E. A. Partridge — Atomic Weight of Cadmium. 377 



Art. XLYIII. — A Re-determination of the Atomic Weight 

 of Cadmium ; by Edw. A. Partridge, M.A., B.S. 



The atomic weight of cadmium has been determined by 

 Stromeyer, Yon Hauer,* Lenssen,f Dumas;}: and Huntingdon. § 

 With = 16 for the basis of calculation the values obtained 

 by these experimenters are the following : by Stromeyer 111-48, 

 by Yon Hauer 111-96, by Lenssen 112-08, by Dumas 112-25, by 

 Huntington 112'24. From these results Clarke calculates 

 112-092 to be the most probable figure, and concludes his article 

 on the subject with this remark : " It will be seen that 

 Dumas's and Huntingdon's determinations both made* with 

 haloid salts of cadmium agree with wonderful closeness and so 

 confirm each other. On the other hand, Yon Hauer's data 

 give a value which is much lower. Apparently Yon Hauer's 

 method was good, and the reason for the discrepancy remains 

 to be discovered. Until that is ascertained, I prefer to use the 

 above mean value rather than to adopt one investigation and 

 reject the others." 



This investigation was undertaken with the hope of arriving 

 at a value for the atomic weight of cadmium more reliable 

 than that given by former experimenters. 



The following points were regarded as of first importance : 



1st. The most scrupulous care in the purification of themate- 

 i-ials used in every stage of the work. 



2d. Avoidance of any method in which the reactions in- 

 volved were uncertain or doubtful. 



3d. The utmost care and refinement in weighing. 



4th. Use of a large number of determinations as the basis 

 of calculation. 



At the outset much time was devoted to making a pure 

 cadmium salt by recrystallization of the sulphate, and much 

 work was devoted to accumulating a stock of this as the start- 

 ing point. This, however, was discarded in favor of the metal 

 obtained by distillation. 



The literature upon this subject is interesting, though some- 

 what meager. Mercury has been purified by distillation for 

 years. Demarcayf in 1882 observed that zinc and cadmium 

 are volatile in vacuo at comparatively low temperature, and 

 suggests this as a means of purification. In 1884, Schuller^f 



* Jour, tiir Prakt. Chemie, xxii, 350. 



flbid., lxxix, 281. 



% Ann. Chem. Pharm., lxiii, 27. 



§ Proc. Amer. Acad., 1881. 



|| Comptes Rendus, xcv, 183. 



4f Ann. d. Phys., xviii, 320, and Jahresbericht 1884, 1550. 



