5. Ascorbic acid solution (flow-analysis): Dissolve 6 g of ascorbic acid, C6H8O6, in pure water. Add 20 ml of glycerol, 50 ml of methanol and 2 ml of a surfactant (Levor-IV or Aerosol-22 diluted 1:10 with pure water). Make up to 2 L with pure water. Store dark in a brown bottle at < 8 ˙c, the reagent is stable for about one mouth as long as it remains colourless.
6. Mixed reagent ( manual method): Dissolve 12.5 g of ammonium heptamolybdate tetrahydrate, (NH4)6M07024 . 4H2O, in 125 ml of pure water. Also dissolve 0.5 g of potassium antimony tartrate, K(SbO)C4H4O6 , (with or without 1/2H2O), in 20 ml of pure water. Add the molybdate solution to 350 ml of sulpuric acid (reagent 1 ) while continuously strrring. Add the tartrate solution and mix well. Store in a laboratory glass bottle. This mixed reagent is stable for several months.