Sciencemadness Discussion Board

Making Hydrazine

Hexavalent - 18-2-2012 at 08:03

I understand that liquid Hydrazine can be prepared by the dry distillation of Hydrazine Sulfate and a base (namely NaOH), all done under inert atmosphere conditions. Can anyone enlighten me on the balanced equation for this reaction?

N2H4-H2SO4 + NaOH ----> N2H4 + ??

[Edited on 18-2-2012 by Hexavalent]

smaerd - 18-2-2012 at 09:16

This should definitely be in beginnings, think acid base reaction, and incredibly dangerous. Hydrazine is a weak base, hence the salt formation with H2SO4(generally considered a strong acid) at it's first ionization level. This ends up making a conjugate acid and a conjugate base(probably bad elocution there). Sodium hydroxide being a strong base. When you get to general chemistry this will be drilled into your head "An acid plus a base forms a salt and water". Acid Base Equilibrium is an important topic in chemistry from buffers to reactions themselves, I highly suggest reading up on it.

I think I remember reading that you are 13 years old somewhere on the forum. This is chemistry I wouldn't even consider touching and I'm almost twice your age and probably have a few more years experience in the lab. I'm pretty sure you also need a copper flask. Not trying to talk down on you but rather influence you into not thinking about performing this. I

Hexavalent - 18-2-2012 at 10:08

I am aware that an acid and a base creates a salt and water. I was just curious as to whether the sulfuric acid being a ligand would affect how it reacted.

I'm not going to attempt this reaction, again I value my arms, head and other bodily extensions too much to risk it. I was just curious about the reaction.

P.S. You still haven't answered my original question. Would it go;

'Hydrazine-Sulfate + Sodium Hydroxide ----> Hydrazine + Sodium Sulfate + Water

[Edited on 18-2-2012 by Hexavalent]

woelen - 20-2-2012 at 00:46

Yes, the reaction goes as you write it. Hydrazinium sulfate can be compared somewhat to ammonium sulfate. Ammonium + hydroxide gives ammonia + water. Hydrazinium + hydroxide gives hydrazine + water.

Distilling anhydrous hydrazine is VERY dangerous. There is a serious risk of explosion. Anhydrous hydrazine is an unstable compound.

Distilling hydrazine hydrate is more safe and can be done without risk of explosion, but I would not do it in a glass apparatus. Hydrazine is said to slowly attack glass when it is hot. I do not have personal experience with that, but I would not risk my expensive distillation equipment on that. Hydrazine hydrate at room temperature does not attack glass, I have some of this and it stores fine in a glass bottle for years already.

Also keep in mind that hydrazine is a known carcinogen. A single whiff will not lead to instant cancer, but it certainly is not good to be exposed to hydrazine vapor.

If you are inexperienced (and I draw that conclusion, given your question about the equation), then I would say: Stay away from hydrazine and also from its salts. There are many other equally interesting things to play around with which are less risky.

Hexavalent - 20-2-2012 at 03:51

Thanks for your help Woelen. Again, I have no intention of distilling it, I was merely speculating about the reaction. As for hydrazine salts, erm . . .its kinda too late . . . as I mention in my publication in MemberPublication, I have already prepared just under 30 grams!:)

I do, however, understand the risks involved. I work outside with a fan blowing downwind to my side, I wear a lab coat, chemical splash goggles and nitrile gloves and sometimes even a face shield or respirator.

It finally came to me a few minutes ago; is this correct;

N2H4-H2SO4 + 2 NaOH = Na2SO4 + 2 H2O + N2H4

[Edited on 20-2-2012 by Hexavalent]

Engager - 20-2-2012 at 08:12

Quote: Originally posted by Hexavalent  
I understand that liquid Hydrazine can be prepared by the dry distillation of Hydrazine Sulfate and a base (namely NaOH), all done under inert atmosphere conditions. Can anyone enlighten me on the balanced equation for this reaction?

N2H4-H2SO4 + NaOH ----> N2H4 + ??

[Edited on 18-2-2012 by Hexavalent]

Then in solution reaction is actually two step, since hydrazine acid sulphate has weak solubility adding 1 eq. of NaOH will form perfectly soluble dihydrazinium salt:

2 N2H6SO4 + 2 NaOH => (N2H5)2SO4 + Na2SO4 + 2H2O

If one more eq. of strong base is added, free hydrazine solution is formed:

(N2H5)2SO4 + 2NaOH => 2N2H4 + Na2SO4 + 2H2O

So complete freebase eq. is:

2 N2H6SO4 + 4 NaOH = > 2N2H4 + 2Na2SO4 + 4H2O

Reaction is perfectly usable to prepare solutions of hydrazine, those can be made anhydrous for example using KOH solution in ethanol with hydrazine sulphate will give anhydrous ethanol/hydrazine solution with precipitation of potassium sulphate, insoluble in ethanol. Note that hydrazine is very toxic, in both free state and in form of the salts.

[Edited on 20-2-2012 by Engager]

Hexavalent - 20-2-2012 at 09:23

So . . .your last equation is essentially what I said, but using twice the amounts for every compound involved?

Engager - 20-2-2012 at 09:51

Yes. It's the same, i've just added little detail about reaction, since dibasic salts of hydrazine and monobasic ones, poses whole new properties and chemistry. In many cases it's actually very important witch group of salts you are using.

Ephoton - 21-2-2012 at 19:02

Engager your idea of using KOH and hydrazine sulfate in alcohol will not make anhydrous hydrazine in alcohol
as you are still creating one mole of water for every mole of hydrazine sulfate (or two moles of freebase hydrazine)

You need to use an alkoxide to do this.

Back onto the distillation of hydrazine. I would love to get some clean non alcohol solvated hydrazine and have
read that they normally distill this stuff in a silver retort.

Silver is very expensive do you think other metals would work as well for distilling this substance.

Neil - 21-2-2012 at 19:06

Could you get away with silver plated copper?

Engager - 21-2-2012 at 20:48

Quote: Originally posted by Ephoton  
Engager your idea of using KOH and hydrazine sulfate in alcohol will not make anhydrous hydrazine in alcohol
as you are still creating one mole of water for every mole of hydrazine sulfate (or two moles of freebase hydrazine)

You need to use an alkoxide to do this.

You are certainly right about that, thanks for correction.

[Edited on 22-2-2012 by Engager]

Rosco Bodine - 21-2-2012 at 21:30

This may be a "beginnings" topic but is definitely obscure enough to not have been adequately covered in texts or references which I have ever seen, so it is really a very good question and not so elementary at all.

Freebasing of anhydrous hydrazine in alcohol could be a possible usefulness for aluminum amalgam in isopropyl alcohol or magnesium in methanol. This could certainly be of usefulness in a sodium azide synthesis or for other syntheses where an anhydrous "tincture of hydrazine" is needed. I have never tried this,
but now it is definitely on my "to do" list of interesting experiments.

Also there is an anhydrous double salt of calcium sulfate and sodium sulfate
which could also be useful in alternative freebasing schemes for hydrazine, using a combination of sodium hydroxide and calcium hydroxide. This could also be useful in schemes for forming hydrazine salts such as the nitrate or perchlorate in aqueous solution by double decomposition schemes.

Ephoton - 22-2-2012 at 05:57

Yes I should probably have thought more about that Neil :)

I have also wondered if it were possible to use ether for the solvent that was used for freebasing
the hydrazine into then use the mixture for birch reduction there after.

it may be possible to even dry a wet solution of hydrazine and ether with KOH and then just filter it
meaning that the need for freebasing to anhydrous is not needed.

The ether should be evaporated long before the hydrazine so it may actualy be a safe way to do birch.

Do you know rosco if anhydrous solutions of hydrazine are sensative or is it just the pure compound itself ?

also would not freebasing the dihydrazine sulfate produce water as well if it was done with an alkali hydroxide.

dont amines complex with calcium salts ?

[Edited on 22-2-2012 by Ephoton]

Rosco Bodine - 22-2-2012 at 10:54

Hydrazine is stable but it is very chemically reactive. Yeah freebasing dihydrazine sulfate does produce byproduct water but only half as much with respect to the yield of freebased hydrazine as is byproduct water from freebasing hydrazine sulfate. Possibly the extreme solubility of the dhydrazine sufate is such that a lesser total byproduct water would be involved in freebasing even when a hot aqueous concentrated solution of the dihydrazine sulfate might
be added dropwise to aluminum isopropoxide for the purpose of preparing an anhydrous tincture of hydrazine in isopropanol, which could be filtered from the byproduct aluminum sulfate. What may be the dangers attendant to such a process I do not know. But it seems like it could be done. I have never seen this described anywhere so it may be novel. This is not a recommended experiment for a beginning or novice chemist....this would be more advanced.

[Edited on 22-2-2012 by Rosco Bodine]

woelen - 22-2-2012 at 23:36

Anhydrous hydrazine is not very stable. Even at room temperature it easily decomposes and its shelf life is limited, due to decomposition (formation of N2 and NH3). Certain catalysts can cause anhydrous hydrazine to decompose very violently. I certainly would not feel comfortable with anhydrous hydrazine around, due to pressure buildup in the bottle and the chance of spontaneous violent exothermic decomposition.

Hydrazine hydrate is much more stable. Hydrazine hydrate is a true chemical entity with formula N2H4.H2O. It is a colorless fuming liquid at room temperature. I have a small amount of pure hydrazine hydrate and this material keeps well. In practice, however, I hardly do any experiments with this, I prefer doing experiments with salts of hydrazine, such as N2H4.2HCl. The free aqueous base gives off fumes which are very toxic, the salts can be handled without any fuming issues.

Rosco Bodine - 23-2-2012 at 00:16

Hydrazine is stable enough for storing in fuel tanks of spacecraft for months or longer. The descent stage of the Mars lander Phoenix used hydrazine. Evidently there are adequate methods for long term storage. The cover story for the shootdown of the USA-193 spy satellite is complete disinformation, especially dubious being the part of the cover story about the hydrazine. What the Russians said about this shootdown simply being a test of a weapons system was precisely correct.

For purposes of synthesis an alcohol solution of hydrazine would likely be prepared and used as an intermediate and would not be stored so stability may not be an issue. And whatever level of hydration is desired could be controlled
so this still seems like a valid experiment, but because of the unknowns it definitely is no benign sort of process.

[Edited on 23-2-2012 by Rosco Bodine]

Rosco Bodine - 25-2-2012 at 12:54

The differing solubilities of Hydrazine Sulfate and Dihydrazine Sulfate may be exploited to advantage in schemes for freebasing hydrazine in order to obtain differing states of hydration for the freebased hydrazine. I am posting this in different threads because it is pertinent in all of them.

I don't have a chart for the solubility curves, so I borrowed this excerpt via printscreen screenshot, you know sort of ripped it ......sharing is caring

Hexavalent - 2-3-2012 at 14:09

Thanks Rosco, I like your motto:)

Rosco Bodine - 4-3-2012 at 23:28

<embed type="application/x-shockwave-flash" src="" width="350" height="24" style="undefined" id="ply" name="ply" quality="high" allowfullscreen="false" allowscriptaccess="always" flashvars="file= e=80&autostart=false"></embed>

The Wand Of Alchemy

The fabled Wand of Alchemy
In Uther's realm now veiled by sea
Outside and in with castled view
Once on earth and under true
'Tis far beneath the shining dream
Of sun and moon, or starlight's gleam
When these orbs sheds tears of gold
A mirrored splash it sees unfold

'Tis far beneath the shining dream
Of sun and moon, or starlight's gleam

Where lies the Wand of Alchemy?

For each kilogram of vehicle and payload to ascend from the surface of Mars and to reach Mars orbit will require about six kilograms of hydrazine fuel. Conversely a similar mulitplier is applicable to the descent from Mars orbit to the surface
if a parachute or some other aerodynamic braking is not used to lower the fuel requirement for powered descent as would be necessary if there was no atmosphere available for braking. Even so, it can be seen that the task of soft landing on Mars a return vehicle and then returning that ascent vehicle to orbit and rendezvous will require a lot of fuel.

Attachment: Mars Sample Return Probe Hydrazine Ascent Engine.pdf (1.4MB)
This file has been downloaded 801 times