7 " 21.4 " 21.4 "
These show that large variations in bulk must be avoided.
~Effect of Varying Ammonia.~--The quantities of copper and acid were the
same as in the series of experiments last noticed. The bulk was 200 c.c.
The results were:--
Dilute ammonia 20.0 c.c. 30.0 c.c. 50.0 c.c. 100.0 c.c.
Cyanide required 20.9 " 21.7 " 22.3 " 24.6 "
~Effect of Varying Acid.~--The quantities of copper and water were the
same as in the last-noticed set of experiments: 30 c.c. of dilute
ammonia were used.
Nitric acid 5.0 c.c. 10.0 c.c. 15.0 c.c.
Cyanide required 21.6 " 21.7 " 21.5 "
On adding nitric acid to the solution it combines with a portion of the
ammonia to form ammonic nitrate; it will be seen from the last series of
experiments that the lessening of the amount of free ammonia will
decrease the quantity of cyanide required; but, on the other hand, the
ammonic nitrate which is at the same time formed will increase the
amount required; under the conditions of the assay these two effects
neutralise each other, and such differences in the quantity of acid as
are likely to occur are unimportant.
~Effect of Varying Ammonic Salts.~--The quantities of copper, water, and
ammonia were the same as in the last mentioned set of experiments, but
no nitric acid was used.
Pages:
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374