The total alkali is determined by incinerating a weighed sample in a platinum dish, dissolving the residue in water, filtering and titrating the filtrate with standard acid.
When cadmium is not present the copper may be precipitated by boiling the acidulated ammoniacal solution with test lead and titrating, as before described, without removing the lead and copper from the solution.
The ferrocyanide solution is standardized by dissolving i gramme of pure zinc in 6 cc. of hydrochloric acid, adding ammonium chloride, and titrating as before.
The potassium cyanide solution is standardized by dissolving 0.5 gramme o£ pure copper in 5 cc. of nitric acid, diluting, adding io cc. of ammonia, and titrating exactly as described above.
A few drops of starch solution are then added, and when the blue colour has nearly vanished a drop or two of methyl orange makes the end reaction very sharp. The thiosulphate solution is standardized by dissolving o 3 to o 5 gramme of pure copper in 3 cc. of nitric acid, adding 50 cc. of water and 5 cc. of ammonia, and titrating as above after the addition of 5 cc. of glacial acetic acid and 5 cc. of the potassium iodide solution.
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