Sciencemadness Discussion Board

Distillation of Hydrazine Hydrate in Glass Apparatus

Keith Fletcher - 7-12-2015 at 06:52

I created a solution of 15 grams of N2H4OH with the sulfate hydroxide method in 125ml of anhydrous Ethanol. I then put it into a 250ml round flask attached a 300mm fractionating column and a gram condenser. I switched to a Liebig once the Hydrazine fraction started to come over. I got 115ml of fraction that boiled at 72-78C at 1,175 feet above sea level. Then I got about 13 ml of fraction that boiled at 91-98c. and weighs 10.3 grams. I left the distilation over night (12 hours) so the temp could have rose higher than 98. The temp outside was 19C. The glass apparatus is fine with no sighs of corrosion. I wafted the 92-98C fraction and the oder is like 30% NH4OH so I think I have isolated the Hydrazine-OH. I think I will distill it again since the fraction that came over is somewhat cloudy. I will make a YouTube video with more details. I tried for hours to find out the Ethanol Hydrazine-OH azeotrope but to no avail I then tried to calculate it but I could not, so I guess I'm a shit chemist in that aspect. I will now proclaim that Hydrazine forms an azeotrope with Ethanol with a density of 1.26g/ml and boils between 92-98C. Please corect any mistakes and share your hydrazine distillation experiences I stood behind one inch of acrylic for 4 hours watching this thing outside in 19C weather so please input into this
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[Edited on 7-12-2015 by Keith Fletcher]

Deathunter88 - 7-12-2015 at 08:20

I can't really comment on the hydrazine distillation itself, but you really shouldn't use graham condensers horizontally. They are meant to be used vertically in order to prevent pressure buildup.

Keith Fletcher - 7-12-2015 at 08:30

yeah, im sorry about the im proper use of the Graham condenser. I have herd of problems with it but i have used it like this for the past year at least 20+ distillations and no problems. No burst joints or sudden apparatus separations. The pressure from the boiling distillate forces the liquid through the loop. I don't keep the apparatus sealed but leave the vacuum port open to prevent pressure from building up. I like the gram because of the increased surface area, but if you persist in your concerns I will stop using it in this way. :)

hissingnoise - 7-12-2015 at 08:39

The pressure from the boiling distillate forces the liquid through the loop.

Any pooling in the coil significantly reduces efficiency . . .

Keith Fletcher - 7-12-2015 at 08:40

not that i saw

hissingnoise - 7-12-2015 at 09:03

Just do as you're told, OK? :D

Magpie - 7-12-2015 at 09:04

I can't add much to help you as I've never made any of this beyond about a 3% concentration, which I used to make a precursor for luminol. It worked well.

Hydrazine is NH2-NH2; the hydrate would be NH2-NH2*xH2O.

I plan to make concentrated hydrazine hydrate sometime in the future. That is why I fabricated a copper RBF.

For a complete list of azeotropes see Jurgen Gmehling et al's Azeotropic Data.

aga - 7-12-2015 at 11:35

Quote: Originally posted by Keith Fletcher  
not that i saw

Without doing a series of quantitative comparative tests with different types of condenser, or even the same condenser at different angles, you wouldn't be Able to see if it did or not ...

That's wot they call Science !

Keith Fletcher - 7-12-2015 at 12:35

Good point aga, I might make a YouTube video about that in the future. I have never had a problem with my Graham horizontal. The vapor just seemed to collect in the coils and and eventually fill the condenser and the vapor pressure pushes it into the collection flask.

I am tired, aga suggest a seres of tests an I shall carry them out once the hangover is gone. I will post a video.

I am taking my dog for a walk so I wont respond for like an hour or two.

[Edited on 7-12-2015 by Keith Fletcher]

BromicAcid - 8-12-2015 at 04:43

With the 'sulfate hydroxide method' do you mean using barium hydroxide to crash out the sulfate and filtering? I'd like to see more details for your sulfate method, which reagents were in excess, did everything dissolve well, etc. You may have introduced additional water based on the chemistries.

As far as I remember, the main reason hydrazine hydrate is not distilled in glass is due to the risk of explosion. This can be brought on by the surface of the ground glass acting to catalytically promote the breakdown of hydrazine hydrate to its elements. A lot of the older references for making hydrazine hydrate and anhydrous hydrazine utilize lots of KOH or NaOH along with solid hydrazine sulfate in a silver retort. In this case you need a silver retort since the high temperatures and solid hydroxides would not be good for the health of your glassware. I have seen from sever sources that hydrazine is corrosive to glassware, however other literature sources say that is is not. I have to wonder if some of this is the propagation of misinformation based on the initial reaction involving using that boat load of hydroxide.

N2H4OH is just wrong, it looks like you have some sort of hydroxyl amine. Hydrazine hydrate is N<sub>2</sub>H<sub>4</sub>*H<sub>2</sub>O, you're missing a proton in your formula.

The backpressure generated by a Graham condenser is usually pretty trivial, it just doesn't look 'clean' and wouldn't be proper technique. However aside from that it is fine, it is much better than winding tubing through a soft drink bottle and filling with ice, that's for sure.

What really hits a red flag though was your distillation, you really shouldn't be leaving your setup alone distilling for 12 hours, especially with hydrazine. What was your heat source, was it something that was self-limiting like a hot water bath?

chemrox - 8-12-2015 at 13:24

Thanks Bromic. " I'd like to see more details for your sulfate method, which reagents were in excess, did everything dissolve well, etc. You may have introduced additional water based on the chemistries." Me too. Fractionating with what column. Short Vigeraux columns won't get you to a crisp bp as you found out. I would use a Snyder or better yet a packed column with a controllable (partial take-off) reflux head.

Keith Fletcher - 8-12-2015 at 14:26

I used a 10$ electric camping stove to heat it and I used one of my 250ml round bottoms that already had a crack that did not leak, because there was an significant risk of an explosion and I didn't want to risk a good round bottom.I did use my 300mm fractionating column and i was woried about it being damaged. I didn't use an oil bath because if it did explode it would eject boiling oil every were and catch fire. I could not use a water bath because I read that Hydrazine Hydrate boils at 120C so I just warped the flask and the column in foil to increase the temperature it was 19C outside so it was difficult to keep it hot after the first fraction came over. I should have used a sand bath. I'm stupid sorry about the N2H4OH error N2H4-H2O I'm very sorry about that.

I took 61.6 grams of Hydrazine Sulfate(that was all I had) Then I added it to 39 grams of Sodium Hydroxide and 150ml of Ethanol and swirled the glass until it was homogeneous but nether chemical dissolved. The mixture began to heat up on its own so I attached a graham condenser and allowed the reaction to cool down. Sodium sulfate had formed and was not crystalline but somewhat plastic it was strange I tried to vacuum filter it but it was too plastic (Silly putty plastic) so i had to decant I then mixed the Sodium Sulfate plastic with hot water and dissolved it. Then i took the 130-140ml EtOH and Hydrazine Hydrate solution and distiled it. The fact that i left it over night was negligent on my part and I apologize for that. The fraction was coming over so slow that I knew it would take hours for it to complete. I kinda thought that since it didn't explode within the first five hours of distillation that It just wasn't, but again it was negligent of me to do that.

I slept with a fire extinguisher next to my bed and I'm glad I didn't have to use it. :)

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improper use of a graham condenser :)

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Glass was cracked before distillation, you can see a little bit of corrosion but its was not as significant as I thought would occur.

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better setup

[Edited on 8-12-2015 by Keith Fletcher]

gdflp - 8-12-2015 at 15:01

Is that the boiling flask which is cracked?!? Even if it still holds liquid, a crack in the flask, especially one that large, compromises both the structural and thermal integrity of the flask, and the flask shouldn't be used. It's not just a cosmetic defect!

Keith Fletcher - 8-12-2015 at 15:16

yes, I think I will not use it any more. I was expecting it to be exploded:D