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Licensed for the sole use of the purchaser.See license agreement penalties for distribution. PAGE 2 COMPRESSED GAS AssociAT1oN INC. CGA G-1.5-2015 3.2.5 Semisolid (paste) Carbide lime and water mixtures containing in excess of 45% solids. 3.2.6 Slaking Adding water to convert calcium oxide to calcium hydroxide. 3.2.7 Slurry Carbide lime and water mixtures containing 10%to 459/c solids. 4 Production Carbide lime is obtained from the reaction of water and calcium carbide in the generation of acetylene gas. It is also referred to as carbide slurry, generator slurry, lime slurry, and lime hydrate. Carbide lime is available wherever acetylene is produced from calcium carbide. The calcium carbide used for the generation of acety- lene is manufactured by the reaction of high quality quicklime with carbon of selected cokes at high tempera- ture in a submerged arc electric furnace. Acetylene (C2H2) is produced by reacting calcium carbide with water in specially designed acetylene generating equipment. The chemical equation for this reaction is: CaC2+2H2O —>C2H2+Ca(OH)2+ HEAT 4.1 Wet process In a wet process acetylene generator, calcium carbide is reacted with a large excess of water producing fine particles of totally slaked calcium hydroxide in a slurry form of 10%to 15%solids. 4.2 Dry process In the dry process, only a slight excess of water over the stoichiometric requirement for the reaction is added. The carbide lime is produced at approximately 99% solids. 5 Properties of carbide lime Carbide lime has slight variations in chemical analysis depending on the carbide source and the production conditions. As it comes from the generator, carbide lime has a grayish color and a characteristic odor. The grayish color is due to the presence of small amounts of finely divided carbon and ferrosilicon. The odor, com- posed of acetylenic impurities, dissipates quickly on exposure to air. The pH of a saturated solution of calcium hydroxide is temperature dependent. Measured at 77 °F (25 'C), as specified in Environmental Protection Agency (EPA) test method 904513, the pH is 12.454. See Federal Register, Vol. 60, No. 64 as well as Stand- ardization of pH Measurements by Richard A. Durst. [2, 3].2 Carbide lime is only slightly soluble in water, less than 0,2% by weight at room temperature. 5.1 Bulk density versus percent solids Table 1 shows the typical weight ratio and density data for carbide lime at various solids content based on a specific gravity of solids of 2.14. Table 1—Bulk density versus percent solids Solids content Weight ratio Density Ib carbide lime! Ibt gal (kgIL) Ib available CaO 10 144 8.8(1.05) 20 7.3 9.3(l.11) 30 4.8 40 3.6 10.6(1.27) 50 2.9 11.4(l.37) 60 2.4 12.3(l.4 z The presence of calcium carbonate(CaCO3)or an excess of soluble calcium salts,which form Ca"ions in solution,would suppress the pH of the solution to values lower than that of a saturated solution of Ca(OH)z. This document licensed for the sole use of the purchaser It may not be shared with any other person or used after the expiration date without the express written permission of the C.GA, Any unauthorized use, reproduction, distribution, or modification of this printed page will result in a$5,000 liquidated damages fee plus loss of access to CGA publications for one year for your company.