Browning and Jones — Estimatioyi of Cadmium. 269 



Art. XXX YII. — On the Estimation of Cadmium^ as the 

 Oxide ; by Philip E. Browning and Louis C. Jones. 



[Contributions from the Kent Chemical Laboratory of Tale University — LYII.] 



In an article entitled "The Estimation of Cadmium " * Max 

 Muspratt discusses critically some of the methods in use for the 

 determination of that element. Muspratt finds that the method 

 which involves the precipitation as carbonate, ignition and 

 weighing as oxide gives low results, and he accounts for these 

 results by the well known tendency of cadmium to reduction, 

 especially in the presence of organic matter. To avoid this 

 reduction he dissolved the precipitated carbonate in nitric acid, 

 evaporated to dryness on a water bath, and gently ignited the 

 nitrate to the condition of the oxide. This treatment also gave 

 low results, although the oxide obtained from the ignition of 

 the nitrate was found to contain traces of sulphate from the 

 solution of the cadmium sulphate used. A second method of 

 treatment was to filter and dry the precipitated carbonate and 

 remove as much of it as possible to a weighed porcelain crucible, 

 ignite and weigh by itself. This oxide was found to be free 

 from traces of sulphate.f 



The remainder of the cadmium oxide adhering to the paper 

 was dissolved in pure nitric acid and the solution and rinsings 

 evaporated to dryness and ignited in a weighed crucible and 

 weighed. Here also low results were obtained which, after the 

 extended process of manipulation, would scarcely seem surpris- 

 ing. If, however, Muspratt adds, the oxide obtained from the 

 ignition of the carbonate be taken as Cd^O the results are 

 satisfactory. 



A third modification gives more satisfactory results. The 

 method of treatment is the same as the last mentioned, except 

 that the oxide obtained from the ignition of the carbonate is 

 ignited in a stream of oxygen until no further increase in 

 weight results. 



In a former paper from this laboratory:}; one of us made use 

 of the carbonate method for the determination of cadmium 

 after having separated that metal from copper. The filtration 

 was made on asbestos in a Gooch crucible and the results were 

 most satisfactory. The object of the work to be described is 

 to show that when the carbonate is filtered upon an asbestos 

 felt previously ignited the dangers of reduction are obviated 

 and the carbonate process is both simplified and placed among 

 good analytical methods. The solution used for the work was 

 one of cadmium sulphate, and the standard was determined by 

 evaporating measured and weighed portions to dryness in the 



*.Tour. Sci. Chem. Industry, vol. xiii, 211. 



f Muspratt's theory is that in the ignition of the carbonate the sulphate is dis- 

 sociated, while the ignition of the nitrate does not effect this result. 

 :}: Browning, this Journal, vol. xlvi, 280. 



