Dissolve g in carbon dioxide-free water R prepared from distilled water R and dilute to 100 ml with the same solvent.
Appearance of solution
The freshly prepared solution is clear and colourless.
Dissolve g in 50 ml of distilled water, add 1 ml of M sodium hydroxide and dilute to 100 ml with the same solvent.
to for the freshly prepared solution S.
Sulphates and sulphites
Maximum per cent.
To 10 ml of solution S add ml of a freshly prepared 50 g/l solution of sodium nitroprusside. The solution does not become violet.
Maximum 10 ppm.