lO Ta\'LOR, Volumetric Dcteniiinatioit of Cobalt. 



weighed as pyrophosphate. In method B tlie cobalt was 

 separated by the well-known nitrite method, precipitated 

 by potash, and weighed as metal. Method C was the 

 volumetric method I have described. The results are 

 again in percentages of monoxide : — 



A. B. G. 



23'8- 23'65- 23-5. 



In this last experiment the result by the volumetric 

 method is rather low, as compared with the others. In 

 the other series of four experiments, also, the results in 

 column C are on the whole lower than the others. If we 

 assume, however, the composition of the precipitated 

 oxide to be represented by the formula Co;,0,4, then the 

 factors for the thiosulphate become "00531 of metallic 

 cobalt, and 00675 of the monoxide. Using these factors 

 instead of those previously given, the amount for the 

 method C in the last experiment becomes 23"8, and those 

 in column C in the series of four experiments (see page 9) 

 become 



4'93 



4-89 



390 



5 "37 

 In either case the results by the volumetric method 

 are evidently fairly accurate, and, as the process itself is 

 very short indeed compared with the other methods used 

 (the nitrite process takes 2 or 3 days), I have no doubt it 

 will be useful to chemists engaged in the analysis of 

 cobalt ores. 



Central School, Manchester. 



