Production of thiosemicarbazide

摘要

In the production of thiosemicarbazide comprising the steps of reacting hydrazine and ammonium thiocyanate to form hydrazinium thiocyanate and by-product ammonia, and heating the hydrazinium thiocyanate to effect isomerization thereof to thiosemicarbazide, the improvement which comprises removing the ammonia from the hydrazinium thiocyanate prior to isomerization thereof, whereby the thiosemicarbazide is produced in high yield and purity. Advantageously at least about 80% of the ammonia is removed by steam stripping and/or vacuum distillation and the subsequent isomerization is effected by prolonged heating in the presence of a carbonyl compound such as acetone or acetaldehyde. The thiosemicarbazide is recovered by cooling to effect crystallization, followed by filtration, the mother liquor being recycled as solvent medium for the next batch.