2 Of Salts fimple and compound. [Book VL 



ing of mineral fubftances naturalifts have generally 

 clafied them under four principal heads, falts, earths, 

 metals, and inflammables. Perhaps modern philofo- 

 phers might adopt an arrangement more confiftent 

 with recent difcoveries;' yet novelty in clafiification 

 but feldom facilitates the labour of the ftudent, and 

 it is commonly fafeft to follow a beaten track in 

 Jcience, unlefs it leads to error. 



Thole fubftances are denominated falts which are 

 fu-fible, volatile, foluble * in water, not inflammable, 

 and fapid when applied to the tongue. The mod 

 fimple ftate of falts, is a mafs, white, brittle, and in 

 forne degree tranfparent. Salts in certain degrees of 

 heat are fluid and tranfparent, like oi-L They differ 

 in their degree of fufibilky and volatility. Some af- 

 fume the form of vapour in the ordinary temperature 

 of the atmofphere, others in a great degree of heat 

 remain fixed f . Previous to treating of the particular 

 fubftances of this clafs, it will be proper to make a 

 few obfervations on the formation of falts in general. 

 Salts are either fimple or compound. Simple falts 

 are diftinguifhed into alkalis and acids; and from the 

 union of an acid and an alkali are produced compound 

 falts, which are alfo called neutral, becaufe by this 



* The diftin&ion between folution and mixture has been already 

 ftated; but it may not be improper to remind the reader, that in 

 folution the body which was folid is fo completely in union uith 

 the fluid or rrienftruum, that the compound is completely tranfpa- 

 rent, though not always colourlefs. Common fait, for inftance, 

 with water, makes a colourlefs foiution; but blue or green vitriol 

 makes a blue or green folution with water. A mixture on the 

 contrary is always muddy, and if left to ftand, a fediment will be 

 tlepofited. The point of Saturation is when the fluid will hold no 

 more of the folid body in clear folution, bun precipitates it, or lets 

 it fall to the bottom. 



f Not volatile, or rifing in vapour. 



combination 



