In a previous paper1 a study was made of the relation between tensile strength of electrolytic copper and speed of rotation of the cathode. The results obtained were highly satisfactory, and pointed to possibilities of wider application of the process, in enhancing the physical properties, and increasing the tensile strength of brass and other electrolytically deposited alloys, the unsatisfactory nature of which has long been deplored.2 In the paper referred to above, some work was reported on

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... he copper-zinc and the copper-tin alloys, but the time a t hand was inadequate for an exhaustive study of the question, and this paper is the result of further work along these lines. It was decided a t first to discard the cyanide solution, because of the entirely unsatisfactory results which are obtained from it, and to search for some other solution or combination of solutions which might give a less brittle and more coherent deposit. In order to secure the simultaneous precipitation of two metals from the same solution, the single potentials of those metals in that solution must be very close together, or else marked impoverishment must take place. Single potential measurements on solutions of the double cyanides clearly show that the curves are not necessarily coincident, but they are almost parallel and are reasonably close together. Their distance apart will depend to a certain extent on the amount of free potassium cyanide present. A brass is probably deposited from a solution of the mixed cyanides by reason of impoverishment. Reasoning from conditions in this solution, where a brass is known to deposit, to those which must Bennett. Jour. Phys. Chem., 16, 294 (1912). Field: The Electrician, 63, 632 (1909).