THE MOLECULAR THEORY 



347 



Cannizzaro's method of determining atomic weights. 



The method used by Cannizzaro in determining the atomic 

 weight of an element depends on setting out in a table all 

 those volatile compounds the vapour density and percentage 

 composition of which are known. From the vapour density 

 the molecular weight is calculated, whilst the percentage 

 composition gives the weights of the different constituents 

 in the molecular weight of the compound. 



The substance of Cannizzaro's table 1 is set out in the 

 first three columns of the following series of tables : 



i. HYDROGEN COMPOUNDS. H=i. 



1 Cannizzaro gives a general table and a series of special tables for 

 the individual elements. In the following paragraphs the general table 

 has been subdivided, and a few additional substances, quoted in 

 Cannizzaro's special tables, have been added. The values for ozone 

 and for phosphine have been corrected. 



