It is obviously of the highest importance in controlling the action of a solution to find out what strength of cyanide and alkali it contains at any given time. Under this head are the tests for free cyanide, “total” cyanide, hydrocyanic acid, and free or “protective” alkali.
Besides these cyanide constituents, which have to be determined frequently each day, it is useful at times to ascertain the presence, (and if present the amount), of the following substances, zinc, copper, ferrocyanide, and sulphocyanate.
It is customary to express cyanide strength in terms of potassium cyanide (KCN) of 100% strength, even though sodium cyanide (NaCN), carrying a higher percentage of cyanogen (CN) per unit of weight, may be actually in use.
This seems somewhat illogical and the only thing to be said in its defence is that the theory and practice of cyanidation having been born and having grown up under the formula KCN a change of notation would mean readjustment of all the old standards and, for a time at least, a mental translation of the new notation to the old before it would convey any meaning. In view of the varying cyanogen content per unit of weight in the commercial cyanide now put ….Read more