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Stone (ARTIFICIAL Most varieties)

ARTIFICIAL. Most varieties of artificial stone (using the term in a restricted sense, excluding brick and terra-cotta) have a base of hydraulic mortar, with which sand and pulverized stone of different kinds are mixed. Mr.

Ransome of Ipswich, England, introduced a kind of artificial stone in which siliceous instead of calcareous matter was employed as the cementing material. The process at present followed in the manufacture of this artificial stone consists in carefully mixing well-dried sand and dust of chalk with silicate of soda, obtained by digesting flints under pressure in a boiling solution of caustic soda. After molding, the blocks are exposed to the action in vacuo of chloride of calcium in a solution, where, by chemical reaction, the block is transformed into a silicate of lime, a body of unusual strength and durability. other compound formed is chloride of sodium, or common salt, and is removed with water. The artificial stone of Sorel, a French chemist, is made by mixing a cement formed of the basic oxychloride of magnesium with sand, chalk, or powdered marble. The coment, which may be molded of itself into a hard stone, is procured by acting on protoxide of magnesium (calcined and ground carbonate of magnesia or magnesite) with a concentrated solution of chloride of magnesium.

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