for 10, 20 and 30% EGDN in NG/EGDN mixtures at those temperatures. I didn't bother so far, but it could be useful for someone wanting to make comparisons and see how similar results from Raoult's law are in this case. Raoult's law may be what was used to obtain the calculated values in the document anyway. The values could probably be used to obtain a reasonably accurate curve/equation too.

Attachment: Characteristics of Non-Military Explosives.pdf (2.9MB)
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[Edited on 3-4-2016 by Hennig Brand]




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[*] posted on 7-4-2016 at 12:29


Thank you, Henning Brand! :)

This helped a lot! Today we have discussed your results. We agreed that your calculations are close enough to the phase diagrams we own :) It also corelates well withour experience and knowledge. Unfortunately it also ultimately dashed our hopes to increase the NG content above 60% :) Above that concentration, the mixture has a relative high freezing temperature. Increasing the content of EGDN is not an option due to the high volatility of the substance (risk of exceeding the TLV).

Anyways, I would like to share with you one of the two diagrams we own. Perhaps I will be able to post the second diagram later. I had to digitize it due the bad quality of the scan I received. It is not the one that is 100 years old. This diagram was done more recently by Polish scientist prof. Syczewski.

Best Regards.

ng-egdn-phase-diagram.png - 90kB
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[*] posted on 8-4-2016 at 08:20


Quote: Originally posted by Bender84  

@PHILOU
Quote:

Glycerol (propantriol) is normally more or equally expensive than glycol. What are your arguments in favor of a cheaper NG price vs EGDN one?

Glycerol is about 25% cheaper than glycol in EU mainly due to production of biodiesel. It is created during hydrolysis of fats and it is treated as waste in the process.

True that biodiesel has reduced the price of glycerol down to the price of ethylene glycol between 2003 and 2006.
Maybe that by now the price is lower...I have no datas about it.

But the price will not stay so because vegetable oils (triglycerides) that are used to make biodiesel will be in competition with its use as food... The EU wishes that biodiesel enters by 10% into the composition of car diesel by 2020 or so...but this is a wild dream because for example for the tiny country I live in what is Belgium, this would mean to make monoculture of oilish plants on all the Belgium land surface...and this is not possible, so it has to be done out of the EU in Africa and this would be a disaster for ecology and bio-diversity...but also not possible; so the only way is to take low price vegetable oils normaly used for the food...thus meaning an increase of both prices diesel and food!

Between low cost food and low cost biodiesel, the people will make a fast choice.

Quote: Originally posted by Bender84  

Quote:

If you make a mix of the two, you may think that by the colligative laws, you will reduce the volatility of the two compounds...unfortunately it only works if one of the component is a non volatile compound...so here by opposition you will have a slighly higher vapour pressure of the most volatile component above it...what changes nothing for security or safety.

Correct me if I’m wrong, but I think that you can treat NG/EGDN as an ideal mixture, therefore it is subject to Raoult’s Law. So, e.g. for 60:40 mix, the total vapor pressure of the mixture would be 0,0202 mbar (using the vapor pressure values given in Meyer's Explosives 6th ed.), and for the 70:30 mix it will be 0,0152 mbar. You get ~25% decrease in volatility if you increase the NG content by 10%.

The mix is not as ideal as you may think it is...because EGDN is a central symetrical molecule with a dipole moment close to 0 Debye while NG which is a mirror symetrical molecule displays a dipole moment of 3,82 Debye...so you mix something fully apolar with something moderately polar.

Your example is a good one but you only watch at what you want...
If indeed by using 60/40 and 70/30 mixes of NG/EGDN, you (hypothetically by using Raoults law for ideal mixes) reduce the volatility respectively of 59,604% and 69,538% vs EGDN; ab contrario you increase the volatility by 6121% and 4615% vs NG... you noticed it by writing in your last post "Increasing the content of EGDN is not an option due to the high volatility of the substance (risk of exceeding the TLV)."

Quote: Originally posted by Bender84  

Quote:

Also a more volatile compound in the mix will favor tiny bubbles formation inside it what is a call for disaster in the case of NG and EGDN due to the increased shock sensitivity.

I have never seen such phenomenon in my career, neither the people who work decades longer than me in the industry. In conditions we are using the mixture not such thing has ever happened.

It must be linked to the solubility of gases into NG and EGDN that must be different so saturated solution at STP when mixed will degas from the solvent that dissolves the more due to the solvent that dissolves less.
Owing to the very different dipole moment, one may expect very different solubilities.
The tiny bubbles will be enriched by the more volatile solvent --> EGDN.

Quote: Originally posted by Bender84  

And what about the freezing curve? Do you (or anyone who reads this topic) know where I can find such diagram?

About the freezing and vaporisation curve I'm working on it but I must admit that the fact NG displays two solid forms with two different MPs (labile NG=3°C and stable NG 13°C) is not easy.

Also I like the effort of Hennig Brand, but the Raoult's law for lowering of the MP is only valid if dilluted so close to the edges.
I'm checking the calcul spreadsheet of Hennig to understand it and see where problems my be...

dT = Kc * m
Where:
1°)Kc is the cryoscopic constant (lowering of mp in°C for 1 mole of undissociated solutant in 1 kg of solvant)
2°)m is the molality thus the number of moles (n) of undissociated solutant in 1 kg of solvant = n/kg

By definition n = mass of solutant/ MW solutant = m/M
dT = Kc * m = Kc * n/kg = Kc * (m/M)/kg

If n=1 --> m=M and dT = Kc

So the dependance between variation of T° and m (or n of solutant or m of solutant) should be linear with a slope of Kc but the graph of Hennig is not linear...



[Edited on 8-4-2016 by PHILOU Zrealone]




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[*] posted on 9-4-2016 at 08:30


Bender84, thank you for the kind words and thanks for providing the graph as well. Very interesting!

Yes, it looks as though the intermolecular forces between NG and EGDN are very different than between molecules of NG.
The amount of solvent is fixed, so the temperature drop does not change linearly with mass fraction / percentage NG or EGDN.
I will have another look at this in the next few days if I get a bit more time.




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[*] posted on 9-4-2016 at 11:47


Yes Hennig, you have used a mass fraction...
Usually Raoult's law for vapour pressure plays with X = the mole fraction.
For a binary system A and B...
Xa = na/ntotal = na/(na+nb)
By definition Xa + Xb = 1

Indeed when the solvent is in large excess vs solutant, then mass fraction, molar fraction, molality do display similar...

The main problem is that the effect of lowering of the melting point applies to both compounds here since they interact on each other...and this especially in the middle regio where the two compounds are 50/50.

This effect is used for a fast test in organic lab to be sure of the identification of a compound of known melting point.
If you have two solid compounds A and B with similar melting points, A is your reference compound and B is the one you want a verification of.
Then you put A, B and M (a A/B mix (50/50)) in 3 separate capillarity tubes and you put those in a metal heating block to check the simultaneous melting point/temperature of A, B and M.
If M melts at the same time as A and B; then A and B are identical;
but if M melts prior to A and B; then A is a different molecule than B.

[Edited on 9-4-2016 by PHILOU Zrealone]




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[*] posted on 9-4-2016 at 16:54



[Delta] = E(_m_/M)

where,
[Delta] = temperature change for 100g of solvent
m = mass of solute
M = molecular weight of solute
E = Constant (70.5 for NG)

or

dT = Kc * (m/M)/kg

Divide E = 70.5 by 10 to give Kc = 7.05 and we have the same equation, except now it measures temperature change for 1kg (1000g) of solvent not 100g anymore.

The first way above, from Nitro Explosives, is likely not conventional anymore, but I think it gives the same results.

I didn't intend for what I did to be the final word on NG/EGDN phase diagrams. I found a few bits of information on the internet, and got a start on it. Though probably very inaccurate, it was still a very worthwhile exercise because of what was learned/is being learned.


[Edited on 10-4-2016 by Hennig Brand]




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