hardness of water

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hardness of water Reluctance of water to produce a lather with soap, due to various dissolved salts, mainly those of calcium and magnesium. These salts give rise to an insoluble precipitate, which causes ‘fur’ or ‘scale’ in boilers, pipes and kettles. Lather is inhibited until all the dissolved salts are precipitated as scum, which floats on the surface. Hardness may be temporary (removed by boiling), caused by calcium bicarbonate; or permanent (not affected by boiling), caused by calcium sulphate.