Salts. igi 



Vitriol is formed in thefe ftones by expo- 

 (ing them a long time to the action of the 

 air and moifture, or by torrefadion in open 

 air, and fubfequent expofition to its aftion, 

 which operation in fome cafes muft be often 

 repeated, according to the proportion of ful- 

 phur, and the nature of the Earth ; the cal- 

 careous pyrites are thofe in which it is moft 

 eafily formed, and they effloreice the fooneft, 

 good pyrites properly treated, yield about ^ 

 of their weight of vitriol. 



Vitriol is alfo prepared from mineral waters 

 that hold copper in folution, which is preci- 

 pitated by iron ; this foUition of iron is after- 

 wards cryftalizedand always retains forrtfj cop- 

 per. In Hungary it is prepared from pyrita- 

 ceous fhiftus, and in many places from a fpe- 

 cies of calamine; the vitriol of goflaar com-, 

 monly contains a portion of zinc, as that of 

 Hungary and Saxony does of copper; the 

 'Englifh and French vitriols are purer, yet 

 fometimes contain a fmall proportion of alum. 

 Turf and peat are fometimes impregnated 

 with vitriol; other earths alfo often contain 

 vitriol and alum. Mon. Mineral. 460. This 

 vitriol is fometimes found of a white colour 

 on the borders of the mineral lakes of Tufcany. 

 1 6 Roz. 36 3 1 



SPECIES IX. 



