Thiophosphoric acid
Thiophosphoric acid is a chemical compound. Structurally, it is the acid derived from phosphoric acid with one extra sulfur atom, although it cannot be prepared from phosphoric acid. It is a colorless compound that is rarely isolated in pure form, but rather as a solution. The structure of the compound has not been reported, but two tautomers are reasonable: SP3 and OP2SH.Preparation
The compound has been prepared in a multistep process starting with the base hydrolysis of phosphorus pentasulfide to give dithiophosphate, which is isolated as its barium salt:
In a second stage, the barium salt is decomposed with sulfuric acid, precipitating barium sulfate and liberating free dithiophosphoric acid:
Under controlled conditions, dithiophosphoric acid hydrolyses to give the monothioderivative:
H3PO2S2 + H2O → H3PO3S + H2S
