I would like to report on my recent attempt (presumed successful) at the production of sodium cyanate from sodium carbonate (calcined baking soda) and
urea according to a procedure modified from US patent #4000249.
135 grams of urea and 141.6 grams of sodium carbonate were heated to 170 degrees Celsius and maintained at that temperature for three hours. This was
then allowed to cool to around 80 degrees Celsius and 55.5 grams of water was added. This was heated to dryness (125 degrees Celsius) and 61 grams of
urea was mixed in. The mixture was heated to 160 degrees and maintained at that temperature for 10 hours. The urea/water addition procedure was
repeated with 35 grams of water and 3.6 grams of urea and the mixture was reheated to 160 degrees for 3 hours. As a warning to any who would want to
try this, a large amount of ammonia is produced throughout the procedure, especially on addition of water.
The end product was composed of white granules of variable fineness which were ground to a homogeneous powder. I'm unsure how to assay the purity but
my first thought was to weigh out a sample, react it with HCl, dry it and then reweigh it. As a quick subjective test, I reacted a spoonful with
dilute acetic acid, causing much bubbling and an acetic stench (possibly isocyanic acid, possibly just an aerosol of acetic acid from all the
bubbling).
As a final word, I would like to ask the community if they know any means to assay the purity of my sample. entropy51 - 23-7-2010 at 17:43
As a quick subjective test, I reacted a spoonful with dilute acetic acid, causing much bubbling and an acetic stench (possibly isocyanic acid,
possibly just an aerosol of acetic acid from all the bubbling).
Na2CO3 does bubble when dilute acetic acid
is added, so you for sure need a better test. Have you tried looking up a test for cyanate? Some of us kinda like to see that you made an effort to
sort things out.12332123 - 23-7-2010 at 18:35
I did consider that carbonate would also bubble, I was hoping to go on smell and possible production of cyamelide (there did seem to be some white
insoluble particles left, though these could just be reaction products from the self-condensation of urea). kclo4 - 23-7-2010 at 19:09
I'd say try a few different things... I'm sure it is sodium cyanate though, but it is always good to check.
Quote:
The reaction can be demonstrated by starting with solutions of potassium cyanate and ammonium chloride which are mixed, heated and cooled again. An
additional proof of the chemical transformation is obtained by adding a solution of oxalic acid which forms urea oxalate as a white precipitate.[3]
- wikipedia
There you can try to do a titration on it. Mix your sodium cyanate with ammonium chloride, heat than cool -- then slowly add small known amounts of
oxalic acid into it in intervals, waiting for the solution to clear and the white precipitates to fall to the bottom. When it does not appear that
anymore is precipitating, than figure out how much you have...
.. ought to be able to figure out the cyanate content of your sample that way...
If that doesn't work, as it may not... try solubility, if it has a big enough difference from that of sodium carbonates. This will tell that it is
present, but not to what extent.
Perhaps another test is, IF calcium cyanate is soluble and stable in water, you ought to be able to add your sodium cyanate too a calcium chloride
solution - if nothing precipitates, this would imply you've made cyanates with little to no carbonates present -- if it becomes white and cloudy,
there is a good chance that it has a large amount of carbonate still present.
You might be able to purify it better by recrystallization.. eh?12332123 - 23-7-2010 at 20:14
Recrystallization is effectively a no-go unless I am willing to use liquid ammonia as a solvent (which I am not), as it is effectively insoluble in
most other solvents with exception of water in which it hydrolyses so easily as to make purification by recrystallization impossible! kclo4 - 23-7-2010 at 21:20
I didn't think that the hydrolysis was significant, though I guess it is?
either way, good luck! Let us know how it turns out.
the rest is chinesse but that was the only patent i found that describes what i did.
actually it's done in 15 minutes.
i used methylsulfonylmethane as the solvent.
all i did afterwards was dissolve in water, filter out the msn, and then precipitate the alkali cyanate by adding alcohol.
The invention discloses a method for preparing high-purity potassium cyanate, which belongs to preparation of the potassium cyanate. The method takes
industrial urea and potassium carbonate as raw materials and dimethyl sulfoxide or dimethyl formamide as a solvent, and adopts proper technological
conditions: the reaction temperature is 130 DEG C, the reaction time is 8 hours, the mol ratio of the urea to the potassium carbonate is 3.5 to 1, and
the mass ratio of the solvent to the urea is 7 to 1; the product with 96 percent (mass fraction) of the potassium cyanate can be obtained, and the
obtained potassium cyanate is washed by adopting anhydrous alcohol as a detergent, wherein the amount of the detergent is 3 to 4 times of the volume
of the potassium cyanate; and the potassium cyanate after washing is dried, and the potassium cyanate with the purity of more than 98 percent (mass
fraction) can be obtained. The method has the advantages that the technology is simple and easy and the purity of the prepared potassium cyanate is as
high as more than 98 percent (mass fraction).
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theMagpie - 30-10-2010 at 17:24
Interesting. Have you done any characterization tests that would prove it is cyanate, eg, the cobalt acetate test I linked upthread?madscientist - 4-11-2010 at 09:07
A more easily purified product is prepared from NaOH and urea. NaOH is very soluble in alcohol while cyanate is not (particularly in cold isopropyl
alcohol.)
cyanate
cyanureeves - 4-11-2010 at 11:07
madscientist are you saying that excess naoh will remain in solution and the cyanate can be separated? how about with koh?also ive read here that it
has been prepared in tin cans even.but wouldnt that have a large amount of ferrous contamination if tin is ferrous?ive read that it is difficult for
titanium to form cyanide salts. would a titanium cannister be suitable for this task then?europa - 4-11-2010 at 13:35
Titanium should be fine... steel cans too, unless you need it to be extremely pure for some reason. I've done this in a steel can before, and I've
never noticed any contamination issues.
NaOH/KOH are both soluble in alcohol; NaOCN/KOCN are not. You can shake the mixture with 99% alcohol and filter out the cyanate.
