208 



SOLUTIONS OF SULPHURIC ACID 



It is thus seen not only that the precipitating point is a per- 

 fectly definite one, but that it can be determined with consider- 

 able accuracy. 



The next question is, whether it expresses accurately th& 

 amount of acid present. 



Column I. contains the concentration of H 2 S0 4 in mixture in 



gramme-molecules per litre. 

 " II. contains the concentration of CuSO 4 in mixture in 



gramme-molecules per litre. 

 " III. contains the amt. of H 2 8O 4 in grammes, calculated to 



be in every 5 c.c. of mixture. 



" IV. contains the same, as found in every 5 c.c. of mixture. 

 " V. contains the percentage error. 



We thus see that by this means, the sulphuric acid present 

 can be determined with considerable accuracy. 



In the above analyses, the mixture under analysis was dilu- 

 ted very much, the reason being, that so far the work has been 

 only to find a good method of analysis, and not to prove or 

 disprove the presence of acid sulphate. 



But now a number of analyses were performed on the above 

 mixtures, keeping the mixtures concentrated, and in no case was 

 there any appreciable difference in the amount of caustic potash 

 needed before precipitation would commence. 



The results obtained from analyses of the concentrated mix- 

 tures, gave, as a rule, slightly less quantities of sulphuric acid. 

 But this I would attribute to the fact that the precipitate would 

 be more easily noticed in the smaller volume than in the larger^ 



