Use
Crystallise thioformamide from EtOAc, Et2O or ether/pet ether. The monohydrate is a yellow oil soluble in many organic solvents. UV: 263nm ( 2500) in MeOH. [Erlenmyer & Menzi Helv Chim Acta 31 2071 1948.] Alternatively dissolve it in Et2O to separate it from any formanide and/or polymers, filter, evaporate and recrystallise the residue from EtOAc at Dry-Ice temperature [Londergan et al. J Am Chem Soc 75 4456 1953]. Store it in Et2O solution over P2O5. [Cousineau & Secrist J Org Chem 44 4351 1979, Beilstein 2 H 95, 2 I 39, 2 III 128, 2 IV 92.]