§ 42. CALOULATIOX OF RESULTS. 43 



This may be effected by a rule-of-three calculation also, 

 in which the molecular weight cf the insoluble sub- 

 stance is made the first term, the weight of the substance 

 sought in a molecule of the insoluble substance the second, 

 and the weight of the insoluble compound found the third. 



For example, in a determination of sulphuric acid, SO3, 

 1.13 grm. of baric sulphate was found; then we have 



BaSO^ : SO3 = BaSO, : SO3 



233 : 80 = 1.13 : 0.3879 grm. 



The same result can be more expeditiously obtained, 

 however, with the aid of Table III, Avhere for each special 

 case a part of this calculation has already been perform- 

 ed, namely, the division of the second term by the first ; 

 nothing is left to be done, therefore, but to multiply the 

 weight of the insoluble compound found, whose name is 

 given in the first column, by the decimal in the second 

 column against the name of the substance sought in the 

 third column. In the above-mentioned case we find, on 

 consulting the table, the proper .decimal against the 

 names sulphuric acid and baric sulphate is 0.3433, -w hich 

 multiplied into 1.13 grm. = 0.3879. 



