264 Dr. Thomas Thomsons Experiments on the 



strength. But after it had been diluted with a certain 

 proportion of water, the sulphate of lime precipitated to 

 the bottom, and the pure acid was drawn off. This hap- 

 pended, when the acid was so much diluted, as to be com- 

 posed of 



1 atom acid, ... 5 



5 atoms water, . . 5*625 



10625 



1. Specific Gravity of different Atomic Compounds of Sul- 

 phuric Acid and Water. 



As an atom of sulphuric acid of the specific gravity 1*8422 

 weighs 6*125, and as it is a compound of 1 atom acid and 

 1 atom water, it was easy, by mixing determinate weights 

 of this acid and water, to obtain compounds of 1 atom acid 

 with 2, 3, 4, 5, 6, 7, 8, 9 and 10 atoms water. The follow- 

 ing table exhibits the specific gravities of all these strengths. 



The third column in the preceding table was calculated 

 on the supposition, that the bulk of the acid and water 

 united underwent no change, but continued the same after 

 combination as before it. By comparing this column with 

 the second, which shows the actual specific gravities of the 

 various compounds, we see the change of volume which 

 actually takes place. We see that when an atom of oil of 

 vitriol^ combines with 1, 2 and 3 atoms water, the bulk of 

 the compound diminishes, or the specific gravity is greater 



* I employ this term to denote a compound of 1 atom acid and 1 atom water. 



