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Author: Subject: Why are my hydrazine sulfate yields so high?
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[*] posted on 8-12-2021 at 09:22
Why are my hydrazine sulfate yields so high?


I know there is an entire thread dedicated to hydrazine, but I never received a single reply to the question that I posted some weeks (or months) ago. I followed NileRed and Chemplayer (they use the same Hoffman degradation of urea to make hydrazine sulfate). In most videos of people making it (people with far stronger chemistry backgrounds than me) they usually get yields of around 48 to 50%. Around 40 grams of sulfate from their usual proportion of sulfates.

I made hydrazine sulfate twice now to make sure I have enough for NHN synthesis. My first attempt used 50% of the reagents used by NileRed as I was a hydrazine virgin. I was expecting a yield of 20 grams at the absolute most (as NileRed got 40 grams) but I ended up a yield of 29 grams... and two days ago I made another batch with the same 50% of the reagents and after drying I weighed what I got and it came at 33.25 grams.

I assume maybe I got more sodium sulfate contamination? I cooled my hydrazine solution to around 13C before doing vacuum filteration. I let the stuff dry for 36 hours before weighing it.

Why is my yield so high? Is there some way I can tell how much hydrazine sulfate vs. sodium sulfate I have?
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[*] posted on 8-12-2021 at 10:44


You got less yield than others but still wonder why your yield is "high"?
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[*] posted on 8-12-2021 at 10:53


No, I got a higher yield proporational to the reagents I used. Like the starting amount of pool chlorinator (10% sodium hypochlorite) that they used was around 355ml. I used only 177ml.

They got yields of 40 grams starting with 355ml, but I got 29 and even 33 grams starting from just 177ml. All other reagents were similarly halved. See what I am saying? I'm sure a good amount of it is hydrazine sulfate (what else could it be?) but I wonder if somehow an excess of sodium sulfate got in, even though I never cooled it below 13 C.
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[*] posted on 8-12-2021 at 11:26


Then you most likely have a lot of sodium sulfate in your product. If you cool it too much sodium sulfate will crystallize out too since you make a lot of it in that procedure and it isn't too soluble.

You can also use HCl instead to neutralize the Na2CO4 and use only the stocheometric amount of H2SO4 that's theoretically required to neutralize all the hydrazine (but 70% of that amount should be enough). That way you form more soluble NaCl.
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[*] posted on 8-12-2021 at 11:59


In that case I will need to use much more of the sulfate to freebase to make sure I get the quanities I need for NHN synthesis. I plan on two attempts, so I guess diving my stuff into 30 grams each should assure enough hydrazine sulfate is in there.

Edit: Also another question about HCI. Is the store-bought muratic acid pure enough for making hydrazine sulfate? I wanted to use it, but I wasn't sure about the purity.

[Edited on 8-12-2021 by ManyInterests]
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[*] posted on 8-12-2021 at 12:16


Quote: Originally posted by ManyInterests  
No, I got a higher yield proporational to the reagents I used. Like the starting amount of pool chlorinator (10% sodium hypochlorite) that they used was around 355ml. I used only 177ml.

They got yields of 40 grams starting with 355ml, but I got 29 and even 33 grams starting from just 177ml. All other reagents were similarly halved. See what I am saying? I'm sure a good amount of it is hydrazine sulfate (what else could it be?) but I wonder if somehow an excess of sodium sulfate got in, even though I never cooled it below 13 C.


This is why yields are given as percentage, to avoid confusion. When your HCl is colorless it is probably fine to use as is.
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[*] posted on 8-12-2021 at 12:54


Quote: Originally posted by ManyInterests  


Edit: Also another question about HCI. Is the store-bought muratic acid pure enough for making hydrazine sulfate? I wanted to use it, but I wasn't sure about the purity.


I have tried this reaction with success using 'diggers' brand HCl purchased from a hardware store. It is known to contain some metal contamination, but seemingly not enough to overly impact yields.
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[*] posted on 8-12-2021 at 13:03


That sounds good. At any rate I am finished making hydrazine sulfate for a good long time. As far as I see right now the last things on my list are fuming nitric acid, nickel nitrate and freebasing hydrazine. The keto-RDX should be easy to do, albeit I obviously need to do it VERY carefully...

Quote:
This is why yields are given as percentage, to avoid confusion. When your HCl is colorless it is probably fine to use as is.


I figured. But I just find it hard to believe that I would get higher yields than more experienced chemists like NileRed and Chemplayer.
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[*] posted on 8-12-2021 at 13:49


You can titrate the hydrazine with permanganate, quite convenient since you dont need indicator i believe.
one time i attempted to make hydrazine and all of the "product" turned out to be sodium sulfate :p
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[*] posted on 8-12-2021 at 13:56


I don't have any permanganate. I highly doubt all my end product is sodium sulfate though.
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[*] posted on 8-12-2021 at 15:40


Quote: Originally posted by ManyInterests  
I don't have any permanganate. I highly doubt all my end product is sodium sulfate though.


Not all of it, but some of it might be sodium sulfate, actually if you only use sulfuric acid your end product will very likely be contaminated with sodium sulfate even if you do it correctly. NileRed even mentioned at the end of his video that his hydrazine sulfate contains a small amount of sodium sulfate.
The theoretical yield from your amounts should be around 33g of hydrazine sulfate, in practice you only get a 50% yield, so about 17g. So if your yield is like 40g then it's very likely over half of it is sodium sulfate as the decahydrate.

What you could do is to assume that all 40g are Na2SO4*10H2O, then you calculate how much water it would take to dissolve all of that at room temperature (about 100mL) and recrystallize it in that. Anything that crystallizes at RT is for sure hydrazine sulfate. Then put it in the freezer see if there is some hydrazine sulfate left. (You can tell from the crystals).
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[*] posted on 8-12-2021 at 18:01


That is definitely possible. However that is a worst case scenario for me to assume that I have major sodium sulfate contamination. What I am going to do soon is make the nickel nitrate and try to freebase the hydrazine in the same day. I will use 50% of my current supply (30 grams) and use ethanol and sodium hydroxide to crash it out. If a good amount of hydrazine freebases, then I can call that a success to make some NHN.

Worst case scenario... I'll do one final hydrazine sulfate synthesis, but this time I will put in HCI first and then put the 50% sulfuric acid in it. I really, really want to make one or two good batches of NHN.

On an unrelated note: when purifying some sulfuric acid recently, I accidentally forgot my stirbar in the acid before I let the thing boil. The result is that my stirbar disintegrated in the heat. Most of it was a percipitate in the acid, but there was some shimmering in the suspension. Will that affect anything when I use that sulfuric acid?

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[*] posted on 9-12-2021 at 06:11


Quote: Originally posted by ManyInterests  
I don't have any permanganate. I highly doubt all my end product is sodium sulfate though.


If you're American, check out US Pigment Corp's website if you want some, its very reasonably priced and has a lot of uses.
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[*] posted on 16-12-2021 at 14:43


Quote: Originally posted by theAngryLittleBunny  
actually if you only use sulfuric acid your end product will very likely be contaminated with sodium sulfate even if you do it correctly. NileRed even mentioned at the end of his video that his hydrazine sulfate contains a small amount of sodium sulfate.


BTW NileRed's failure to obtain better crystals isn't due to using sulfuric acid. Crystals which leave no residue on heating can in fact be had in better yield than Mr. Anonymous (55.5%) or Mr. Lerner (~51% based on urea) without other acids, recrystallization, gelatin, or bleach stronger than 7.5%. Technique counts...and for high yield, using fresh or a known concentration of bleach.

So, it isn't us who can say what the deal is.




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[*] posted on 16-12-2021 at 14:53


It's very easy to find out if something is sodium sulphate or hydrazinium sulphate.

Weigh it
Heat it.
Weigh it again.
Sodium sulphate doesn't decompose- it just loses water.
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[*] posted on 16-12-2021 at 16:19


I don't know if I mentioned it here. But I figured out what happened wrong.

My synthesis didn't work. I'm not sure where I went wrong, but here is what happened in my first two attempts. I either A: Did not wait long enough before heating when I added the urea/gelatin solution, B: it didn't react with that correctly at all, or C: Not putting in the hydrochloric acid and just using sulfuric acid.

I should have noticed that when nilered and all the others who made the stuff all saw the hydrazine sulfate precipitate almost immediately after all the sulfuric acid was added. I saw nothing precipitate at all. I just let it cool to 13C before filtering. so basically I am left to assume that all my 'hydrazine' sulfate was actually sodium sulfate with no hydrazine at all.

I did a third and final synthesis with 31.5% hydrochloric acid (the brand I used was ultra-pure, which was good) before adding the 50% sulfuric acid to the mixture. I saw the hydrazine sulfate precipitate almost immediately. I waited until the temperature reached around 16C before filtering to prevent any sodium sulfate from coming into my stuff.

My yield there was small, only around 26 grams. But unlike the previous times, this was mostly (if not entirely) hydrazine sulfate. I know this because when I freebased it it reacted exactly like they showed in the freebasing videos. I made some NHN a few days ago, but I am still letting the final product dry. I will let it dry for another 24 hours before removing it from the glass tray and drying it further with a mild steam bath for an hour or two.
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