Acknowledgement.
The author wishes to acknowledge his indebtedness for advice and instruction to Professor Morse at whose suggestion and under whose guidance this work has been carried on. He also wishes to express his thanks for instruction to Professor Remsen in Chemistry, Professor Williams in Mineralogy, Dr. Ames in Physics and Mr. Hulburt in Mathematics.
Introduction and Historical Statement.
The atomic weight of cadmium has been investigated by a number of chemists but the results obtained vary between wide limits. The work described in this paper was undertaken with the object of finding the cause of the discrepancy in some of the methods employed. A complete historical statement has been given by Morse and Jones, (Amer. Chem. Jour., 14. 261.) and it is only necessary, here, to give a summary for the purpose of reference:
| Ratio. | At. Wt. Cd. | ||
|---|---|---|---|
| 1818, | Stromeyer, | Cd : CdO | 111.483 |
| (Schweiggers Jour. 22, 336.) | |||
| 1857, | Von Hauer, | CdSO4 : CdS | 111.935 |
| (Jour. f. Prakt. Chemie 72, 338.) | |||
| 1859, | Dumas, 1st series. | CdCl2 : Ag | 112.416 |
| 2d „ | CdCl2 : Ag | 112.007 | |
| (Ann. Chim. Phys. [3], 55, 158.) | |||
| 1860, | Lenssen, | CdC2O4 : CdO | 112.043 |
| (Jour. f. Prakt. Chem. 79, 281) | |||
| 1882, | Huntington and Cooke, | CdBr2 : AgBr | 112.239 |
| „ „ | CdBr2 : Ag | 112.245 | |
| (Proceedings Amer. Acad. 17, 28) | |||
| 1890, | Partridge, 1st Series | CdC2O4 : CdO | 111.816 |
| „ 2d „ | CdSO4 : CdS | 111.727 | |
| „ 3d „ | CdC2O4 : CdS | 111.616 | |
| (Amer. Jour. Sci.[3], 40, 377) | |||
| 1892, | Morse and Jones, 1st Method, | Cd : CdO | 112.0766 |
| 2d „ | CdC2O4 : CdO | 112.632 | |
| 1892, | Torimer and Smithy | CdO : Cd | 112.055 |
| (Zeit. f. Anorg. Chem. I. 364) | |||
In this summary as well as in the rest of this paper the following atomic weights are used:
| Oxygen | = | 16.00 |
| Sulphur | = | 32.059 |
| Carbon | = | 12.003 |
| Chlorine | = | 35.45 |
| Bromine | = | 79.95 |
| Silver | = | 107.93 |
The Oxalate Method
Preparation of Pure Cadmium.
“Cadmium met. puriss. galv. reduc”, obtained from Schuchardt, was used for preparing pure cadmium. It was heated to redness in a current of hydrogen which had been purified by washing with both acid and alkaline solutions of potassium permanganate. This treatment converted the metallic powder into a bar which could be distilled in a vacuum. The metal was then distilled nine times in the same manner that Morse and Burton, Amer. Chem. Jour. 12, 219, had distilled zinc. All distillations were made slowly except the last one, which was made quite rapidly.