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 2s barium sulphate. 
The following are the results of three analyses of the same 
solution :— 
Cu SO, in 5c. of solution = .5782 grammes, 
“ a3 73 = 5788 “cs 
6c - “<c = 5190 “ce 
Mean. .eeens.s seo di 
These figures would seem to show that my results might be 
in error about 0.1 per cent. 
Purity and Analysis of Sulphurie 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 cc. H, SO, solution contained .1627 grammes H, SO, 
«cc “ 1625 “cc 
“cc 6¢ « “ce 1624 “ (73 
Mean a nsereeee= _.l6255 ) & es 
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 18°C. The density of 
the mixture being obtained, the concentration of the mixture 
with respect to each of the constituents, was obtainable. 
