ON THE ADULTERATION OF SOAPby@scientificamerican


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The importance of soap as an indispensable article in the household has not restrained the adulterators from making it a favorite object of their operations, and at the present day soap is only very rarely what it should be, the alkaline salt of a fatty acid with about 15 per cent. of water, which may be increased in case of soft soaps to 30 per cent. at most. The amount of moisture is an immediate signal for adulteration. Of all substances that can be used to adulterate soap, water is of course the cheapest, and as it is also harmless, this was the first point where manufacturers made use of their knowledge. The percentage of water was raised to 26 or 28 per cent., and now nearly all the ordinary soaps contain that amount when they leave the factory. At first the retailers objected to this method, because they had to suffer the loss so far as it dried out and lost weight in the store. The next point was to find some substance that would prevent this rapid drying, and it was very soon discovered that those soaps that contained an excess of lye retained moisture longer. Henceforth it was only necessary to use lyes of extra strength so as to obtain a large yield of soap containing an excess of water. The results of this ingenious method are before us; in the shops of the soap dealers the bars of soap become coated with a crust of white crystals, which is nothing but soda. If a few drops of corrosive sublimate be dropped on these crystals, a red spot will at once be produced by the formation of mercuric oxide. In addition to the deception of the public who buy such soaps, this alkali destroys clothes washed with it, as the fiber of the tissues is directly attacked by it, while the proper action of the soap depends on its enveloping the particles of dirt and carrying them off. Soap is subject to another kind of adulteration called filling, or weighting. Soapstone and similar mineral substances are added to the finished soap to increase its weight. But it may be added that this fraudulent weighting is rare. Large establishments cannot take the risk of being detected in such avaricious practices, and small ones scarcely have the apparatus at their disposal for making a uniform mixture which will not arouse suspicion.
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