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PURPOSE:To manufacture copper pyrophosphate crystals having a large grain size, a low water content and a high apparent specific gravity by adding sodium hydroxide and an alkali pyrophosphate to an aqueous copper salt soln. contg. an acid and by carring out a double decomposition reaction. CONSTITUTION:Water or separated motor liquor is charged into a reactor 1 provided with a pH meter 7, a thermometer 8 and a stirrer 9, and it is heated to about 50 deg.C. A copper chloride soln. contg. an acid such as hydrochloric acid, an aqueous sodium hydroxide soln. and a potassium pyrophosphate soln. are fed successively or continuously from feed pipes 4, 5, 6, respectively while keeping the equv. ratio of Cu/P2O7 at about 1. They are continuously reacted at about 50 deg.C and about 3.5-4.0pH for about 2hr residence time. The liq. reaction product is drawn out from a pipe 10 and separated into coarse crystals and mother liquor with a crystal-mother liquor separator 2. Tbe mother liquor is discharged into a mother liquor vessel 3. The resulting coarse crystals are dried at about 80 deg.C for about 2hr to obtain dried copper pyrophosphate. |
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