Transparent soap is prepared by drying ordinary soap, dissolving it in alcohol, allowing the solution to remain at rest so long as any impurities are precipitated, decanting off the alcoholic liquid and evaporating it until it is of such a consistency as to solidify when cooled in metallic molds. Many kinds of transparent soaps are made by the cold process, the trans parency being accomplished by the addition of sugar. Glycerine is often incorporated with transparent soaps for emollient effects, while for disinfecting purposes carbolic acid, coal tar, eucalyptus oil and other substances are added.
Mottled soaps are produced by mixing min eral coloring-matter with the soap during a certain stage of the hardening.
Medicated soaps contain antiseptics, such as carbonic acid, creosote, chloride of potash and sulphur, mixed with ingredients. A soap for the use of taxidermists in preserving skins is produced by the addition of arsenic. A large industry has developed in this country in scour ing-soaps, which are produced by the addition of fine sand or pumice-stone to the ordinary soap when in its plastic state.
Soap powders are made by mixing dry sal soda and borax with hot liquid soap, with the addition of a definite proportion of hot water, sufficient to provide the necessary water of crystallization to the soda in its subsequent change. The mixture is stirred constantly until lumps begin to form, when it is piled in trays where the soda completes its crystallization. It is then milled to powder form.
History.— The use of soap is of great an tiquity. A well-equipped soap factory was found by the excavators of Pompeii. Histori cal records of Italy and Spain show that soap was in use in those countries in the 8th century. It was known in France in the 12th century and in England in the late 14th or early 15th century. In 1622 James I granted a monopoly to a soap-maker under which he was allowed to make 3,000 tons a year, and paid $100,000 a year for the privilege. In 1711 a tax of one penny per pound was laid upon the soap pro duced by English soap-makers, and in 1816 this tax was increased to three pence per pound. In 1833 it was reduced to one and one-half pence, and this tax when abolished in 1853 was bringing annually into the British treasury a revenue of more than $5,000,000.
Soap-making in America.— In the Amer ican colonies soap-making was at first largely a household art, the housewife utilizing the fats saved from the dripping-pan to make soft soap for her own use, and also even a sort of hard soap, of a quality, however, that would not suit the housekeeper of to-day.
As early as 1608, on the second ship from England to the Jamestown colony, came a num ber of Germans and Poles, skilled craftsmen, among whom were several proficient in handling fat and soap-ashes. In 1621 soap-ashes for export to England were worth from six to eight shillings per hundredweight, and 50 years later the settlements now included in Maine and New Hampshire derived their chief wealth from soap-ashes and fat. While there were small soap-boiling establishments in nearly all the large towns by 1795, their aggregate product probably did not exceed $300,000 in value. The discovery by Nicolas Leblanc (q.v.), about 1791, of a process for manufacturing soda on a large scale was utilized some 30 years later, when chemical manufacturers and soap-makers began to avail themselves extensively of the supply of soda thus cheaply afforded.
Among the early establishments of the soap trade one of the largest was that of William Colgate of New York, founded in 1806. Fancy
soaps were at this time unknown, and the mak ers of the American product contented them selves with a very common grade of soap; but so rapid was the advance that by 1835 they were supplying nearly all the home demands and were also heavy exporters, principally to England.
About 1850 American manufacturers were employing substantially the same methods and processes that were used in England. New England was then the principal centre of the manufacture for the United States, although New York and Philadelphia were gaining prom inence. At that time filling materials were practically unknown and "settled)) soaps were merely run into the wooden frames and crutched for hours, until rendered thick from cooling, or were finished by boiling down. The material was ladled by hand from the kettles into the frames, or put into buckets or tubs and carried and emptied into the frames. The kettles themselves had cast-iron bottoms, to which a wooden curb was fastened by means of cement. The composition of this cement, which was used to prevent leakage, was re garded at that time as a great trade secret, especially when the cement was capable of pre venting the leakage for some length of time. The waste lye was run off through a pipe reaching through the wooden curb to a point near the bottom of the kettle. The kettles were heated by open fire, and the contents were kept from burning by stirring them with a long iron rod flattened at the end. The lye was made by leaching wood-ashes, since the use of caustic soda had made very slow advances.
While processes and methods were thus, comparatively speaking, at a standstill during the first four decades of the 19th century, the soap industry nevertheless steadily advanced in importance and prepared itself for the wonder ful development that immediately followed the discoveries of Chevreul. That chemist demon strated the true principles of saponification, and no later improvement, whether in the introduc tion of the steam processes or in the discoveries and uses of the many new vegetable and ani mal oils, has been of greater importance. Of the total soap produced at this time Massachu setts was credited with over one-quarter. Five years later the soap industry had grown to great proportions. The manufacture of fancy soaps had already been begun, and in 1850 was es tablished on an extensive scale. Shaving soap, always in great demand in those days, when beardless faces were the rule, was also greatly improved in this decade, and many other of the common toilet necessities of to-day were either first brought out or developed to comparative excellence at this time. Soon soap-making was facilitated by the introduction of machinery and now there are specially constructed machines designed and adapted for almost every step in the different processes of manufacture where their introduction has been of advantage. At present American soaps are strong competitors in the markets of the world, and in quality they rival the best of European production.
The introduction of sapolio marked a new era in the soap business. It was a combination of true soap and scouring substances in such proportions as to increase to the highest point the advantages of each. The Bath brick of the scullery has gone since its advent, and the prin ciple upon which sapolio was established is now utilized in many forms. See FAT TISSUE;