s¥6 OF QUICK-LIME

place on adding the alkali, drop more,—and more, till no turbidnefs arifes:—then filtre -the whole: abforbent earth, that is not calcareous; for acids attract volatile alkali more ftrongly

what remains in the filtre, is

than any of the abforbent earths, except the calcareous clafs alone. S22; It may oftener happen, that a confider- able proportion of gyp/um may be united vith lime-ftone in the fame quarry; and as this fubftance would greatly alter the na- ture of the lime as a cement(fee p. 449) and would probably affe@ it as much as a manure, it is of more importance to inform the reader of the eafieft way of difcovering this fubftance when it is prefent in lime- {tone.| It has been already faid, that gyp/um is a compound, confifting of the vitriolic acid and calcareous earth; and as the vitriolic acid attracts this earth more ftrongly than any of the other acids, this compofition isnot

in the leaft affected by either the nitrous or

muriatic acids. Hence it follows, that if gyp/um‘hall be containéd in any calcareous mafs ex- amined