Calcium chloride is the only compound of practical importance used as an admixture in Portland cement to accelerate the setting process;The present conception of the constitution of Portland cement clinker is best given in the work of Dr. Hans Kuhl representing the German idea and the work of Brounmiller and Bogue representing the American view;Methods are given for the preparation of tricalcium silicate, tricalcium aluminate, beta dicalcium silicate and gamma dicalcium silicate;The rate of hydrolysis of the constituents of cement were studied by the electrometric method;The results of the studies on the concentrated calcium hydroxide solutions showed that small amounts of calcium chloride accelerated the rate of hydrolysis of the tricalcium aluminate and tricalcium silicate, but retarded the hydrolysis of beta dicalcium silicate and gamma dicalcium silicate;In solutions not saturated with calcium hydroxide, calcium chloride retarded the rate of hydrolysis of all the compounds studied;The data show that calcium chloride combines with calcium hydroxide;The action of calcium chloride in the setting processes of cement is explained by the theories of L. Forsen and Hans Kuhl.