Fur

Fur is the term applied to the incrustation which is formed in the interior of vessels (teakettles, boilers of steam-engines, &c.) when calcareous water has been for a considerable time boiled in them. Many spring waters contain carbonate of lime held in solution by carbonic acid. When this water is boiled, the acid is expelled and the carbonate is deposited, often in association with a little sulphate, forming a lining more or less coherent upon the sides of the vessel. In steam-boilers this may be prevented by the addition of a small quantity of sal-ammoniac (ammonium chloride) to the water; carbonate of ammonia is formed and volatilised, while chloride of calcium remains in solution. This chloride, however, attacks the iron more or less according to its quantity and the other saline constituents of the water; therefore many substitutes are offered, some patented, some sold as secret preparations. The carcass of a pig that has died of disease has been found effectual. It appears to act by greasing the particles of carbonate of lime as they precipitate, and thus forming a loose and easily removable powder instead of a coherent deposit. Any other refuse fatty matter may be used for this purpose. The writer strongly recommends this simple mode of treatment, combined with frequent cleansing.