380 E. A. Partridge — Atomic Weight of Cadmium. 



which the porcelain crucible was placed, was forced into a cir- 

 cular hole cut in a piece of asbestos board 13 cm square. The 

 top of the nickel crucible was flush with the upper surface of 

 the board, the joint being air tight. 



Ten experiments made by the above method gave the fol- 

 lowing results : 



Series I. 



Weight of 



cadmium oxalate 



taken. 



09898 

 21548 

 10711 

 17948 

 16066 



1-17995 



7.. 1-34227 



8 1-43154 



9. 

 10. 



1-53510 

 1-41311 



Weight of 

 cadmium oxide 

 found. 



•70299 



•77746 

 •70807 

 •75440 

 •74237 

 •75471 

 •85864 

 •91573 

 •98197 

 •90397 



Atomic 

 weight. 



Ill 



111 



111 



111 



111 



111 



111 



111 



111 



111 



819 

 793 



755 

 780 

 783 



784 

 829 

 823 

 821 

 834 



Total 12-6636! 



8-10027 



(111-8027) 



Mean value. 111-8027 



Maximum, ___ 111-834 



Minimum 111-759 



Difference 



Probable error 



•075 

 •010 



Another method used for the determination of the atomic 

 weight of cadmium is that of Von Hauer. It consists in 

 reducing cadmium sulphate to cadmium sulphide in a stream 

 of hydrogen sulphide and observing the loss of weight. A& 

 the result obtained by Yon Hauer is considerably lower than 

 those obtained by other experimenters, doubt has been cast upon 

 its accuracy. The following possibilities have been suggested as 

 tending to make Yon Hauer's results low : 1st. That the cad- 

 mium sulphate as weighed by him contained hygroscopic mois- 

 ture. 2d. That the presence of metallic iron in the ferrous sul- 

 phide used in making the hydrogen sulphide would lead to the 

 generation of hydrogen and consequent reduction and volatil- 

 ization of cadmium. 3d. That some cadmium sulphide might 

 have been volatilized in the stream of hot hydrogen sulphide. 



It was, therefore, determined to carry out a series of experi- 

 ments by this method in order to determine if any of these 

 objections were well grounded. 



In the experiments about to be described, the first danger 

 was overcome by weighing the sulphate in stoppered glass 



