Sciencemadness Discussion Board

Failure to isolate Calcium Cyanate

Daffodile - 16-3-2019 at 22:39

Hey guys, just hoping for an explanation or insight into why my procedure isn't working.

I'm attempting to make pure calcium cyanate, so I did the urea/ sodium carbonate melt to collect a product of solid off-white sodium cyanate.

To remove contaminants such as sodium carbonate, the crude sodium cyanate was dissolved in 50% hot acetic acid.

The resulting solution was then mixed with aqueous calcium chloride, expected was the calcium cyanate product.

Instead I have nothing. Does anyone have suggestions for why this might not be working?

Metacelsus - 17-3-2019 at 00:34

The acid step might have decomposed your cyanate. It's known to hydrolyze to carbon dioxide and ammonia under acidic conditions, especially when hot.

I think adding acid to remove the carbonate is OK as long as you don't add excess acid. Carefully monitor the pH and make sure the solution doesn't become acidic.

[Edited on 2019-3-17 by Metacelsus]

draculic acid69 - 17-3-2019 at 03:15

Adding acid to sodium cyanate will decompose it when hot for sure it's also a terrible way to purify it,you need to dissolve in hot water and add ethanol and let the plates that form precipitate and then filter I forget the amounts of water/ethanol to naocn but it's in the literature somewhere I've done it this way many times to purify the rxn products of sodium carbonate and cyanuric acid.its a low yeilding procedure so next time I'll use urea instead I reckon it will give a better result.ill try NaOH instead of carbonate and try to capture the nh3 byproduct which comes off as the carbonate which is harder to capture.all in all acids are not a great way to purify this substance.

CharlieA - 17-3-2019 at 16:32

Daffodile: Do you have a literature reference for this reaction, by any chance?

Daffodile - 17-3-2019 at 17:03

Which one?

The Urea decomposition is fairly common knowledge (ie:

More details on formation of Calcium Cyanurate here:


It looks like free cyanic acid polymerizes pretty fast? Not really relevant but anyway. The acetic acid addition was my own idea, since I thought it would dissolve all the contaminants mentioned in the patent without affecting the cyanate/ cyanurate. Maybe the desired product is too soluble to precipitate? I am unable to find a literature Ksp value but I assumed it was pretty low. On second thought I was probably wrong and the calcium cyanate/ cyanurate is decently soluble considering the properties of similar salts.

draculic acid69 - 18-3-2019 at 02:26

Sodium cyanate is water soluble but not very .11.6g in 100 ml.