RAW MATERIALS USED IN SOAP-MAKING.
Fats and Oils—Waste Fats—Fatty Acids—Less-known Oils and Fats of Limited Use—Various New Fats and Oils Suggested for Soap-making—Rosin—Alkali (Caustic and Carbonated)—Water—Salt—Soap-stock.
Fats and Oils.—All animal and vegetable oils and fats intended for soap-making should be as free as possible from unsaponifiable matter, of a good colour and appearance, and in a sweet, fresh condition. The unsaponifiable matter naturally present as cholesterol, or phytosterol, ranges in the various oils and fats from 0.2 to 2.0 per cent. All oils and fats contain more or less free acidity; but excess of acidity, though it may be due to the decomposition of the glyceride, and does not always denote rancidity, is undesirable in soap-making material. Rancidity of fats and oils is entirely due to oxidation, in addition to free acid, aldehydes and ketones being formed, and it has been proposed to estimate rancidity by determining the amount of these latter produced. It is scarcely necessary to observe how very important it is that the sampling of fats and oils should be efficiently performed, so that the sample submitted to the chemist may be a fairly representative average of the parcel.
In the following short description of the materials used, we give, under each heading, figures for typical samples of the qualities most suitable for soap-making.
Tallows.—Most of the imported tallow comes from America, Australia and New Zealand. South American mutton tallow is usually of good quality; South American beef tallow is possessed of a deep yellow colour and rather strong odour, but makes a bright soap of a good body and texture. North American tallows are, as a general rule, much paler in colour than those of South America, but do not compare with them in consistence. Most of the Australasian tallows are of very uniform quality and much in demand.
Great Britain produces large quantities of tallow which comes into the market as town and country tallow, or home melt. Owing to the increasing demand for edible fat, much of the rough fat is carefully selected, rendered separately, and the product sold for margarine-making. Consequently the melted tallow for soap-making is of secondary importance to the tallow melter.
The following are typical samples of tallow:—
| Saponification Equivalent. | Acidity (as Oleic Acid) Per Cent. | Titre, °C. | |
| Australian mutton | 285 | 0.85 | 45 |
| Australian mutton | 284.4 | 0.48 | 48.3 |
| Australian beef | 284.2 | 1.68 | 43.9 |
| Australian beef | 283.6 | 0.85 | 42.6 |
| Australian mixed | 285.1 | 3.52 | 44 |
| Australian mixed | 284.6 | 1.89 | 43.5 |
| South American mutton | 284.5 | 1.11 | 47 |
| South American mutton | 285 | 0.90 | 47.4 |
| South American beef | 284.7 | 0.81 | 45 |
| South American beef | 284 | 0.94 | 44 |
| North American mutton | 284.3 | 1.32 | 44 |
| North American mutton | 85 | 2.18 | 43.2 |
| North American beef, fine | 284.5 | 1.97 | 41.5 |
| North American beef, good | 283.8 | 4.30 | 42 |
| North American ordinary | 285.2 | 5.07 | 41.75 |
| North American prime city | 286 | 1.01 | 41.2 |
| Selected English mutton | 283.9 | 1.45 | 47 |
| Selected English beef | 284.2 | 2.40 | 44 |
| Home-rendered or country tallow | 284.6 | 5.1 | 43 |
| Town tallow | 285.3 | 7.4 | 42.5 |
Tallow should absorb from 39 to 44 per cent. iodine.
Lard.—Lard is largely imported into this country from the United States of America. The following is a typical sample of American hog's fat offered for soap-making:—