66 OXYGEN AND HYDROGEN GASES. 



the last edition of my System of Chemistry, and 

 in my Essay on the Specific Gravity of the Gases. 

 If we compare the table at the begining of this 

 section, with the specific gravity now found, we 

 will perceive the results of the different experi- 

 menters as follows : 



Saussure's, too high by . . -^\ G th part. 

 Biot and Arago's, too low by . T ^th part. 

 Allen and Pepys's, too low by . j^d part. 

 Thomson's, too high by . . YS^^d part. 

 Berzelius and Dulong's, too low by y^^th part. 



There seems no reason to doubt that Biot and 

 Arago, and Allen and Pepys, took the specific 

 gravity of oxygen gas standing over water, and 

 consequently saturated with moisture. Let us 

 suppose the temperature at which their experi- 

 ments were made to have been 60, and let us see 

 what influence the presence of moisture must 

 have had upon the specific gravity of their gas. 



Let p pressure of the atmosphere, suppose 30 in. mercury. 

 y^elasticity of vapour at 60.=O524 inch mercury. 

 rt=sp. gr. of dry oxygen gas=l-llll. 

 6==sp. gr. of vapour at 6'0.=0.00772. 

 .r=sp. gr. of moist oxygen gas at 60. 



It is well known that 



x ^V~L(a + &)= 1-0992. 



This is nearly the mean between the results of 



