M 1NERALOGY. '14$ 



7. Fall to powder in the air, which is 

 effected by nothing elfe, than that 

 they eafily lofe their humidity. 



8. Mixed with the vitriolic acid, it 

 makes the fal mirabile. 



9. It melts eafier, and is fitter for pro- 

 ducing the fal commune regenerating 



nitrum cubic:im, &c. Perhaps it is 

 alfo more conveniently applied in the 

 preparation of feveral medicines. 

 10. It is fomewhat volatile in the fire*. 



SECT. CXXXVII. 



2. Mixed with afmall quantity of the cal- 

 careous earth, Ale all falls communis terras 

 calcarcsc parcel portione comblnatum. A~ 

 pbronitrum. 



* This fait is not met with pure in Europe, but it is faid 

 to be found in both, the Indies, not only in great quantity, but 

 iikewiie of a tolerable purity • it is there collected in form of 

 an cfHorefcence in theextenfive deferts, a prr.fi '-able trade being 

 carried on in it for the making of foap and gtaTs : and there- 

 fore it is very probable, that the antients meant this fait by 

 their natron, or Baurach. The calcareous earth is fufpecled 

 either to contain tnis fait in irs own compofition, or elfe to be 

 able to generate it from itfelf : but this hypothesis cani)Ot be 

 demonilrated. It is more probable, that the heat of the fun 

 under the equator, and in the countries on b^»th fides oi it r 

 evaporates the humidity, and afterwards expels the acid out of 

 fome common fait, which either is na urahy mixed with the 

 earth, or elfe has been depofited there through tne means of 

 certain decayed ve^eublts, that always auract thi^ '"alt ; be- 

 caufe an earth from Paleiline, which Dr. rfoffoiqu' ft Come v^ars 

 ago fent to Sweden, as a matrix of the natron, did upon trial 

 yield nothing bur a common fait: and it might, perhap.s, have 

 been taken at fuch a great depth, that it had not yet fuffered 

 any de:ompofition. But this mattjr wants to be more iiiuf- 

 trated by obfervations, which might be beft made in the £aft- 

 Indies, where the gre^teft quantity is to be had, and alfo by 

 Mae farther analyfcs of the fubiiance. 



This 



