Oceanography

1. Principle

Phosphate reacts with molybdate under acidic conditions to form heteropoly acids which can be converted by suitable reducing agents to form blue compounds of unknown composition. By using appropriate acids and molybdate strength, ascorbic acid as reductant and antimony as colour enhancing species and intensive blue coloured complex is formed with phosphate. When the pH of the solution is 0.8, only phosphomolybdic acid is produced and the formation of silico-molybdic acid is prevented