CALCAREOUS COMPOUNDS. 
121 
fold in the ſhops. Dilute it with twice or thrice as much water, and 
keep it for use. Weigh the marle exactly, and also the quantity of 
acid which is to be poured on it, taking care that it be more than 
enough for difsolving all the calcareous matter. When the solution 
is over, after repeated agitation without more effervescence, weigh 
the whole ; the weight lost is two-fifths of the weight of the calcareous 
matter. 
Should we attempt to meaſure this by solution and precipitation, 
we are led into a number of examinations which will puzzle even an 
experienced chemist. 
And having now finiſhed the chemical history of the calcareous 
earth and magneſia, I muſt take notice of ſome compounds produced 
by nature, in which the calcareous earth is combined with acids, and 
which are worthy of your attention. 
CALCAREOUS EARTHS COMBINED WITH ACIDS. 
Theſe compounds are, 1/t, Gypsum, or the ſulphat of lime. 2dly, 
Fluor, or the fluat of lime, which is formed by a very peculiar acid 
not yet described. 3dly, Phoſphat of lime, which contains another 
peculiar acid not yet described. 4tbly, Borat of lime, but lately dis 
covered, which contains the sedative salt ; or boracic acid, combined 
with lime and with magneſia. 
1.— Gypsum. 
GYPSUM, the most abundant of thefe calcareous compounds, was 
formerly considered as a peculiar species of earth; but now we are 
better acquainted with its nature, and are well afsured that it is a com 
pound of the calcareous earth with the sulphuric acid ; or is, in the 
new language, a SULPHAT oF LIME. 
This compound is found in nature under several forms, or in seve 
ral ſtates. The greatest part is found in the form of stony masses, 
VoL. II.