Soaps Remelted

After about 3 hours or after analysis has indicated that the peroxide has been consumed (Note 5), the formic acid is removed by distillation under reduced pressure (b.p. 50°/125 mm.) in a stream of gas (carbon dioxide or nitrogen) to prevent bumping (Note 6). The residue in the flask, which consists of hydroxy-formoxystearic acids, is heated for 1 hour at 100° with an excess of 3N aqueous sodium hydroxide, and the hot, amber-colored soap solution is cautiously poured into an excess of 3N hydrochloric acid with stirring. The oil which separates is allowed to solidify, and the aqueous layer is discarded. The tan-colored solid is remelted on the steam bath by addition of hot water and stirred well to remove residual salts and water-soluble acids (Note 7). When the oil has solidified, the aqueous layer is discarded, and the solid is broken into small pieces and dissolved in 400 ml. of 95% ethanol by heating on the steam bath. After crystallization at 0° for several hours, the product is collected on a filter and dried under vacuum. The yield of crude 9,10-dihy-droxystearic acid is 75-80 g., m.p. 85-90°. After a second recrystallization from 250 ml. of 95% ethanol, the product weighs about 60-65 g. and melts at about 90-92°. A third recrystallization may be necessary to produce a pure product melting at 94-95°. The over-all yield is 55-60 g. (50-55%, based on the available oleic acid) (Note 8). 

To determine the Quantity of Sesin in Soaps,— Mr. Sutherland recommends the following process, which is said to give very satisfactory results —300 grains of soap cut into small pieces are introduced into a capsule and covered with concentrated hydrochloric acid, the contents are gently boiled till the soap is dissolved and entirely decomposed 4 ounces of hot water are added, and the capsule is set aside to cool. When cold, the cake of fatty acids and resin is removed and washed several times with warm water. After cooling it is dried and gently remelted, and kept for a few minutes at 212 to evaporate aU traces of water. 

Palm-oil soap often forms the basis for yellow and l)rown toilet soaps of this class. The old-fashimuKl ilrowa Wimlsor soap was originally a curd soap that with ag( ami fre qutmt renudting liad acquired a brown tint by oxidation of the fatty acids- -tlu of toner remelted the better the resultant soap. 

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