PROCESS FOR MANUFACTURE OF LEAD CROWNS Russian patent published in 1994 - IPC

FIELD: chemistry; processes for manufacturing lead crowns from chrome-containing waste. SUBSTANCE: this process prescribes using eluate treated with ice-cold acetic acid until excessive alkaline is completely neutralized after completion of cycle of sorption-desorption of wash water used in electroplating, conducting desorption step with use of aqueous solution containing either caustic soda or sodium hydroxide plus sodium chloride, precipitating thus treated eluate using lead acetate solution heated to temperature of 40 to 60 C, agitating eluate to obtain concentration of solid product of 690 g/cu. dm, filtering off, washing and drying resultant precipitate. Thus produced crown includes 43 % lead oxide and 57 % PbCrO₄. Density: 6.0 g/cu. cm. Aqueous suspension pH value: 8.5. Thus prepared pigment has following color characteristics at λ = 593: X = 37.83, Y = 2869, and Z = 9.58. EFFECT: higher quality. 4 cl