ig6 Mr. Delaval on the Caufe of the 



of cryflalling depends upon their union with that 

 principle. 



He heated, in a filver vcflel, a lixivium of mild 

 alcali, which imparted to the filver a covering, or 

 coating, of inflammable matter, by which its fur- 

 face was tarniflied, and became black. The lixi- 

 vium was feveral times poured out of the filver 

 veflel, and after the furface of the filver had been 

 freed from the tarnifh, the lixivium was replaced 

 in it, and again heated, by which the tarnifh was 

 renewed. This was repeated till the lixivium no 

 longer communicated any ftain to the filver. 



The caufticity of the lixivium increafed, in pro- 

 portion as it imparted its phlogifton to the fur- 

 face of the filver, and, at the end of the procefs, 

 the alcali became perfeflly cauftic, and incapable 

 of cryftallizing. 



Thefe infi:ances, and many others which might 

 be adduced, feem to prove that the change, which 

 fi:4ed air produces in cauftic alcaljes, is not effcded 

 by acid, but by phlogiftic matter. 



It is certain that the matter, communicated to 

 lime by fixed air, is the very fame which it im- 

 parts to alcalies. For it may be transferred, un- 

 changed, from one of thofe fubftances, to the 

 other; and, when united to either of them, ftill 

 retains the fame ^«rt/i//Vj'. Therefore, if phlogifton 

 renders alcalies mild, and efFcds their cryftal- 

 lization, the fame principle alfo precipitates lime, 



and. 



