CADMIUM. 157 



Next in order comes Huntington's* work, carried out in the laboratory 

 of J. P. Cooke. Bromide of cadmium was prepared by dissolving the 

 carbonate in hydrobromic acid, and the product, dried at 200, was puri- 

 fied by sublimation in a porcelain tube. Upon the compound thus ob- 

 tained two series of experiments were made. 



In one series the bromide was dissolved in water, and a quantity of 

 silver not quite sufficient for complete precipitation of the bromine was 

 then added in nitric acid solution. After the precipitate had settled, 

 the supernatant liquid was titrated with a standard solution of silver 

 containing one gramme to the litre. The precipitate was washed by de- 

 cantation, collected by reverse filtration, and weighed. To the weigh- 

 ings I append the ratio between CdBr 2 and 100 parts of silver bromide : 



1.5592 grm. CdBr 2 gave 2.1529 grm. AgBr. Ratio, 72.423 



* 3.745 6 5- I 7 2 4 " " 7 2 .4i5 

 2.4267 3.3511 " " 72.415 



* 3.6645 5.0590 " 72.435 



* 3.7679 5.2016 " " 72.437 

 2.7938 3- 8 5 8 3 " " 7 2 .4io 



* i. 9225 2.6552 " " 72.405 

 3-4473 " 4-7593 " " 72.433 



Mean, 72.4216, .0028 



The second series was like the first, except that the weight of silver 

 needed to effect precipitation was noted, instead of the weight of silver 

 bromide formed. In the experiments marked with an asterisk, both the 

 amount of silver required and the amount of silver bromide thrown down 

 were determined in one set of weighings. The third column gives the 

 CdBr 2 proportional to 100 parts of silver: 



* 3. 7456 grm. CdBr. 2 =: 2.9715 grm. Ag. 126.051 

 5.0270 " 3.9874 " 126.072 



* 3.6645 " 2.9073 " 126.045 



* 3.7679 " 2.9888 " 126.067 



* 1. 9225 " 1.5248 " 126.082 

 2.9101 " 2.3079 " 126.093 

 3.6510 " 2.8951 " 126.110 

 3.9782 " 3.1551 " 126.088 



Mean, 126.076, .0052 



According to Huntington's own calculations, these experiments fix the 

 ratio between silver, bromine, and cadmium as Ag : Br : Cd : : 108 : 80 

 112.31. 



In 1890, Partridge f published determinations of the atomic weight 

 of cadmium, made by three methods, the weighings being reduced to 



* Proc. Araer. Acad., 1881. 



t Amer. Journ. Sci. (3), 40, 377. 1890. 



