162 THE ATOMIC WEIGHTS. 



series is followed by a similar one with cadmium bromide, the latter 



having been sublimed in vacuo. Results as follows : 



CdBr 2 . AgBr. Ratio. 



4.39941 6.07204 7 2 .454 



3.18030 4-38831 7 2 .472 



3.60336 4.97I5 72.480 



4.04240 5-58062 72.453 



3.60505 4.97519 72.461 



Mean, 72.464, .0035 

 Huntington found, 72.4216, .0028 



General mean, 72.438, .0022 



In order to fix a minimum value for the atomic weight of cadmium, 

 Bucher effected the synthesis of the sulphate from the metal. 1.15781 

 grammes of cadmium gave 2.14776 of sulphate. 



Hence Cd =.- 111.511. , 



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 inner cruci- 

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

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



Cd. CdO. Percentage. 



{1.26142 1.44144 87.511 



.99785 1.14035 87.504 



Mean, 87.508 



^1.11321 1.27247 87.484 



4 1.02412 1.17054 87.491 



(2.80966 3.21152 87.487 



Mean, 87.487 

 Mean of alias one series, 87.495, .0035 



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 weigh- 

 ings of cadmium oxide in the foregoing determinations probably are 

 subject to constant errors, and cannot be trusted to fix the atomic weight 



