206 SOLUTIONS OF SULPHURIC ACID 



Purification and Analysis of Copper Sulphate. 



The copper sulphate was obtained as chemically pure, and 

 after careful re-crystallization, was found to be free from iron 

 and the members of the ammonium sulphide group. 



The copper sulphate solutions were analysed by precipitating 

 the sulphate, in known volume, with barium chloride, and weigh- 

 ing as barium sulphate. 



The following are the results of three analyses of the same 

 solution : 



Cu S0 4 in 5 c.c. of solution = .5782 grammes. 



= .5788 

 = .5790 



Mean = .5787 



These figures would seem to show that my results might be 

 in error about 0.1 per cent. 



Purity and Analysis of Sulphuric Acid. 



The sulphuric acid was the best obtainable from Merck, and 

 was taken as chemically pure. The sulphuric acid solutions 

 were analysed volumetrically with standard caustic potash, 

 using as an indicator phenol phthalein. 



The following results show with what accuracy such analyses 

 could be carried out : 



2 c.c. H 2 S0 4 solution contained .1627 grammes H 2 S0 4 



" .1624 



Mean - .16253 " 



Thus, the possible error of a single measurement would seem 

 to be about 0.11 per cent. 



Preparation and Analysis of Mixtures. 



Equal volumes of the simple solutions, whose concentrations 

 and densities were known, were mixed at 18C. The density of 

 the mixture being obtained, the concentration of the mixture 

 with respect to each of the constituents, was obtainable. 



