324. Calcium Phoflphate, Ca3(P04)2. — While carbonate of
lime is the mineral out of which all shells are made, the
phosphate of calcium, mixed with very small quantities of
the carbonate and sulphate and fluoride, forms the mineral
portion of bones. It is estimated that the amount of phos-
phorus contained in this salt in the bones of a full-grown
man is from 500 to 800 grammes. Phosphorus is obtained
from bones, and the process is described in § 253. As phos-
phate of lime exists so largely in animals, it is necessary
that it be provided for them in the food that they eat.
Accordingly it is present in all cereal grains, in leguminous
plants, and many other vegetables, the soil of course fur-
nishing it to them. It is not only, then, the animal sub-
stance in bones, the gelatine, that makes them a good ma-
nure; but the mineral part is of essential service, to some
crops especially, if the soil be at all deficient in phosphate
of lime.
Calcium phosphate occurs abundantly also in the min-
eral kingdom, as you will leara more particularly in the
study of Mineralogy, Part IIL



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234 CHBHISTBT.
GBOUP III. ALUMINIUM (eTC). — GROUP IV. MAGNESIUM
AND ZINC.
