Technical Paper Volume 146-163 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 Excerpt: ...crayon known as chalk is made of finely pulverized, uncalcined gypsum. Ingredients added to the gypsum include a binder, and for colored crayons a pigment. The mixture is molded into the required shape under pressure. SULPHURIC ACID. Patents have been issued covering the extraction of sulphuric acid from gypsum, but commercial success has not been attained. Among the schemes may be mentioned (1) passing steam over red-hot gypsum, it being supposed that S02, O, and S03 would be liberated, leaving CaO behind; (2) passing HC1 gas through a red-hot mixture of gypsum and coal, forming CaCl, CO, H2S, and S; and (3) subjecting molten gypsum to an electric current and an excess of free oxygen, thus forming sulphuric dioxide, which could be conveyed into lead chambers and converted into sulphuric acid in the usual way. FLUX. Gypsum is added as flux to galena concentrate in the CarmichaelBradford blast-roasting process of reducing lead ore, a process patented in the United States in 1902, but used only at a smelter in New South Wales. Gypsum is used as flux in the concentration of lead-copper matte in reverberatory furnaces in Germany. In the smelting of certain nickel ores in New Caledonia, gypsum furnishes the sulphur necessary for collecting the metal into a matte and also acts as a base to counteract and slag the siliceous gangue, The use of calcined gypsum in copper smelting is mentioned on page 40. BREWING. Ground gypsum is sometimes added to the water used for brewing, as it increases the solubility of the albuminous matter in the malt. TERRA ALBA. Terra alba is very white rock gypsum ground to pass a 200-mesh screen. It is the same as fine white land plaster. The whitest gypsum is used for making terra alba, alabaster from New Brunswick being an example. Lum...