Determination of the
Atomic Weight of Cadmium.
Introduction and Historical statement.
A careful examination of the literature on the atomic weight of cadmium will convince any one that considerable uncertainty yet remains in reference to this constant. Six experimenters have worked on this problem but the results of no one of them can be accepted as being more accurate than those of all others. The value assigned to cadmium varies from 111.48 to 112.32 on the basis of oxygen = 16. The best work has apparently been done by von Hauer, Lenssen and Huntington. The results of these three seem entitled to about equal confidence, yet the figure obtained by von Hauer differs from that of Huntington by three tenths of a unit.
The more prominent difficulties which have been encountered were:
First. The preparation of cadmium compounds free from all impurities, and which at the same time were well adapted to weighing.
Second. The lack of a thoroughly simple and exact method for the analysis of cadmium compounds.
Third. Insufficient care in weighing in many cases whereby small errors were introduced into the results.
The methods which have been employed are:
1 Conversion of the metal into the oxide. (Stromeyer).
2 Conversion of the sulphate into the sulphide. (von Hauer and Partridge).