ANTOINE LAURENT LAVOISIER 131 



ample, if sulphur is burned under a receiver the product of the 

 combustion is vitrioHc acid; if phosphorus be burned the product 

 is phosphoric acid ; if a carboniferous substance, the product is fixed 

 air, otherwise known as acid of lime (carbonic acid, etc.). 



(Note: I would remark in passing that the number of acids is 

 infinitely greater than has been supposed.) 



The calcination of metals is subject to exactly the same laws, and 

 it is with very great reason that Mr. Macquer has treated it as a slow 

 combustion; thus, 1°, in all metallic combustion there is a liberating 

 of fire matter (maticre du feu) ; 2°, veritable calcination can take 

 place only in pure air; 3°, there is a combination of the air with the 

 substance calcined, but with this difference, that in place of forming 

 an acid with it there results from it a particular combination known 

 as metallic calx. 



This is not the place to point out the analogy which exists between 

 the respiration of animals, combustion and calcination; I shall return 

 to that in the sequel to this memoir. 



These different phenomena of the calcination of metals and of 

 combustion are explained in a very happy manner by Stahl's hy- 

 pothesis ; but it is necessary with him to suppose the existence of fire 

 matter {matter e du feu) or of fixed phlogiston in the metals, in 

 sulphur and in all bodies which he regards as combustibles; yet if 

 the partisans of Stahl's doctrine are asked to prove the existence of 

 fire matter in combustible bodies, they fall necessarily into a vicious 

 circle and are obliged to reply that combustible bodies contain fire 

 matter because they burn, and that they burn because they contain 

 fire matter. It is easy to see that in the last analysis this is explain- 

 ing combustion by combustion. 



The existence of fire matter, or phlogiston, In metals, in sulphur, 

 etc., is then really only an hypothesis, a supposition which, once admit- 

 ted, explains, it is true, some of the phenomena of calcination and 

 combustion ; but if I show that these very phenomena may be ex- 

 plained In quite as natural a way by the opposite hypothesis, that is to 

 say, without supposing the existence of either fire matter or phlogis- 

 ton In the substances called combustible, Stahl's system will be shaken 

 to its foundations. 



No doubt you will not fail to ask me first what I understand by 

 fire matter. I reply with Franklin, Boerhaave and some of the 



