144 A SYSTEM OF 



This is fo ftrongly united with the' 

 calcareous earth, that the latter enters 

 with it into the very criftals of the fait : 

 though by repeated folutions the earth 

 is by degrees feparated from it, and falls 

 to the bottom after every folution. It 

 grows in form of white froft on walls, 

 and under vaults, and in places where it 

 cannot be warned away by the rain. 

 When it contains any confiderable quan- 

 tity of the calcareous earth, its criftals 

 become rhomboidal, a figure which the 

 calcareous earth often affumes in moot- 

 ing into criftals : but when it is purer, 

 the criftals moot into a prifmatical figure. 

 This is a circumftance which necefTarily 

 muft confufe thofe who know the falts 

 only by their figure, and ftiews, at the 

 fame time, how little certainty fuch ex- 

 ternal marks afford in a true diftinclion 

 of things. This fait is therefore very 

 often confounded with the fal jnirabile* 



SECT. CXXXVIII. 



3. Saturated with mineral acids, Alcali 

 falls communis acidis mineralibus ad fatiiri- 

 tatem mixtum. Neutral falts, Salia media, 

 folia neutra. 



a. With the acid of fea-falt, common fait, 

 fea-falt, Sal commune. Seel, exxix. 



b. With the vitriolic acid, Sal mirabile. 

 Sefa exxvi. 



SECT. 



