248,886. Cozens, A. A., and Gas Light & Coke Co. Jan. 28, 1925. Incrustation, removing.-In breaking down and clearing hard calcareous &c. materials such as water-laid deposits, the material is treated with free citric acid solution until softened or until a readily removable sludge-like mass is produced. A solution of 10-20 per cent strength is usually employed. Heat may be applied either initially or for the whole period of treatment to accelerate the action but the temperature is preferably maintained below the boiling point. Roughly crushed fruit may be used as the source of citric acid; also a small proportion, e.g. 2.3 per cent of an alkali chloride such as common salt may be added. In an example, a solution containing 30 per cent of citric acid and 2.25 per cent of sodium chloride was introduced into a boiler and heated up to 140‹ F. which was maintained for 30 minutes by which time the deposit was reduced to the condition of a soft sludge. The boiler was then flushed out with water. Specifications 10771/91, [Class 123, Steam generators]; and 191,449 are referred to.
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