Yellow Soap has rosin added to the lye, aud, indeed, most laundry soaps have this ingredient, which makes better lather, and is at the same time a cheap adulterant.
Adulteration of Soaps. Consumers of soap, says a writer in the Deutsche Industrie Zietung, should not neglect to inform themselves of the real value of the wares they buy, and to prove the absence of intentional adulterations. A very old trick is to increase the weight of soap with water ; but as ordinary soap soon loses this by evaporation in the air, this deception will not suc ceed unless the soap is sold off quickly. There are two other methols of overweighting. One consists of putting in chemicals that arc adapted to hold this excess of water in the soap, so that it loses little or nothing in weight by laying. Another way is to add some mineral substances, soluble or insoluble, to increase the weight and diminish proportionally the value of the soap. Arti ficially increasing the amount of water and adulteration with worthless chemicals pays well, and some manufacturers do a fine business by duping their customers.
It is no wonder that a housekeeper does not have her toilet soap and family soap analyzed, because she uses comparatively little of it, and is satisfied if it looks good and makes a good suds. When large consumers, however, neglect to submit their soap to an examination, they may suffer considerable loss. If soap was tested oftener than it is, more frequent complaints would be made public, and better wares would result. There is soap in the market that contains 75 per cent. of water, and externally cannot be dis tinguished from soap that contains only 12 per cent. It is easy to see how great a difference there may be in the value of two specimens of the same price. By simply increasing the amount
of water, doors and gates are open for deception in soap, so that many manufacturers make a profit of a hundred per cent. by sell ing water instead of soap.
Gelatinous substances are most frequently used to retain the water in soap, and are at the same time an excellent filling. Alumina in the hydrated form performs this service best. The author detected this substance in six samples of soap, which had over 60 per cent. water, and were sold by their manufacturers at the same price as another manufacturer sold soap with 24 per cent. Other gelatinous substances, like silica, and organic sub stances, are used. They are easily detected by chipping up the soap and dissolving it in alcohol, in which they are insoluble, while pure soap is perfectly soluble. The undissolved residue may be filtered out and more carefully examined. Hot water will dissolve the gelatinous substances if they are organic, like gelatine or glue, leaving alumina, silica, etc., unaffected. By evaporating the aqueous solution and weighing the residue, the quantity of gelatine can be determined. The silica and alumina can be dried, then ignited in a platinum or porcelain crucible and weighed.
Waterglass is frequently added to soap, and, although it is not arr injurious ingredient, such soap can be made cheaper, and should be sold as waterglass soap. In some samples the author found starch, gypsum, chalk, clay, phosphate of lime (bone ash), and barytes, or blanc fire, as the adulterants. All these can be sepa rated by dissolving the dry soap in alcohol. The alcoholic solu tion may be evaporated to dryness, dried at 212° Fahr., and weighed.