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Volume 38, 1905
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(b.) Ammonia.

Precipitation was caused by a definite volume of normal ammonium-sulphocyanide in the presence of excess of zinc-sulphate. After washing the precipitate with a small quantity of a dilute solution of zinc-sulphate, the ammonia in the filtrate was estimated by distillation with caustic soda. It was thus possible to determine the amount of ammonia in the double salt.

The method of operation will be illustrated by means of the detailed analytical results obtained in the case of quinine.

Preliminary Test Experiment.—10 c.c. N ammonium-sulphocyanide on distillation with caustic soda gave ammonia =10 0 c.c.N acid. The filtrate from 10 c.c.N/10 quinine and 10 c.c. N ammonium-sulphocyanide gave ammonia = (i) 9·5 c.c. N acid, (ii) 9·5 c.c. N acid. ∴ 1 c.c. N quinine combines with 0·5 c.c. N ammonia.

(c.) Sulphocyanide.

The method has already been described and explained.

The following is a summary of the results obtained in the determination of ammonia and sulphocyanide:—

(1.) Quinine-ammonium-zinc-sulphocyanide: 10 c.c. N/10 quinine required (a) 0·5 c.c. N ammonia and 3·5 c.c.* sulpho-

[Footnote] * The mean of a large number of closely concordant determinations.

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cyanide, (b) 0·5 c.c. N ammonia. Calculated for 6B, 4Zn (CNS)2, 3 NH4CNS, 10 HCNS, 0·5—3·5 c.c. sulphocyanide.

(2.) Cinchonine-ammonium-zinc-sulphocyanide: 10 c.c.N/10 cinchonine required (a) 0·5 c.c. N ammonia and 3·0 c.c.* sulphocyanide, (b) 0·55 c.c. N ammonia. Calculated for 4B, 3Zn (CNS)2, 2 NH4CNS, 4 HCNS, 0·5—3·0 c.c. N sulphocyanide.

(3.) Cocaine-ammonium-zinc-sulphocyanide: 20 c.c. N/20 cocaine required (a) 0·5 c.c. N ammonia and 2·5 c.c. * N sulphocyanide, (b) 0·55 c.c. N ammonia. Calculated for 6B, 2Zn (CNS)2. 3 NH4CNS, 8 HCNS, 0·5—2·5 c.c. N sulphocyanide.

[Footnote] * The mean of a large number of closely concordant determinations.