490 abstracts: analytical chemistry 



tion; and (b) calculation from the oxidizing value of the permanganate, 

 derived from some accurate oxidimetric standard, such as sodium oxa- 

 late. The former would be more satisfactory, provided a simple and 

 accurate means of obtaining a known amount of manganese is avail- 

 able. Otherwise the latter is preferable, tho it involves the use of a 

 conversion factor, which may be either theoretical or empirical. Since 

 Brinton and others claimed that the sodium oxalate values were 1 per 

 cent lower than those derived from manganous sulfate, the subject was 

 studied in detail. 



A study of the standardization of permanganate with sodium oxalate 

 showed that the conditions recommended by McBride must be slightly 

 modified for use with 0.03 N permanganate, the strength usually employed 

 for the bismuthate method; since the relative errors caused by variation 

 in conditions with 0.03 N permanganate may be much larger than with 

 0.1 N. By the use of a small volume in the titration the errors from 

 this source are reduced to a minimum. 



After it was found that heating for a considerable period at temper- 

 atures of 450-500° is necessary to obtain anhydrous normal manganous 

 sulfate, and that the salt does not begin to decompose unless heated 

 above 550°, solutions of known manganese content were prepared by 

 dissolving a definite weight of manganous sulfate which had been heated 

 to constant weight at 450°-500°. 



A study of the effect of conditions upon the bismuthate oxidation, 

 showed that for amounts of manganese up to 0.05 gram, accurate results 

 may be obtained over a wide range of conditions, viz., at from 5° to 

 25° in a volume of 50 to 150 cc, containing 20 to 40 per cent nitric acid 

 by volume, filtration after standing one-half minute or one-half hour 

 with bismuthate; addition of ferrous sulfate immediately or after one- 

 half hour. The results were accurate in the presence of as much as 

 3 grams of iron. Addition of phosphoric acid to the ferrous sulfate 

 solution rendered the end points more distinct. The only conditions 

 found which yielded inaccurate results were (a) deficiency of nitric 

 acid, (b) failure to agitate after addition of bismuthate, and (c) allowing 

 the solution to stand after addition of the excess of ferrous sulfate. For 

 analyses of rich ores and similar high grade materials, the use of 0.1 N 

 permanganate is recommended, permitting the use of about 0.1 gram 

 sample. 



Experiments upon seven permanganate solutions, of different strength 

 (0.03 N and 0.1 N), prepared from different sources, showed that the 

 values derived from sodium oxalate and manganous sulfate agreed in 



