SCHEDULE 2 METHODS OF ANALYSIS

PART I

8b. DETERMINATION OF DIFFERENT FORMS OF NITROGEN IN THE SAME SAMPLE — IN THE ABSENCE OF CYANAMIDE NITROGEN

“4.26    REAGENTS

Indicator solutions:

4.26.1 Mixed indicator: Solution A: dissolve 1 g methyl red in 37 ml 0.1 M sodium hydroxide solution and make up to 1 litre with water. Solution B: dissolve 1 g methylene blue in water and make up to 1 litre. Mix 1 volume of solution A and 2 volumes of solution B. This indicator is violet in acid solution, grey in neutral solution and green in alkaline solution; use 0.5 ml (10 drops) of this indicator.

4.26.2 Methyl red indicator solution: Dissolve 0.1 g methyl red in 50 ml 95% ethanol, make up to 100 ml with water and filter if necessary; 4 – 5 drops of this indicator can be used instead of the previous one.