Flora — Estimation of Cadmium as the Oxide. 457 



The work of the writer upon the carbonate method fully 

 substantiates the previous work from this laboratory. For the 

 determinations given, a solution of cadmium sulphate was used, 

 whose standard was accurately given by the average of a large 

 number of closely agreeing electrolytic determinations. Por- 

 tions of this solution were accurately measured from a burette 

 and diluted to 300 cm3 with hot water. A 10 per cent solution 

 of potassium carbonate was then added, drop by drop, with 

 constant stirring until no further precipitation took place. 

 The whole was then boiled for about fifteen minutes, when the 

 precipitate became granular and quickly settled. It was then 

 filtered upon an asbestos mat in a G-ooch crucible, which had 

 previously been ignited and weighed, and was then carefully 

 washed with hot water. In several cases, washing by decanta- 

 tion was used. The precipitate was then dried and ignited 

 over a Bunsen burner, first gently, then at full red heat until 

 a constant weight was obtained, care being taken to avoid the 

 reducing action of any unburned gas from the burner. 



The following results were obtained : 





CdO taken. 



CdO found. 



Error. 



No. of exp. 



grm. 



grm. 



grm. 



1. 



0-1277 



0-1275 



— 0-0002 



2. 



0-1277 



0-1280 



+ 0-0003 



3. 



0-1277 



0-1272 



— 0-0005 



4. 



0-1399 



0-1391 



— 0-0008 



5. 



0-1399 



0-1399 



±0-0000 



6. 



0-1703 



0-1700 



— 0-0003 



1. 



0*1703 



0-1700 



— 0-0003 



8. 



0-2129 



0*2128 



— o-oooi 



9. 



0*2129 



0-2128 



— 00001 



10. 



0-2554 



0-2554 



±0-0000 



The method is simple in execution, and the above results 

 prove its accuracy. 



Some of the older manuals also give as a method for the 

 estimation of cadmium that of igniting to the oxide the pre- 

 cipitated hydroxide obtained by adding a solution of sodium or 

 potassium hydroxide to the solution containing the salt of cad- 

 mium. Follenius has published* some results obtained with 

 the use of an asbestos filter, and it was decided to try this 

 method in comparison with the carbonate method. As in the 

 experiments with the carbonate, portions of the solution of 

 cadmium sulphate were carefully measured off from a burette, 

 diluted to about 300 cm3 , and heated to boiling. A 10 per cent 

 solution of potassium hydroxide was then added drop by drop 

 and the whole boiled for about fifteen minutes. Upon cool- 

 ing, the precipitate quickly settled in a semi-granular state, 

 *Z. anal. Ch., xiii, 284 (1874). 



