1882, Huntington, 1ˢᵗ series 112.239 ” 2ⁿᵈ ” 112.245 1890, Partridge, 1ˢᵗ series 111.805 ” 2ⁿᵈ ” 111.786 ” 3ʳᵈ ” 111.806 In the above calculation of Partridge’s results C = 12. S = 32. In the following carbon is taken as 12.003 and sulphur is 32.059. 1890, Partridge, 1ˢᵗ series 111.816 ” 2ⁿᵈ ” 111.727 ” 3ʳᵈ ” 111.610 After a careful examination of the methods available it becomes evident that no one of them was _per se_ as accurate as the method employed by Morse and Burton,[2] for the determination of the atomic weight of zinc, and more recently by Burton and Morse,[3] for the determination of the atomic weight of magnesium. The method of work was to prepare pure metallic cadmium, to convert a weighed portion of the metal into nitrate by means of pure nitric acid, to decompose the nitrate completely to oxide and to weigh the oxide. [2] Amer. Chem. Journ. X, 311. [3] ib. XII, 219. Preparation of Pure Cadmium. The work of preparing pure cadmium was begun more than two years ago by Mr. W. V. Metcalf with Dr. H. N. Morse. I wish to express here my sincere thanks to him for the material with which the following determinations were made. The cadmium used by him was obtained from Schuchart and marked “Met. prss. (galv.) redus.” The method of purification by fractional distillation in a vacuum, was essentially that employed by Morse and Burton for the purification of metallic zinc. The distillation was carried out in hard glass tubes of the size of ordinary combustion tubing. [Illustration: FIG. 1.] Fig. 1. represents such a tube. A hard glass tube, 600-700 mm. in length, was closed at one end and about 130 grams of cadmium introduced. The walls of the tube were heated and indented at the two points a, and b, with a red-hot file, dividing the tube into three sections marked A, B and C. The open end of the tube was drawn out, bent, and attached to a Sprengel air-pump by means of a rubber tube.