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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



The sulphate produced was dried at 400°, and afterwards examined 

 for free sulphuric acid, giving a correction which was applied to the 

 weighings. The corrected weight is given above. Any impurity in the 

 sulphate would tend to lower the apparent atomic weight of cadmium, 

 and therefore the result is believed by the author to be a minimum. 



Finally, Bucher examined the oxide method followed by Morse and 

 Jones. The syntheses of oxide were effected in double crucibles, first 

 with both crucibles porcelain, and afterwards with the small inrier crucible 

 of platinum. Two experiments were made by the first method, three 

 by the last. AVeights and percentages (Cd in CdO) as follows: 



Cd. 



1.2G142 

 .99785 



CdO. 



1.44144 

 1.14035 



Percentage. 



87.511 

 87.504 



.0024 



Mean, 87.-1 



.0016 



The two means given above, representing work done with porcelain 

 and with platinum crucibles, correspond to a difference of about 0.2 in 

 the atomic weight of cadmium. Experiments were made with pure 

 oxide of cadmium by converting it into nitrate and then back to oxide, 

 exactly as in the foregoing syntheses. In each case the oxide obtained 

 at the end of the operation represented an increase in weight, but the 

 increase was greater in platinum than in porcelain. Hence the weighings 

 of cadmium oxide in the foregoing determinations are subject to constant 

 errors, and cannot be trusted to fix the atomic weight of cadmium. 



A different class of determinations relative to the atomic weight of 

 cadmium are those of Hardin,' who effected the electrolysis of the chloride 

 and bromide, and also made a direct comparison between cadmium and 

 silver. The aqueous solutions of the salts, mixed with potassium cyanide, 

 were electrolyzed in platinum dishes. The cadmium* which served as 

 the starting point for the investigation was purified by distillation in 

 hydrogen. All weights are reduced to a vacuum. The data for the 

 chloride series are as follows, with a column added for the percentage 

 of Cd in CdCl, : 



1 Journ. Ainer. Chem. Soc, 18, 1016. 1896. 



