Molybdenum(V) is quantitatively precipitated as sulphide (99.7%) from 0.1 M At hydrochloric acid without formation of molybdenum blue and without need for a long digestion. Precipitation is more complete and co-precipitation less than with Mo(VI) sulphide. The precipitate can also be used directly for gravimetric estimation. In the presence of EDTA, molybdenum(V) sulphide is not precipitated from 0.1 M hydrochloric acid and can be separated from copper, bismuth, antimony and tin sulphides and determined cerimetrically in presence of the EDTA.