Sodium cyanate

Sodium cyanate (NaOCN) is a reagent used to prepare ureas and organic isocyanates. Despite the name, it's not very toxic. It is possible to reduce sodium cyanate to the infamous poison sodium cyanide, but I won't be doing this for obvious reasons. I'm interested in using sodium cyanate to synthesize semicarbazide.

I prepared sodium cyanate from sodium carbonate and urea.

To a metal pot I added 13.4g of anhydrous sodium carbonate. I heated the pot strongly for 10 minutes to ensure the sodium carbonate was truly dry. After this, I added 5.75g of urea with stirring.
The urea almost immediately melted and decomposed. The urea addition must be performed outside because large amounts of toxic ammonia gas are produced. Anyway, I added 2 more 5.75g portions of urea separately with stirring. After all the urea had been added (and the mixture was dry) I added 90ml of water. Glacial acetic acid was added until the mixture reached pH 6. I filtered the mixture, collecting the clear filtrate. Then I added 100ml of ethanol and stirred.

A fine precipitate of sodium cyanate formed. I collected the sodium cyanate via filtration and dried the product. 2.43g of sodium cyanate was obtained.

(NH2)2CO ==> HOCN + NH3   /   2 HOCN + Na2CO3 ==> 2 NaOCN + H2O + CO2