250 LAVOISIER. 



general theory. This theory is well known. It consists 

 in supposing that all combustion, like all calcination, is 

 produced by the union of oxygen with the body burnt or 

 calcined; and that the gas which, in calcination, only 

 gives out its heat and light slowly and imperceptibly, 

 unless when this operation is performed very rapidly, in 

 combustion gives out that heat quickly and sensibly. 

 Thus the doctrine is, that, by applying heat to a com- 

 bustible body, we so far overcome the attraction of co- 

 hesion as to make the particles enter into a union with 

 those of the gas, which gives out its latent heat and 

 light, thus causing the flame that marks and distinguishes 

 the process. Calcination, too, may be produced so 

 quickly, that the process is attended with red heat, and 

 even with flame. Iron burns with a bright whitish and 

 sometimes a bluish flame, gold with a duller and more 

 lambent flame of a greenish colour. 



The product of the combustion, slow or quick, was next 

 attentively considered by M. Lavoisier. In the case of 

 metals it was their calces, or as he denominated them 

 from the process of oxygenation, oxides. In the case of 

 sulphur he had found it to be vitriolic acid, of phos- 

 phorus phosphoric; nitrous gas, which he erroneously 

 supposed the base of nitrous acid, formed that acid by its 

 union with oxygen. The nature of fixed air, too, was no 



by "published" he means read at the Academy, this maybe correct, 

 for it appears to have been read 5 Sept., 1777, but the volume was 

 not published till 1780. In the same volume we find internal evi- 

 dence that the other papers referred to in the text were read in the 

 opening of that year; thus, one of them read in May refers to 

 experiments about to be performed in company with M. Trudaine 

 and M. Montigny, the former of whom died in August, 1777. 



