Page 184 - Chemical and process design handbook

Speight_Part II_C 11/7/01 3:08 PM Page 2.125

CALCIUM CARBONATE 2.125
and for chicken grit. Marble dust is employed in abrasives and in soaps.
Crude, pulverized limestone is used in agriculture to sweeten soils, and
pulverized arid levigated limestone is used to replace imported chalk
and whiting.
Whiting is pure, finely divided calcium carbonate prepared by wet grind-
ing and levigating natural chalk. Whiting mixed with 18% boiled linseed oil
yields putty, which sets by oxidation and by formation of the calcium salt.
Much whiting is consumed in the ceramic industry. Precipitated, or artificial,
whiting arises through precipitation, e.g., from reacting a boiling solution of
calcium chloride with a boiling solution of sodium carbonate or passing car-
bon dioxide into a milk-of-lime suspension. Most of the latter form is used
in the paint, rubber, pharmaceutical, and paper industries.