Sciencemadness Discussion Board
Not logged in [Login - Register]
Go To Bottom

Printable Version  
 Pages:  1  
Author: Subject: Preparation of Hydrazine Sulfate (Hofmann Degradation)
Magpie
lab constructor
*****




Posts: 5341
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 17-12-2010 at 20:04
Preparation of Hydrazine Sulfate (Hofmann Degradation)


Preparation of Hydrazine Sulfate (Rosco Bodine)

paraphrased by Magpie

12/19/10



This is a scaled down (18.7%) version of the improved procedure posted by Mr Anonymous (Rosco Bodine) on SM on 6/7/03. Some improvements by garage chemist (SM post on 5/19/07) were also incorporated.


A. Reagents

355 mL of 10wt% NaOCl solution (0.55 mole)
47.8g of NaOH (1.20 mole)
34.1g of urea (0.57 mole)
0.47g gelatine
122 mL of 31% HCl (1.18 mole)
37.5mL of conc (92%) H2SO4 (0.64 mole)
30mL of 70% isopropyl alcohol
15mL of anhydrous isopropyl alcohol
water



B. Equipment
fume hood
1 quart jar with threaded lid
1-liter mL Erlenmeyer flask
250 mL pressure-equalizing (P-E) dropping funnel
24/40 to 19/22 reducing adaptor
24/40 Keck clamp
#9 rubber stopper with ½” dia hole
2 quart plastic funnel
plastic plate to cover mouth of funnel
magnetic stirrer/hotplate
3” magnetic stir bar
15cm Buchner funnel with filter paper
fridge for cooling to at least 8ºC (46ºF)
freezer
thermometer
small watch glass for the 1-liter E. flask
small watch glass for P-E dropping funnel fill port
bowl for use as a cooling pan for the 1-liter E. flask
ceramic dinner plate
ringstand with clamp for P-E dropping funnel
25mL beaker
250mL beaker
stirring rod
125mL Erlenmeyer flask w/stopper
250mL Erlenmeyer flask w/stopper




C. Cautions
1. Hydrazine is highly toxic.
2. Hydrazine is an environmental hazard.
3. Hydrazine is flammable.
4. Hydrazine is destroyed by air.

D. Procedure

a. Prepare the Cold NaOCl/NaOH Solution
1. Place 355mL of 10% NaOCl solution in a 1-quart jar with screw cap and cool to at least 8°C (46°F) in a fridge (or freezer).
2. Using a magnetic stirrer mix in NaOH to the cooled NaOCl solution in two 23.9g portions, cooling in between to 8°C. Try not to let the temperature rise above 20°C. Then chill in the fridge to 5-8°C.

b. Prepare the Urea/Gelatine Solution
1. Place 3mL of water in a 25mL beaker. Sprinkle in the 0.47g of gelatine, breaking it up and dispersing it with a stirring rod. Add 15mL of boiling water and stir the gelatine until dissolved.
2. Add 20mL of hot water to a 250mL beaker. Then add 34.1g of urea and stir until dissolved.
3. Pour the gelatine solution into the urea solution and stir until mixed.

c. Form the Hydrazine Solution
This is to be done in the hood as hydrazine is toxic.

(H2N)2C=O + NaOCl + 2 NaOH → N2H4 + H2O + NaCl + Na2CO3
(Hofmann degradation)

Note: A viscous, voluminous foam will be quickly formed in the following reaction. Vigorous action by the large magnetic stir bar will help keep it beaten down.

1. Place the 3” stir bar in the 1-liter E. flask and place on the magnetic stirrer/hotplate.
Insert the plastic funnel in the one-hole stopper.

Note: The following reaction should be allowed to take place for a few minutes before supplemental heating is applied. As the foam begins to dissipate heat is to be applied to steadily drive the reaction to completion at boiling.

2. Retrieve the hypochlorite solution from the freezer.

3. When the hypochlorite solution has warmed to 5-8°C, set the stir bar at speed 3 and pour the hypochlorite solution into the E. flask. Install the plastic funnel w/stopper in the E. flask. Then quickly pour in the urea/gelatine solution through the funnel into the vortex. Immediately raise the stir bar speed as required.

4. Cover the funnel with a plastic plate. The reaction initiates immediately and a snow white foam will rise to fill the flask to about the 900mL level, but possibly may even overflow into the funnel. After a few minutes the foam will begin to subside and the solution will turn translucent orange, and heat up. Turn down the stir rate to prevent foam generation. Apply heat steadily to drive the solution to boiling. The color will fade to a pale yellow then to almost clear. The clear color indicates the endpoint of the reaction. At this point heating is stopped.

5. Remove the overflow funnel and place a small watch glass over the mouth of the flask to exclude air. The watch glass will allow any CO2 to escape and also prevent a vacuum from forming. Cool the flask well in an ice bath. This is in preparation for the neutralization, during which an exotherm will be generated.

d. Neutralization with HCl
This should be done in the hood as considerable CO2 is released.

2HCl + Na2CO3 --> 2NaCl + CO2 + H2O + heat

1. While the reaction mixture is cooling measure out 122 mL of 31% HCl into a 250 mL E. flask, stopper, and place in the freezer to cool.

2. Prepare a diluted sulfuric acid solution of 38mLs of conc sulfuric acid diluted with 33 mLs of water in a 125mL E. flask. Stopper and place in the freezer to prepare for the formation of the hydrazine sulfate.

3. Attach a 24/40 to 19/22 adaptor to a 250 mL pressure-equalizing dropping funnel using a Keck clamp. Insert the outlet of the adaptor into the #9 one-holed stopper. Support the addition funnel with a ringstand and clamp and insert the stopper in the 1-liter E. flask. Add the cooled HCl from the freezer to the P-E dropping funnel (valve closed!). Place a small watch glass over the fill port of the P-E dropping funnel. This excludes air, which destroys hydrazine, yet allows the CO2 to escape as the HCl is being added. Add the HCl at 1 drop/sec to the hydrazine solution stirred on the stirrer/hotplate. The mixture will warm up.

e. Formation of Hydrazine Sulfate
NH2-NH2 + H2SO4 --> [N2H5]HSO4

1. Close the valve on the P-E dropping funnel and add the cooled/diluted sulfuric acid.
2. To the rapidly stirring mixture add the dilute sulfuric acid at 2 drops/sec. Reduce the drip rate to control foaming if necessary.
3. Continue stirring and slow the drip rate to about 1 drop/sec as crystals of hydrazine sulfate begin to appear. Stir for one hour past the addition point.
4. Place a small watch glass on the mouth of the E. flask and set aside in a cool place overnight. CO2 may continue to vent.
5. Just prior to filtering the crystals cool the flask in an ice bath for at least an hour.


f. Filtering the Crystals
1. Set up the 15cm Buchner funnel with filter paper for vacuum filtration.
2. Stir the E. flask to loosen any CO2 bubbles and clumps of crystals.
3. Remove the stir bar from the flask.
4. Decant the supernate and save it for washing crystals out of the flask.
5. Pour the crystal slurry onto the Buchner funnel and suck the supernate from the crystals.
6. Flood the wet but drained crystals with 30 mL of 70% isopropyl alcohol, stirring with a stirring rod.
7. Use a final rinse of 15 mL of anhydrous isopropyl alcohol
8. Remove the filter paper with crystals and wick away any excess liquid on a blotter paper or paper towels.
9. Air dry the crystals on a dinner plate.


E. Expected Yield
The expected yield for Mr. A’s full scale batch is about 60% based on the amount of hypochlorite used. For this reduced scale that would be 41 to 44g (0.33 mole). MP of hydrazine sulfate is 254 °C per the Baker MSDS.

F. References

1. Improved procedure of Mr. Anonymous, posted on SM 6/7/2003.
2. SM post of garage chemist on 5/19/07 providing an improvement and a reduced scale.
3. Merck patent GB392845, upon which Mr. A’s procedure is based.
4. Wikipedia entries for “hydrazine” and “Hofmann degradation.”


reagents for hydrazine.JPG - 39kB hydrazine rx near endpoint.JPG - 36kB neutralization using HCl.JPG - 35kB

[Edited on 18-12-2010 by Magpie]

[Edited on 18-12-2010 by Magpie]

[file]12386[/file] [file]12388[/file] [file]12390[/file]

[Edited on 18-12-2010 by Magpie]

[Edited on 18-12-2010 by Magpie]

[Edited on 20-12-2010 by Magpie]




The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5341
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 17-12-2010 at 20:10


I felt that a scaled down version of Rosco's fine procedure would be useful to many home chemists who only want to make ~30g of hydrazine sulfate. I worked with Rosco to prepare a procedure that was mutually acceptable. We hope you find it useful.



The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
chemoleo
Biochemicus Energeticus
*******




Posts: 3005
Registered: 23-7-2003
Location: England Germany
Member Is Offline

Mood: crystalline

[*] posted on 18-12-2010 at 17:41


Hi Magpie, what was your yield of Hydrazine sulfate at this reduced scale?
I have always had the impression that yields generally are terrible.... certainly my own attempts years ago yielded a few grams at best.
Did you perform any test on the final product to ascertain that it really is hydrazine sulfate? (silver mirror etc)?




Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5341
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 18-12-2010 at 18:35


Quote: Originally posted by chemoleo  
Hi Magpie, what was your yield of Hydrazine sulfate at this reduced scale?
I have always had the impression that yields generally are terrible.... certainly my own attempts years ago yielded a few grams at best.
Did you perform any test on the final product to ascertain that it really is hydrazine sulfate? (silver mirror etc)?


Hi chemoleo. I have done this synthesis twice. The first time my yield was 31g, or 53%. That was back in May. I used some of it to make 3% hydrazine, which in turn, was used to make luminol, which was quite succesful.

I did the second synthesis a few days ago as I'm gearing up to make semicarbazide. The yield here was lower at 17.8g, or 30.4%. But I blame this on the fact that I forgot step e.5, where the hydrazine sulfate liquor is cooled in an ice bath for at least an hour prior to filtering.




The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
Rosco Bodine
International Hazard
*****




Posts: 6093
Registered: 29-9-2004
Member Is Offline

Mood: analytical

[*] posted on 18-12-2010 at 23:57


@Magpie I may have found a computational error you should look at here.

I am checking your reaction quantities and your figures are not a direct scaledown gotten by simply adjusting the procedure quantities by using a
.187 multiplier. Without checking the solution densities to adjust for the small difference more closely, just based upon your use of 12.5% versus the 10% NaOCl, 80% of the multiplier scaled volume for 10% would be the approximate adjustment
for using the 12.5%. .187 X 1892 ml = 353.8 ml ( X .8 ) = 283 ml
However you are showing 222 ml of the 12.5% NaOCl
The missing 61 ml of 12.5% NaOCl will likely diminish the expected yield significantly. Adjusting this quantity to
a larger value closer to 283 ml should put your yield
well over 60% ( 40+ grams )

And for the NaOH .187 X 255 g = 47.7 g However you are showing 45 g NaOH probably not significant

And for the urea .187 X 182 g = 34 g

And for gelatine .187 X 2.5 g = .47 g



[Edited on 19-12-2010 by Rosco Bodine]
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5341
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 19-12-2010 at 08:42


I,m checking my basis and calculations now & will reply soon.



The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
Bolt
Hazard to Others
***




Posts: 188
Registered: 26-3-2007
Member Is Offline


[*] posted on 19-12-2010 at 08:49


Hi, would you please include an explanation of why the gelatin was used?
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5341
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 19-12-2010 at 10:09


Quote: Originally posted by Bolt  
Hi, would you please include an explanation of why the gelatin was used?


Rosco, please correct me if I'm wrong, but I believe the gelatine is there to absorb heavy metals such as iron, copper, and nickel, as they will cause decomposition of NaOCl.

Here's a site with more information than you'll likely want:

http://www.omegachem.com.au/docs/mega_handbook.pdf




The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
Rosco Bodine
International Hazard
*****




Posts: 6093
Registered: 29-9-2004
Member Is Offline

Mood: analytical

[*] posted on 19-12-2010 at 10:41


That is part of how the gelatin is involved but there is more that it does too as an actual component of the reaction forming the hydrazine ....I think. It has been
years since I was researching this so I can't be specific on exactly what is the
mechanism there, but I know they tried substitution of chelating agents and viscosity increasing substitutes which failed to work in the same way as does gelatin. The explanation was that somehow the gelatin participates as an
active reactant and is not just a spectator or inert component in the hydrazine formation.
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5341
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 19-12-2010 at 11:38



@Rosco
I finally found garage chemist's post with his "Improvement" so I can now get to the matter of the discrepancies you pointed out.

But, I have a question for you first: What is the gas that is generating all that foam during the formation of hydrazine. I think you mentioned in a U2U that it was CO2. But there is none generated in the Hofmann degradation reaction. In my reading through some of the 15 page hydrazine thread GC mentions that degradation to N2 is surely a side reaction when NaOCl reacts with urea. This seems more likely to me based on observation. What do you think?




The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
Rosco Bodine
International Hazard
*****




Posts: 6093
Registered: 29-9-2004
Member Is Offline

Mood: analytical

[*] posted on 19-12-2010 at 12:42


The Schestakow reaction looks the same in reviewing it now,
so CO2 seems to be the byproduct there.

http://www.sciencemadness.org/talk/viewthread.php?tid=1128&g...

I should reiterate that the conditions for preferential hydrazine formation
are highly specific due to competing reactions that are going to proceed more
favorably if the narrow window conditions which I described are not reproduced
with good precision. You cannot stray very far from the straight and narrow path
on this fickle synthesis and still get good yields.

http://www.youtube.com/watch?v=X5_2_A6R3vU&feature=related

http://www.youtube.com/watch?v=5zQmVgvHVvw&NR=1

http://www.youtube.com/watch?v=3uQxYljNDL0&feature=related

[Edited on 19-12-2010 by Rosco Bodine]
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5341
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 19-12-2010 at 13:28


Quote: Originally posted by Rosco Bodine  
The Schestakow reaction looks the same in reviewing it now,
so CO2 seems to be the byproduct there.


@Rosco
Thank you. This is a very interesting subject.

I have resurrected my numbers and now see where I got them. I basically just used the numbers that GC had for his reduced scale batch as he posted in his "Improvement" on 5/19/07 in the "Hydrazine" thread, p.8, since he said he had "great success." Here his basis is 0.45 mole of NaOCl and 34.1g of urea,

I used nominal 12.5% NaOCl, HASACLOR, which is sold for use in swimming pools. HASA's MSDS states a density of 1.20, so for 0.45mole:

(V, mL)(1.20g/mL)(0.125)/(74.44g/g-mole) = 0.45 g-mole

V = 220mL

The rest of the numbers are straight out of GC's post.

Before I did the preparation I titrated the HASACHLOR with standardized thiosulfate and found the actual concentration to be 12.2%. So, in practice, I compensate the volume used to get the full 0.45 mole.

So, if you feel that 0.45 mole of NaOCl is not quite enough for this synthesis, please suggest a corrected amount. This is true for any of the other reagents. They all can be tweaked if you think they should be. Just let me know.

[Edited on 19-12-2010 by Magpie]




The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
Rosco Bodine
International Hazard
*****




Posts: 6093
Registered: 29-9-2004
Member Is Offline

Mood: analytical

[*] posted on 19-12-2010 at 13:49


I wouldn't trust an MSDS but use a volumetric weight to calculate density, and use a chart to keep 'em honest.
It should come out at least 1.210 sp.g. for 12.5% NaOCl
You can interpolate the non charted values close enough.
Really you should match mole for mole what I published
as the optimized result from variations on 6 experiments.
I don't still have the worksheets showing the plots to the
optimum conditions......so you will just have to trust me :D

GC's numbers, temps, ect. are GC's and not mine.

Use the straight multiplier .187 right down the line for
mole equivalents and disregard the H2O difference.
You don't want excess urea leftover unreacted for a deficiency of hypochlorite because it will further react
with the hydrazine that has been formed. I tuned and
tweaked those numbers right and double checked it,
and what I got is exactly what I wrote.


Attachment: bleach.pdf (80kB)
This file has been downloaded 1034 times

[Edited on 19-12-2010 by Rosco Bodine]
View user's profile View All Posts By User
garage chemist
chemical wizard
*****




Posts: 1805
Registered: 16-8-2004
Location: Germany
Member Is Offline


[*] posted on 19-12-2010 at 13:50


Nice work. The gas that produces the foam is N2 due to a side reaction. CO2 cannot be generated since the mixture is highly alkaline during the reaction. The CO2 stays bound as carbonate in the solution and is released during the acidification.

Chemoleo, in my first few tries with this reaction I also got very little or zero yield, and massive foaming, instantly overflowing the flask and making a huge mess. I then found that my NaOCl solution was significantly stronger than the required 12,5%. NaOCl instantly oxidises hydrazine to N2, accounting for the extreme foaming, and any excess of NaOCl has to be strictly avoided. Since aqueous NaOCl slowly decomposes during storage, and you never know the exact concentration, I started making my own 10% NaOCl from chilled, excess aqueous NaOH and chlorine from a gas generator charged with a carefully calculated, weighed and powdered amount of TCCA.
The NaOCl could not easily be made stronger than 10% since otherwise NaCl would precipitate (its solubility in aqueous NaOH is low) and coat the chlorine bubbles as a gelatinous film, severely slowing down absorption.
Using fresh selfmade NaOCl of known concentration, I consistently got good yields.
I also changed the stochiometry of reactants according to my own ideas about the reaction (excess of urea and further excess of NaOH, and not using Roscos amounts), which further improved yields.

Magpie, can you link to my post in which I described an improvement? I can't find the one you're meaning.




www.versuchschemie.de
Das aktivste deutsche Chemieforum!
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5341
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 19-12-2010 at 14:03


Quote: Originally posted by garage chemist  

Magpie, can you link to my post in which I described an improvement? I can't find the one you're meaning.


Yes, here: http://www.sciencemadness.org/talk/viewthread.php?tid=1128&p...




The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
garage chemist
chemical wizard
*****




Posts: 1805
Registered: 16-8-2004
Location: Germany
Member Is Offline


[*] posted on 19-12-2010 at 14:28


Ah, you mean the preparation of NaOCl solution from calcium hypochlorite! Yes that works very well if done correctly, and allows the preparation of fresh 15% NaOCl solution without hassle or chlorine gas.
Do you want to try this too?




www.versuchschemie.de
Das aktivste deutsche Chemieforum!
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5341
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 19-12-2010 at 14:43


Yes, you make your own NaOCl. The "Improvement" is in the 3rd post from the bottom of the page. Here:


Quote:

The yields of the chlorourea batches were terrible, totally useless. First one gave ca. 15g, second one maybe 5g. I abandoned the chlorourea method for me, primarily because the chlorourea is unstable and a huge excess of urea over chlorine has to be used, among other reasons. ------------------------------- Today I have prepared the first batch of hydrazine sulfate using 70% Calcium hypochlorite (HTH pool chlorine) as the hypochlorite source. I used 51,1g HTH, which I reacted with 37,8g Na2CO3, both as solutions, in the way I described in this thread: http://www.sciencemadness.org/talk/viewthread.php?tid=8504 190ml of 15% NaOCl were obtained, corresponding to 0,45mol of NaOCl, a 90% yield in regard to HTH. The rest of the synthesis was analogous to Mr. Anonymous' method for hydrazine sulfate, with some changes implemented by me. I noticed that the solid NaOH dissolved extremely slowly in the 15% NaOCl when it was cold, and only started to dissolve with any noticeable speed as the temperature went above 10°C. But then the temperature did not rise above 20°C after the portion of NaOH had dissolved, so there was no problem. I added the NaOH in two portions of 22,5g each (with cooling between additions to 8°C), for a total of 45g NaOH with the 0,45 mol NaOCl. The Improvement: The 15% NaOCl was not chilled in the freezer, the fridge with 8°C did perfectly fine. With the NaOH added in two portions, the temperature will not go above 20°C. The same goes for the original HS synthesis when 10% NaOCl pool chlorinator is used! If the NaOCl is chilled in the freezer instead of the fridge, the NaOCl will simply warm up by itself to 10°C before the NaOH starts to dissolve. So not cooling below 0°C makes the process both easier and faster. The NaOH stabilizes the NaOCl, so that 20°C can be tolerated for a short period of time if the NaOCl is chilled immediately after again. After all NaOH had been dissolved, the NaOCl was chilled in the freezer to below 0°C, urea (34,1g) and gelatin (0,56g) were dissolved together in 40ml warm water and the instructions of Mr. Anonymous were followed until the end. The foam rose to 1000ml from the ca. 250ml of solution. The reaction became extremely hot by itself after the foam was produced. It subsided again quickly after. Slowly heated to boiling until colorless, cooled, neutralized with 120ml 31% HCl and precipitated with 34ml conc H2SO4 (previously diluted with its own volume of water). The batch is currently cooling. A lot of HS was already precipitating after the H2SO4 had been added, despite the solution still being hot. I heated until all had been dissolved, and then slowly left it cool in order to produce larger crystals. This works extremely well, as I can already see. [Edited on 19-5-2007 by garage chemist]


Actually, I was happy with the use of the swimming pool NaOCl as I got 53% yield on the first batch. Over the summer the NaOCl concentration has dropped to 10.5% and then I forgot to ice cool the crystals just before filtering, so the second batch was not so good at 30.4%. It's also cold in my garage lab, even with the heater on.




The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
Rosco Bodine
International Hazard
*****




Posts: 6093
Registered: 29-9-2004
Member Is Offline

Mood: analytical

[*] posted on 19-12-2010 at 15:00


Nicodem provided some information concerning the Schestakow reaction
which may provide further insight if the references are examined

http://www.sciencemadness.org/talk/viewthread.php?tid=1128&g...
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5341
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 19-12-2010 at 17:51


Quote: Originally posted by Rosco Bodine  


GC's numbers, temps, ect. are GC's and not mine.

Use the straight multiplier .187 right down the line for
mole equivalents and disregard the H2O difference.
You don't want excess urea leftover unreacted for a deficiency of hypochlorite because it will further react
with the hydrazine that has been formed. I tuned and
tweaked those numbers right and double checked it,
and what I got is exactly what I wrote.


@Rosco
You are right. I have revised the procedure. I changed the gelatine dissolution to be in line with you and Knox. Take a look and give me any comments you have.




The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
Rosco Bodine
International Hazard
*****




Posts: 6093
Registered: 29-9-2004
Member Is Offline

Mood: analytical

[*] posted on 19-12-2010 at 21:45


That looks better. Here's what should be recognized. It is a narrow window
and fickle reaction that is like a key matched to a lock using 10% hypochlorite.
Change to 12.5% could change other values that worked great for 10%, and
for 15% it could be yet a third set of optimum numbers. But the numbers probably won't vary a lot as molar ratios for the change in water content. What I would expect is for the induction temperature to drop for the more concentrated hypochlorite, and be higher for the more dilute, as a typical mass reaction effect.
I haven't scaled it up or down from what I was doing so I can't be certain what will change for scale. That was years ago that procedure was worked up, so it is a long way from fresh on my mind now. But I was definitely aware of the side reactions and watching the variables effect on the yield. The byproduct gases I didn't capture and analyze for clues about identifying reactions accounting for the missing 40% yield. There probably is some nitrogen in that gas from a known possible side reaction but I think most of it is probably CO2. It was my guess that the nascent CO2 was simply coming out at such a high rate as to overwhelm absorption by the NaOH. It would be easy enough to find out for sure. Test an aliquot for CO2 volume produced on neutralization. My focus was simply on getting the best yield of the hydrazine sulfate from the 10% pool hypochlorite, not mapping the involved reactions or byproduct reactions ....even though it is of course interesting what else is going on there.

Commercial 10% (trade per cent) when fresh should actually be 10.5% analysis
so the reality about the molar amount is closer to this range:
355 ml of 10% 1.163 = 412.865 g X .105 = 43.35 43.35 / 74.44 = 0.582 moles
on storage after bottling a decrease to actual 10% nominal gives 0.554 moles

for urea 34 g = 0.566 moles

muriatic 31.45% 20 deg. Baume d 1.1586 is ~10 moles / liter
100.06 ml = 1 mole HCl 122 ml = 1.22 moles

( excess is for manufacturers NaOH already in the NaOCl )

[Edited on 20-12-2010 by Rosco Bodine]
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5341
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 5-1-2011 at 14:21


Today I made a batch (32.7g) of hydrazine sulfate using this scaled down procedure. My pool NaOCl solution which tested 12.2% NaOCl back in May now tested 6.9% due to storage outside in a shed since that time.

I compensated for this by using enough of the solution to get the 0.55 mole specified. It is interesting to note that even though the NaOCl content had dropped significantly, the sp gr stayed the same at 1.195 as measured with a 100mL volumetric flask.

There was a lot of extra volume as water in this preparation. So, for the first time, I did get about 200mL of foam overflow into the funnel. Also all this dilution no doubt caused some loss of yield during the recovery of the crystals at the Buchner funnel. The %yield is still a respectable 45.7% based on the hypochlorite used.




The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
Mailinmypocket
International Hazard
*****




Posts: 1340
Registered: 12-5-2011
Member Is Offline


[*] posted on 16-7-2012 at 09:42


After much frustration due to foaming issues I found a synthesis for hydrazine sulfate in SM member len1's book which uses EDTA instead of gelatin. I scaled down the preparation to 1/3 of the original size and obtained an excellent yield! Best of all, little to no foaming at all!!


The book can be found in the following post by solo:

http://www.sciencemadness.org/talk/viewthread.php?tid=4388&p...

View user's profile View All Posts By User
nitro-genes
International Hazard
*****




Posts: 774
Registered: 5-4-2005
Member Is Offline


[*] posted on 10-7-2014 at 13:08


Thanks magpie for the write up, I largely used the quantities from your synthesis, only starting from calcium hypochlorite for the lazy ass, sunday morning, hobbiest like myself! :D

At first I was under the impression that an aquous solution of calcium hypochlorite would not be feasable for urea degradation, then I read patent EP 0115076 A1 which uses an aquous solution of Ca(ClO)2 to ammonia together with acetone to produce the azine. At first I experimented with pure Ca(ClO)2 + NaOH, but this produces a lot of foaming, probably beacause part of the calcium is precipitatated upon addition of NaOH. I also tried the Ca(ClO)2 + Na2CO3 to leave a NaClO solution after filtering, but the problem is that even when finely ground, the Ca(ClO)2 only partly dissolves due to low solubility (21 g/l) and the precipitate still produces a lot of chlorine upon acidification, which resulted in lowered and unpredictable yields. I'm sure this is not due to impurities, since todays Ca(ClO)2, is pretty pure and the package says 99%.

Still wanting to start direclty from Ca(ClO)2 I combined the two appraoches and just leave the solid CaCO3 precipitate present during the reaction, I figured that the azine after MEK addition would still separate:

36 grams of Ca(ClO)2 was finely powdered and added to 200 ml of destilled water (25 deg C) under fast stirring for 15 minutes. A solution of 72 grams of Na2(CO3)*10 H20 in a total of ~100 ml was made by heating untill all had dissolved. After cooling the soda solution to room temp, this was added while stirring to the Ca(ClO)2 solution. At this point some momentarily manual stirring is nessescary untill after 1 minute or so, the stirrer bar can handle things again. (At this point I largely followed your writeup). To this was added 53 grams of NaOH in small portions while cooling in a cold waterbath. (IIRC, temp control is not that important, since the NaOH stabilizes the ClO solution) The milk like suspension of hypochlorite-carbonate was added to the urea at once, heating was applied after half an hour and was allowed to rise to 90 deg C. over the course of one hour (under reflux) after which it was left to cool down to 40 deg C. again. 100 ml of MEK was added and stirred for an additional 1.5 hours.

The azine had no problems in separating cleanly, yield after H2SO4 treatmet needs to be determined (its in the freezer now) but looks promising. :) After many failed attempts using supermarket bleach (of unknown age), I think the calcium hypochlorite method may be a real advantage due to the fast decomposition of NaClO solutions. The calcium hypochlorite used was over 2 years old, and still seems pretty potent.

[Edited on 10-7-2014 by nitro-genes]
View user's profile View All Posts By User
nitro-genes
International Hazard
*****




Posts: 774
Registered: 5-4-2005
Member Is Offline


[*] posted on 16-7-2014 at 15:40


After a bit of reading I actually noticed the calcium hypochlorite method was allready here on the forum... Anyway after some additional experimentation, some things to add of (hopefully) additional value:

After some more experimentation, 15 minutes of stirring is not enough to allow all Ca(ClO)2 to dissolve/react with water, only after more than a hour of rapid (1250 rpm, RT) stirring, most of the Ca(ClO)2 has dissolved, and a fine precipitate of Ca(OH)2 remains at the bottom that (after washing) has very little residual ClO.

Also tried another method for producing really high % NaClO solutions by first adding NaOH in water (2 moles for every mole of Ca(ClO)2) and after cooling to room temperature, stirr in 1 mole equivalent of Ca(ClO)2 at high speed for 1 hour. A 20% solution was made this way, which was incredibly reactive (instant overflow).
View user's profile View All Posts By User
Hawkguy
National Hazard
****




Posts: 328
Registered: 10-10-2014
Location: British Columbia (Canada eh!)
Member Is Offline

Mood: Body is Ready

[*] posted on 26-4-2015 at 19:35


Okay so after doing this a few times, I noticed that the yields are low, as warned. Is it possible to distill Hydrazine out of the solution (After boiling off water) after the neutralization with Hydrochloric Acid? Or will Hydrazine Hydrochlorides have been formed after the HCl addition, making it difficult to distill?
View user's profile View All Posts By User
 Pages:  1  

  Go To Top