carbonic
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Hydroxylamine/Fremy's Salt (potassium nitrosodisulfonate) failure - help debug?
I was trying to make some Fremy's salt just for fun via sodium hydroxylamine disulfonate but I could not get the hydroxylamine to crystallize.
I intended to create the SO2 in-situ using bisulfite and bisulfate, because I didn't want to deal with SO2 gas. The reaction seemed to work (NaOH
test gave strong ammonia odor) but the hydroxylamine would not precipitate
6g of sodium nitrite and 9g of sodium acetate in 50ml dH2O mixed and cooled to 0C in ice-salt bath. 10g of sodium bisulfite in 20ml dH2O added and
mixed. 10g of sodium bisulfate in 20ml dH2O + ice chips added slowly to keep temp below 2C.
When the bisulfate was added, tan/yellow color appeared and disappeared, NO? compound perhaps? After addition was complete, stirring continued for
20min with still no precipitate.
5ml sample of the light yellow liquid was added to 5ml 5% NaOH solution, creating strong ammonia odor. Acetone added to this mixture did not an oxime
make. Because the ammonia odor, I expect some hydroxylamine was created as it is very distinguishable from the odors of the constituents.
I wonder if the problem was dilution? When bubbling SO2, the H2O content recommended is less than what I used so I suspected too little SO2. A
second sample had 2g more bisulfate and 2g more bisulfite solutions added with still no precipitate. So SO2 in-situ is not very active perhaps? The
gas is needed?
I don't have any use for Fremy's salt other than it has interesting dia/paramagnetic qualities, but I'd like to debug the hydroxylamine step before
trying again. Any suggestions?
I see another ref for Fremy's salt that uses bicarbonate + nitrite + SO2 + oxidation. It makes me wonder if the acetate is really worth anything, or
just a sodium donor for the hydroxylamine.
http://www.answers.com/topic/fremy-s-salt?cat=technology
Edited to add another ref: This preparation uses bisulfite and glacial acetic so now I am very puzzled why my simple bisulfate acid would not create
the hydroxylamine. Perhaps if I try again I will just attempt to oxidize in-situ like they do.
http://chemistris.tripod.com/science/synthesis_of_fremys_sal...
[Edited on 6-3-2008 by carbonic]
Edit by Chemoleo: Title
[Edited on 9-3-2008 by chemoleo]
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carbonic
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Wow, dead silence on the equivalent of vinegar/baking soda volcano! I can see now that some of the "experts" giving so much opinion on the
hydroxylamine thread are most skilled at speculation.
But I agree, reading text book and typing is a lot easier than actually doing things. Less glassware to clean for sure! So I continue to march on.
Not to worry, it's all good. Bisulfite (even when mixed 1:1 with bisulfate) is not going to eject molar quantities of SO2. So a good idea is to go
1.8x or even 2x for fun. A second error in my post is the omission of......
XXXXXX
And re-trying the experiment with bisulfite. bisulfate, nitrite, and XXXXXX gives a small, but worthwhile, crystal dump. XXXXXX and HCL is less bulky
and even a bit easier to temp-control. It is indeed important to live below 3C at the bloody most.
[Edited on 9-3-2008 by carbonic]
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Nicodem
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Insulting everybody in general will surely not help you in getting any reply!
If I were you I would rather think if I described the problem properly enough.
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chemoleo
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I also don't see what the insulting is about.
Indeed Fremy's salt did not ring a bell with me, but potassium nitrosodisulfonate would have.
Also, reaction equations always help if you wan't to attract a greater audience.
Your post essentially presumes intricate knowledge of the reaction (actually more than one), or a willingness to look things up - a presumption that
probably doesn't hold for 95% of the members if the former isn't true. Several times I had to check with your post (see the below) to really
understand what you are doing.
I suggest you adjust your description in the future so that you get the audience you want to attract. I certainly won't make the effort the next time.
Foremost, you don't say why you expect the SODIUM hydroxylamine disulfonate salt to precipitate/crystallise?
Perhaps if you started with the potassium salt you'd get the preciptate you are after, indeed Jander & Blasius describes an experiment with the
pot. salts, which indeed works by bubbling SO2 into KNO2 and KAc. The temperature MUST also not rise above 0 deg C.
All things I had to look up, and of which you made no mention.
In the second link you posted, a very good description of the experiment is given (the prep of Fremy's salt, which is prepared from the hydroxylamine
disulfonate), which matches nicely with one in Jander & Blasius, which I've just checked.
It is clear that the glacial acetic acid is needed to generate nitric acid HNO2 (check reaction equations), are you using the bisulfate instead? How
much? Is the quantity sufficient, or is there too much? Stoichiometry?? The J&B prep, nor the link above, say that any precipate is to be expected
at this step, why do you expect one?
Then of course you are not doing the KMnO4 oxidation step (I'm not sure you are after Fremy's salt after all), with the NH3 addition, to oxidise the
hydroxylamine to the nitroso form.
If you want to make hydroxylamine HCl via its disulfonate, then bubble SO2 into 40g KNO2/ 50 g KAc in 850 ml ice/H2O (temp < 0 deg C), until the
solution smells of SO2. During this reaction the potassium hydroxylamine disulfonate sequesters. The salt is soluble in extra acid,
so if you are doing the experiment with too much bisulfate vs bisulfite, (see above, when you are trying to avoid SO2 gas) , you'll get soluble
hydroxylamine disulphonic acid. Therefore no precipitate. 
Try to be a bit more careful in what you do next time ( stoichiometries, pH, cations) , and I'm pretty sure it'll work out.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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carbonic
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| Quote: | Originally posted by Nicodem
Insulting everybody in general will surely not help you in getting any reply!
If I were you I would rather think if I described the problem properly enough. |
Good point, my comments were out of line.
Thanks chemoleo for your review, it is appreciated.
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