Argillaceous Earth. 7, 



lime it Is brought into fufion by borax or. 

 microcofmic fait, but is fcarcely affe&ed by 

 fixed alkalis, or calces of lead. 



Argillaceous Earth or Earth of Alum. 



i ft * This may more conveniently be called, 

 Argill, its fpeeific gravity when pure does not 

 exceed 2,000. ^ 



2*' It is exceedingly diffufible, but fcarcely 

 more foluble in water than pure magnefia. 



3 d * It is combinable with acids, and when 

 combined with the nitrous or marine, like 

 magnefia it is feparable, but fcarcely precipitable 

 by the vitriolic acid * with which it forms 

 Alum, which always contains an excefs of 

 acid and has an aftringent tafte ; when com- 

 bined with any of thefe acids, it is not pre- 

 cipitable by the acid of fugar, which diftin- 

 quifhes it from the foregoing Earths, all 

 of which (except the ponderous united to the 

 vitriolic acid) are precipitable from the vitrio- 

 lic, nitrous and marine acids, by that of fugar, 

 though the precipitation is not always appa- 

 rent before the liquors are evaporated, nor at 

 all, if there be an excefs of the mineral acids. 



* For if concentrated oil of vitriol be dropect into a very 

 fatnrate folution of nitrous or marine Alum, a grey ifh preci- 

 pitate w$l immediately appear. 



64 The 



