O = 16. C = 12.003 S = 32.059 At.Wt.Cd. 1ˢᵗ series, CdC₂O₄ : CdO = 12.66368g. : 8.10031g. 111.816. 2ⁿᵈ ” CdSO₄ : CdS = 15.93505g. : 11.02691g. 111.727. 3ʳᵈ ” CdC₂O₄ : CdS = 16.85228g. : 12.12906g. 111.610. difference, 0.206. As Clarke has pointed out when those values are chosen for carbon and sulphur which are founded on the best experimental evidence the agreement between the different series of results as calculated by Partridge is somewhat modified. I have repeated the work on which series I is based and would call attention to the following points in which it appears to have been experimentally defective. 1 The metal was only distilled twice in a vacuum. It has been found in this laboratory that perfectly pure cadmium or zinc can be prepared only by repeated distillations, each one being carried on slowly to allow the impurities to separate by means of their difference in volatility. 2 The supposed mixture of metal and oxide resulting from the decomposition of the oxalate was only moistened with a few drops of nitric acid in order to reoxidize any reduced metal. Unless the entire mass of metal and oxide was dissolved there would be danger of the presence of free undissolved metal which would possess an appreciable vapor-tension below the temperature of decomposition of cadmium nitrate. An appreciable loss in weight resulting from a distillation of the metal out of the crucible might easily result. 3 It seems very probable that the cadmium nitrate was not heated sufficiently to remove all traces of the oxides of nitrogen. I have found that this could only be accomplished by long continued heating. Constant weight was not sufficient to have decided this point since it was also found that this could be reached short of complete decomposition, if the temperature was too low to remove the last traces of these oxides. Some very delicate test for such oxides should have been applied at the end of each experiment. The following table contains a summary of the results thus far obtained. When two values are given for one series of determinations, the first is calculated from the total material used and the total product found, the second is an average of the results of the separate experiments. Oxygen is taken as 16 throughout. Date. Investigators. At.Wt.Cd. 1818, Stromeyer, 111.483 1857, von Hauer, 111.935 } 111.940 } 1859, Dumas, 112.322 } 112.241 } 1860, Lenssen, 112.043 } 112.067 }