The blocks of soap should not be stripped until quite cold throughout, and they should be allowed to stand open for a while before slabbing. When freshly cut into tablets, the soap may appear somewhat turbid, but the brightness comes with the exposure it will receive prior to stamping and wrapping.
Saponifying Mineral Oil.—This sounds somewhat incongruous, as mineral oil is entirely unsaponifiable. Most of the suggestions for this purpose consist of the incorporation of mineral oil, or mineral oil emulsified by aid of Quillaia bark, with a cocoa-nut oil soap, and in all these instances the hydrocarbon merely exists in suspension.
G. Reale (Fr. Pat. 321,510, 1902), however, proposes to heat mineral oil together with spermaceti and strong alkali, and states that he transforms the hydrocarbons into alcohols, and these, absorbing oxygen, become fatty acids, which are converted into soap by means of the alkali.
In this connection may be quoted the interesting work of Zelinsky (Russ. Phys. Chem. Ges. Zeits. Angew. Chem., 1903, 37). He obtained substances, by acting with carbon dioxide upon magnesia compounds of chlorinated fractions of petroleum, which when decomposed by dilute sulphuric acid, yielded various organic acids. One of these acids on heating with glycerine formed tri-octin, which had the properties of a fat.
Dr. Engler, in confirmation of the theory of the animal origin of some petroleums, obtained what might be described as petroleum (for it contained almost all the hydrocarbons present in the natural mineral oil) by distilling animal fats and oils under pressure.
Electrical Production of Soap.—Attempts have been made to produce soap electrically by Messrs. Nodon, Brettonneau and Shee (Eng. Pat. 22,129, 1897), and also by Messrs. Merry and Noble (Eng. Pat. 2,372, 1900).
In the former patent, a mixture of soda-lye and fat is agitated by electricity at a temperature of 194°-212° F. (90°-100° C.), while in the latter caustic alkali is electrolytically produced from brine, and deposited on wire-netting in the presence of fat, which is thereby saponified.