TABLE 2. Determination of sulphur in dilute sulphuric acid solutions by four different 



methods. 



a Corrected for in values given. 



The proposed method gives results 0.1 per cent too high when 3.5 

 per cent of sulphur is in solution and 0.3 per cent too high when 8 

 per cent of sulphur is present. This occlusion of salts evidently com- 

 pensates for an error which would cause the result to be low, as can 

 be seen from Table 1 and the experimental data. 



Lunge and Stierling found similar conditions in the precipitations 

 of sulphuric acid in aqueous solution and in the presence of salts. The 

 quick addition of the barium chlorid solution gave erroneous data in 

 aqueous solution and correct results in the presence of salts while the 

 slow addition of the precipitant gave just the opposite. 



The proposed method employs about 7.6 grams of salt calculated 

 as chlorids) and the peroxid method 15 grams or more. 



PRELIMINARY EXPERIMENTS. 



The preliminary experimental work leading up to this method con- 

 sisted in testing the various reagents which have been proposed in 

 methods for the determination of sulphur, varying the temperature, 

 reagents, and time and manner of treatment. The 22 experiments 

 made involved 160 single determinations exclusive of those that were 

 lost on account of faulty manipulation, or seemed valueless from the 

 nature of the reaction. 



Determinations were made by using mixtures of reagents composed 

 of from 1.25 to 3 grams of sodium hydroxid, 5 to 15 cc of water, 0.5 

 to 1 gram of sodium carbonate, 1 to 2 grams of sodium nitrate, 1 to 3 

 grams of magnesium oxid, and from 3 to 10 grams of crystallized 

 magnesium nitrite. 



The treatment of the material with the reagents varied from drying 

 on the steam bath and burning to heating at from 80 to 230 C. for 

 from one and a half to five hours before burning. By these means 



[Cir. 56] 



