| abstract |
Finely dispersed solids contained in an aqueous liquid of pH above 4 are flocculated by addition of 0,0005 to 0,5% by weight/weight of solid of a water-soluble copolymer of acrylic acid or the alkali-metal or ammonium salt thereof and acrylamide. The acrylamide units must comprise from 45 to 75 weight per cent. of the copolymer molecule. Other flocculents may also be used in conjunction with the polymer, e.g. ferrous sulphate, ferric chloride, chlorinated ferrous sulphate, crude aluminium sulphate, sodium aluminate, aluminium sulphate and calcium hydroxide. Specification 768,662 is referred to. |