456 Flora — Estimation of Cadmium as the Oxide. 



Art. XLYIII. — The Estimation of Cadmium as the Oxide ; 

 by Charles P. Flora. 



[Contributions from the Kent Chemical Laboratory of Yale Univ. — cxlii.] 



Cadmium may be simply and accurately estimated by con- 

 verting the carbonate to the oxide by ignition. The oxide of 

 cadmium may be subjected to very intense heat without loss 

 from volatilization ; but in the presence of any carbonaceous 

 matter it is very easily reduced to the metal, which is quite 

 volatile at high temperatures. Consequently, this method has 

 always been subject to more or less change of error where 

 paper filters have been used. The usual course has been to 

 wash thoroughly and then dry the precipitated carbonate, 

 which is then removed as completely as possible from the 

 filter : the latter then being burned separately. Even here 

 there has always been a very appreciable loss, to avoid which 

 various more or less complicated modes of treatment have been 

 offered. As a type of these, we may take that of Max Mus- 

 pratt,* who, after noting that high results were given by the 

 ignition of the nitrate formed by dissolving the precipitated 

 carbonate in nitric acid on account of included sulphate, pro- 

 ceeded as follows : The precipitated carbonate was washed and 

 dried, and as completely as possible scraped free from the 

 filter paper, and then converted to the oxide by gentle igni- 

 tion. This carbonate was entirely free from sulphate. The 

 filter paper was treated with nitric acid and the resulting solu- 

 tion and rinsings brought into a large porcelain crucible and 

 evaporated to dryness. The dry nitrate was gently heated and 

 the weight of the oxide obtained added to that of the mass of 

 the precipitate. Even after this tedious procedure, Muspratt 

 is obliged to suggest that the results will be more satisfactory 

 if the oxide obtained by the ignition of the paper and the 

 residues upon it be calculated as Cd 2 rather than CdO. Evi- 

 dently the method would give satisfactory results if this reduc- 

 ing action of the filter could be avoided, and in former papers 

 from this laboratory, f it has been shown that this may be 

 accomplished by the use of asbestos filters in a Gooch crucible. 

 There is then no danger of loss from reduction, and the carbo- 

 nate method is simplified and placed among the good analyti- 

 cal methods. Recently, however, Miller and Page \ have 

 found that " the carbonate method is the most troublesome and 

 the least satisfactory ;" but these investigators did not use the 

 asbestos filter. 



* J. Soc. Ch. Ind.; xiii, 211 (1894). 



f Browning, this Journal (3), xlvi, 280 (1893) ; Browning and Jones, ibid. 

 (4), ii, 269 (1896). 



% Ch. News, lxxxiv, 312 (1901). 



