GB665455A - Improvements in or relating to water treating compositions - Google Patents

Abstract

A composition for treating water comprises a substantially homogenous mixture of (a) 80-96 per cent by weight of a watersoluble molecularly-dehydrated alkali metal phosphate having a ratio of alkali metal oxide to P2O5 of from 1.0 to 1.3;(b) [a] 19.98-2 per cent by weight of an alkali metal carbonate, bicarbonate or percarbonate or a mixture thereof and (c) 0.01-2 per cent by weight of an amine of the formula R1-NH-R2 in which R1 is hydrogen or an aliphatic or alicyclic hydrocarbon radical and R2 is an aliphatic or alicyclic hydrocarbon radical, at least one of the radicals containing not less than 6 nor more than 10 carbon atoms. Examples of amines are hexylamine, heptylamine, octylamine, decylamine, cyclohexylamine and dicyclohexylamine, of which p heptylamine is preferred. The percentage of phosphate in the composition is preferably not less than 88 per cent and the percentage of carbonate or the like is preferably from 10 per cent to 3.98 per cent. In one example a commercial sodium hexametaphosphate product is mixed with 6 per cent by weight of sodium carbonate and 0.01 per cent by weight of heptylamine is blended with the resulting mixture. In another example sodium septaphosphate (Na9P7O22) is mixed with 6 per cent of sodium carbonate and 1 per cent of heptylamine is blended with the mixture. When the composition contains an alkali metal carbonate, bicarbonate or a mixture thereof the ingredients of the composition must be so proportioned as to yield a pH in 1 per cent aqueous solution of 6.7 to 8.0, preferably 7.8. Other preferred types of amines include: secondary alkylamines in which each alkyl group has from 6 to 10 carbon atoms and alicyclic secondary amines in which each alicyclic group has from 6 to 10 carbon atoms. Additional alkalinity-adjusting agents may be added to the composition, such as caustic soda, sodium sulphate, bisulphate or bisulphite, sodium metasilicate, trisodium orthophosphates, sodium pyrophosphates such as tetrasodium pyrophosphate and sodium acid pyrophosphate, sodium polyphosphates having a Na2O/P2O5 molecular ratio above 1.3 and mixtures of these, and also the corresponding potassium salts. The particle size of the main phosphate part of the composition should be not coarser than 50 (preferably 100) mesh.