Castile Soap, Spanish s., Marseilles s.; Sapo Castiliensis, Sapo Hispanicus. An olive-oil soda soap, kept both in the white and marbled state. The former is said to be the purest, the latter the strongest.
Curd Soap, made with tallow (chiefly) and soda (see above).
Medicated Soaps, containing various active ingredients. The chief of these are noticed below.
Mottled Soap, made with refuse kitchen-stuff, &c.
Soft Soap (of commerce), made with whale, seal, or cod oil, tallow, and caustic potash.
N. Gräger[172] gives the following method for the easy determination of the fat and alkali in soft (potash) soaps:—25 to 50 grammes of soap are dissolved in 150 c.c. of water by aid of heat, cooled, and mixed with an excess of salt, so that a soda-soap separates out; the latter is washed on a paper filter with a saturated solution of salt. In the filtrate the free alkali is estimated by a normal acid. The precipitate is decomposed by warming with excess of normal acid, and the quantity of acid neutralised by the combined alkali, determined by a standard soda solution. The cake of fat which separates in the last operation, is dried and weighed after adding to it, while melted, a known weight of stearin or paraffin to give it hardness.
[172] ‘Dingler’s Journal’ (‘Journ. of Chem. Soc.,’ vol. ix, new
Toilet Soaps, prepared from any of the preceding varieties, and variously coloured and scented. Formulæ are given below.
Yellow Soap, Resin soap, made with
tallow, resin, and caustic soda. Soluble glass is now largely employed in place of resin.