378 
V,\RIETV OF SULPHATE OK LIME. 
AnalysU of 
fysiil. 
Process A. 150 grains of the pulverised stone were therefore 
boiled for some hours with 450 of subcarbonate of potash, in 
about 2000 of water. The mixture was filtred, and the 
residue washed and dried. 
B. The residue of the foregoing process, was transferred 
into dilute nitric acid, which efi'ected a partial solution, accom- 
panied with a strong effervescence. When t>o further action 
en.sued, the liquid was decanted, and the remainder w'ashed with 
water. 
C. The insoluble part (B) being in a similar manner treated 
alternately, first with subcarbonate of potash, and then with 
nitric acid, until the acid when poured on the powder, which 
had been boiled for some hours in the alkaline solution, pro- 
duced no further action, the insoluble residue w'eighed 
25,50 grains. It resisted muriatic and nitric acid, but fused 
with soda, before the blowpipe apex, into a yellowish glass. It 
therefore was silex. 
D. To ascertain whether phosphoric acid was contained in 
the nitric solution, a portion of it was assayed with nitrate of 
lead, A'c. but no vestige of this acid was discovered. 
E. All the before obtained nitric solutions, after being min- 
gled, were decomposed by the .admixtuie of subcarbonate of 
potash ; a precipitate was obtained, and this being dried, was 
covered with concentrated sulphuric acid, and heated in a pla- 
tina bason, to a dull redness. 
F. 'I’lic dry mass produced, after being levigated and digested 
in small portions of cold water, was thrown on a filtre, and 
Mills reiidne, or sulphate of lime, dried at a red heat. It ac- 
qim'ed, during this process, anofange red colour. 
^'G. The liquid obtained in process F, was decomposed by 
subcaibonate of pUiash, and yielded a white powder, which did 
not dis.solvo in potash. It weighed 4 grains after having bei n 
kept in a red hdad fur about one hour. It was magnesia- 
ii. The sulphate of lime obtained in process F, was digested 
r. ; eatedly in muriatic acid, which deprived it of colour, and 
lemlered it perfectly white, afler being washed with water. 
]. I he muriatic solution, from which the sulphate of lime 
had 
