Permafteni Colcun of Opake Bodies. . 1 99 



ciple, it can hardly be doubted that the differ- 

 ence between mild calcareous earth, and quick- 

 lime, is alfo occafioned by a communication, or 

 deprivation, of the fame principle. 



The origin of fixed air, feems to prove its phlo- 

 giflic nature. For all bodies, which yield it, af- 

 ford alfo inflammable matter: but many of them 

 do not yield any acid. Calcareous fpar, magnefia, 

 and alcaline falts, fend forth fixed air, and all 

 thefe fubftances, by the lofs of it, are deprived of 

 their inflammable contents : diamonds, expofed 

 to the focus of a burning glafs under a receiver, 

 impart to the air, contained in it, a power of pre- 

 cipitating lime, from lime water, when it is agi- 

 tated with it. But it does not appear that any 

 acid can be derived from thofe bodies. 



Some of the properties of fixed air are confiflent 

 with either the charader of acid, or of phlogifton. 

 Such are, its power of altering the colour of vege- 

 table juices ; its affinity to alcalies; and ready 

 union with lime ; its power of diflblving iron, 

 which is inflanced in all acids, and in the phlo- 

 eifticated alcaline lixivium ; the antifeptic quality 

 prevails equally in acids, and in inflammable 

 fpirits ; acids are difengaged from fubftances, 

 vvhichare decompofed by ftronger acids, phlo- 

 gifton is likewife expelled from bodies, which 

 are diflTolved in acids. 



The qualities of acid, and phlogiflon, agree in 

 thcfe, and in feveral other inftances, but fixed air 



O 4 IS 



