Cronstedt Min. § 24. Lapis hepaticus. Liver Stone.

A nucleus of this kind, taken out of a piece of alum ore from Andrarum in the province of Skone, yielded, in 100 parts, by analyſis, 33 of ſiliceous earth, 29 of cauſtic heavy earth, earth of alum about 5, and quick-lime from 3 to 7, beſides the water and vitriolic acid. By calculation it appears, that theſe baſes, together with vitriolic acid enough to ſaturate them, ought to weigh 71, which, with the addition of 33, exceeds the amount of the original 100. This increaſe points out the difference of a maſs newly chryſtallized, and of one carefully dried.

§ 91.

When we conſider that the terra ponderoſa was altogether unknown before the year 1774, and that many mineralogiſts are even now unacquainted with it, we cannot wonder that we know ſo few ſpecies of it. I have ſcarce a doubt but the terra ponderoſa aerata may be found mixed with other earths in many ſpecimens, when they come to be examined by chemical means more accurately than they could be heretofore. (See notes to §§ 58 and 88.)

CALCAREOUS EARTH,
OR
CALX.

§ 92.

As calcareous earth united to the aerial acid is found native, it requires but little trouble to have it pure. Let ſelected pieces of chalk, reduced to fine powder, be repeatedly boiled in pure water: this diſſolves any calx or magneſia ſalita which it may contain. This done, it holds no heterogeneous matter but what mechanically adheres to it, the quantity of which is generally extremely ſmall. If we deſire to be free from this likewiſe, diſſolve the waſhed chalk in diſtilled vinegar, precipitate with volatile alkaly, and after waſhing the precipitate well, dry it.

§ 93.

The ſpecific gravity of calcareous earth thus purified, is 2,720. 100 parts of it contain about 34 of aerial acid, 11 of water, and 55 of pure earth.

Acids unite with it efferveſcing, and a centenary (centenarius) excites about 22 degrees of heat. The vitriolic acid forms gypſum, difficult to diſſolve, (§ 59). The nitrous and muriatic acids form deliqueſcent ſalts (§§ 60, 61), and the acetous acid permanent chryſtals.