THEORY OF VOLUMES. 57 



gases, both simple and compound, unite with 

 each other in very simple ratios by volume that 

 1 volume of A unites with 1, 2, 3, or more vo- 

 lumes of B ; and that the bulk of the resulting 

 compounds, always bears a very simple and de- 

 finite ratio to that of its constituents, or to that of 

 one of them.* 



This law has been extended by Dr. Prout and 

 others, to vapours, and even to the supposed 

 vapours of bodies which do not exist in the 

 elastic form, except when united with the per- 

 manent gases. For example, if carbon be burnt 

 in 100 cubic inches of oxygen gas, (the weight 

 of which is 34*60 grains,) an equal volume of 

 carbonic acid is formed ; (which weighs 47*26 

 grains,) showing that 1 2*66 grains of carbon have 

 been dissolved and chemically united with 100 

 cubic inches of oxygen, which are thus converted 

 into the elastic state ; and that 2 atoms of oxygen 

 have united chemically with 1 of carbon. In 

 this way it was found, that the specific gravity of 

 carbon vapour is '416, compared with oxygen 

 1 1 1 1 , as determined experimentally by Dr. 

 Thomson.! It was also found that when sulphur 

 is chemically combined with oxygen by combus- 

 tion, an equal volume of sulphurous acid is 

 formed, the specific gravity of which is 2*222, or 



* Memoires D'Arcuiel, 1809, Tom. II. 



f Mitscherlich has maintained recently, that the specific gra- 

 vity of carbon vapour is double the estimate of Prout. He ob- 

 serves, that as it cannot be determined by direct experiment, it 



