PURPOSE: To recover a thiourea compsn. by allowing a sulfuric sludge of petroleum origin to react with urea and to utilize the compsn. as a source of fertilizing material or as a component of a fertilizing formulation.

CONSTITUTION: Water is added to a sulfuric sludge of petroleum origin contg. 50-99 wt.% sulfuric acid and 1-20 wt.% org. residue in such a way that the molar ratio between water and all the acid in the sludge ranges from about 1:1 to 6:1. Urea is then added to the sludge in such a way that the molar ratio between urea and all the acid in the sludge ranges from about 1:1 to 4:1 and they are brought into reaction at 20-75°C under atmospheric pressure. The resultant soln, is decanted and the objective thiourea compsn. contg. 15-31 wt.% nitrogen is recovered.