543 ratio as regards ferrocyanide becomes 6Zn = gCd, and the strength of the solution used would be I cc. = 0.00838 gram cadmium. Our results in acid solutions are intermediate between these values and indicate a variation in the composition of the precipitate between the formulas of Hermann and of Wyrouboff. They are confirmed by a statement by Mackay' that it requires about z& per cent. less potassium ferrocyanide to precipitate cadmium than is required by the formula CdK,Fe(CN), or in other

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... ords the cadmium standard is higher than would be obtained by calculation. They are again in direct contradiction to the statement by Furman that the cadmium standard can be obtained from the zinc standard by direct proportion assuming that 2Zn = zCd. In order to ascertain the composition of cadmium ferrocyanide under different conditions analyses of the precipitates must, of course, be made. This work has already been started and while no results have yet been obtained the marked difference in the physical properties of the precipitates seems to confirm the variation in conlposition.