LAVOISIER. 273 



causes combustion, and that no body can burn but in 

 oxygen gas. 



Secondly. The facts are all against his doctrine, that 

 the heat and light conies from the fixation of the gas. 

 Experiments on the capacity of bodies for heat have 

 clearly shewn this. But the simple fact of well-known 

 explosions, as of gunpowder, disproves his theory for 

 here, instead of the heat and light coming from the gas 

 being reduced to a solid state, a gaseous body is formed 

 two or three hundrecj times the bulk of the solid ex- 

 ploded. 



Thirdly. There are many acids which have no oxygen 

 in their composition, and there are many bodies con- 

 taining oxygen which have none of the qualities of 

 acids. The first part of this proposition was not cer- 

 tainly known to Lavoisier, and he assumed that the 

 acids which had not yet been decomposed would be 

 found to contain oxygen. The second part of the pro- 

 position was known to him, and ought to have checked 

 his generalization. We now know many acids which 

 contain no oxygen at all. Muriatic acid, a compound of 

 chlorine and hydrogen; prussic acid, a compound of 

 hydrogen, nitrogen and carbon; hydro-bromic ; fluoric- 

 acid; ferro-cyanic acid; sulpho-cyanic ; hydro-selenic ; 

 hydriodic: xanthic. Even if fluoric be omitted, here 

 are nine undeniable acids, and all without a particle 

 of oxygen in their composition. Again, the mere 

 fact of calcination should have prevented him from so 

 generalizing, for all calces contain oxygen, and many of 

 them have no acid qualities. Indeed, his own conjec- 

 ture, since fully confirmed by experiment, that the fixed 

 alkalis are oxides, is a still more striking disproof of his 



T 



