7.Mixed reagent (flow-analysis) : Dissolve 10 g of ammonium heptamolybdate tetrahydrate,(NH4)6MO7O24 . 4H2 , in 600 ml of pure water. Carefully add 120 ml concentrated of sulphuric acid (d= 1.84 g/ml) and mix. Add 20 ml of a solution of 2.3 g potassium antimony tartrate, K (SbO)C4H4O6 . nH2O in 100 ml of a solution of 2.3 g potassium antimony tartrate, K (SbO)C4H4O6 . n H2O in 100 ml of pure water. Mix well. Mix well and make up to 2 L. This mixed reagent is stable for several months.