Analyfis of Earths and Stones. 167 



100 gr. of the foliation, gives that contained in 

 the whole folution, by the rule of proportion, 

 from which the ponderous Earth, if any be 

 found in fubfequent experiments, is to be 

 deduted. 



The quantity of iron being thus found, 

 the remainder of the folution is to be preci- 

 pitated by aerated mineral alkali, and then 

 boiled for half an hour to expel a$ much as 

 poffible of the fixed air; by this means 

 the whole of its contents are precipi- 

 tated, and nothing remains in folution, but 

 cubic nitre and a little common fait ; when 

 the precipitate has fettled after one or two 

 days reft, the liquor is to be poured off, and 

 the laft portions taken up with a glafs fyringe. 

 Diftilled water is then to be added to the 

 precipitate and boiled over it, and afterwards 

 poured off and t^ken up uruil it comes of 

 taftlefs. 



The precipitate being fufficiently dried, is 

 to be re-diffolved in nitrous acid twice, and 

 evaporated to drynefs, then calcined for 

 one hour in a white heat, and laftly treated 

 with about fix or eight times its weight of 

 diflilled vinegar, in a heat of about 60 de- 

 grees, for one or two hours ; by this means 

 the ponderous, calcareous, and magnefia 

 Earths will be extracted and feparated from 



M 4 the 



