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Wash Day: Soap

SOAP AND SOAP MAKING Properties of Soap. - Garments of linen and other fabrics become soiled principally by the oily exudations of the body, as in perspiration and the natural oil of the hair, and in the case of table linen, by animal fats, etc. The skin itself, of course, retains a considerable part of the oily substances not absorbed by the clothing. These greasy substances by their adhesive quality attract and hold particles of dirt. When soap is dissolved in water, the neutral alkali salts become in part separated into alkali which dissolves, and free fatty acid which precipitates. This explains why the transparency of clear water is disturbed by the use of soap even of the purest kind.

The detergent or cleansing properties of soap are due to the presence of free alkali, either caustic potash or soda liberated in the soapsuds.

This attacks and decomposes the grease contained in soiled linen, in perspiration, and in dishwater, unites with the fatty acids, and in turn saponifies them. The process is precisely similar to that of soap-making. The union of the alkali set free in soapsuds with the grease of garments or dishwater produces a soapy substance which is readily soluble, and hence is easily removed by rinsing.