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:—

Saponification Equivalent.Acidity (as Oleic Acid) Per Cent.Titre, °C.Refractive Index at 60° C.
2860.537.51.4542

Lard should absorb 59 to 63 per cent. iodine.

Cocoa-nut Oil.—The best known qualities are Cochin and Ceylon oils, which are prepared in Cochin (Malabar) or the Philippine Islands and Ceylon respectively.

The dried kernels of the cocoa-nut are exported to various ports in Europe, and the oil obtained comes on the market as Continental Coprah Oil, with the prefix of the particular country or port where it has been crushed, e.g., Belgian, French and Marseilles Coprah Oil. Coprah is also imported into England, and the oil expressed from it is termed English Pressed Coprah.

The following are typical examples from bulk:—

Saponification Equivalent.Acidity (as Oleic Acid) Per Cent.Titre, °C.Refractive Index at 25° C.
Cochin oil 215.5 1.5 23.5 1.4540
Cochin oil 214.3 2.6 22.1 1.4541
Ceylon oil 214.6 5.47 23 1.4535
Ceylon oil 216 3.95 22.75 1.4535
Belgian coprah 214.2 1.65 23 1.4541
Belgian coprah 215 2.60 22.1 1.4540
French coprah 214.2 6.55 23 1.4535
French coprah 214.8 7.42 22 1.4540
Pressed coprah 215.8 7.45 22.2 1.4542
Pressed coprah 216 9.41 22 1.4555

Cocoa-nut oil should absorb 8.9 to 9.3 per cent. iodine.

Palm-nut Oil.—The kernels of the palm-tree fruit are exported from the west coast of Africa to Europe, and this oil obtained from them. Typical samples of English and Hamburg oils tested:—

Saponification Equivalent.Acidity (as Oleic Acid) Per Cent.Titre, °C.Refractive Index at 25° C.
225 4.4 24 1.4553
227 7.7 23.8 1.4553

Palm-nut oil should absorb 10 to 13 per cent. iodine.

Olive Oil.—The olive is extensively grown in Southern Europe and in portions of Asia and Africa bordering the Mediterranean Sea. The fruit of this tree yields the oil.

The free fatty acid content of olive oil varies very considerably. Very fine oils contain less than 1 per cent. acidity; commercial oils may be graded according to their free acidity, e.g., under 5 per cent., under 10 per cent., etc., and it entirely depends upon the desired price of the resultant soap as to what grade would be used. The following is a typical sample for use in the production of high-class toilet soap:—

Saponification Equivalent.Acidity (as Oleic Acid) Per Cent.Titre, °C.Refractive Index at 15° C.
288 1.8 21 1.4704

Olive oil should absorb 80 to 83 per cent. iodine.

Olive-kernel oil, more correctly termed Sulphur olive oil.

The amount of free fatty acids is always high and ranges from 40-70 per cent., and, of course, its glycerol content is proportionately variable. The free acidity increases very rapidly, and is, doubtless, due to the decomposition of the neutral oil by the action of hydrolytic ferment.

A representative sample of a parcel tested:—

Saponification Equivalent. Acidity (as Oleic Acid) Per Cent. Refractive Index at 20° C.
298 40.96 1.4666

Palm oil is produced from the fruit of palm trees, which abound along the west coast of Africa. Lagos is the best quality, whilst Camaroons, Bonny, Old Calabar and New Calabar oils are in good request for bleaching purposes.

Analysis of typical samples of crude palm oil has given:—

Saponification Equivalent. Acidity (as Oleic Acid) Per Cent. Titre, °C. Water and Impurities, Per Cent.
278 10.7 45 1.6
280 31.2 44.5 2.8

Palm oil should absorb 51 to 56 per cent. iodine.

In the lower qualities we have examples of the result of hydrolytic decomposition by enzymes, the free acidity often amounting to 70 per cent.

Cotton-seed Oil.—This oil is expressed from the seeds separated from the "wool" of the various kinds of cotton tree largely cultivated in America and Egypt.

In its crude state cotton-seed oil is a dark fluid containing mucilaginous and colouring matter, and is not applicable for soap-making. The following figures are representative of well-refined cotton-seed oils:—

Specific Gravity at 15° C.Saponification Equivalent.Acidity (as Oleic Acid) Per Cent.Titre, °C.Refractive Index at 20° C.
0.92292900.2433.61.4721
0.9242990.39351.4719

Cotton-seed oil should absorb 104 to 110 per cent. iodine.

Cotton-seed Stearine.—The product obtained by pressing the deposit which separates on chilling refined cotton-seed oil.

A typical sample tested:—

Saponification Equivalent.Acidity (as Oleic Acid) Per Cent.Titre, °C.
285.10.0538

Arachis Oil.—The earth-nut or ground-nut, from which arachis oil is obtained, is extensively cultivated in North America, India and Western Africa. Large quantities are exported to Marseilles where the oil is expressed. Arachis oil enters largely into the composition of Marseilles White Soaps.

Representative samples of commercial and refined oils tested:—

Specific Gravity at 15° C. Saponification Equivalent Acidity (as Oleic Acid) Per Cent. Titre, °C. Refractive Index at 20° C.
Commercial 0.9184 298 2.6 28.6...
Refined 0.9205 285 0.22 24.0 1.4712

Arachis oil should absorb 90 to 98 per cent. iodine.

Maize Oil.—America (U.S.) produces very large quantities of maize oil.

Typical samples of crude and refined oil gave these figures:—

Specific Gravity at 15° C. Saponification Equivalent Acidity (as Oleic Acid) Per Cent. Titre, °C. Refractive Index at 20° C.
Crude 0.9246 294 1.41 15 ...
Refined 0.9248 294.1 0.40 17.2 1.4766

Maize oil should absorb 120 to 128 per cent. iodine.

Sesame Oil.—Sesame oil is very largely pressed in Southern France from the seeds of the sesame plant which is cultivated in the Levant, India, Japan and Western Africa.

A fairly representative sample of French expressed oil tested:—

Specific Gravity at 15° C. Saponification Equivalent Acidity (as Oleic Acid) Per Cent. Titre, °C. Refractive Index at 20° C.
0.9227 295.2 1.84 22.8 1.4731

Sesame oil should absorb 108 to 110 per cent. iodine.

Linseed Oil.—Russia, India, and Argentine Republic are the principal countries which extensively grow the flax plant, from the seeds of which linseed oil is pressed. It is used to a limited extent in soft-soap making.

A good sample gave on analysis:—

Specific Gravity at 15° C. Saponification Equivalent Acidity (as Oleic Acid) Per Cent. Titre, °C. Refractive Index at 15° C.
0.935 292 1.2 20 1.4840

Linseed oil should absorb 170 to 180 per cent. iodine.

Hemp-seed oil is produced from the seeds of the hemp plant which grows in Russia. This oil is used in soft soap-making, more particularly on the Continent.

A typical sample gave the following figures:—

Specific Gravity at 15° C. Saponification Equivalent. Titre, °C. Iodine No.
0.926 292.6 15.8 143

Sunflower oil is produced largely in Russia.

A specimen tested:—

Specific Gravity at 15° C. Saponification Equivalent. Acidity (as Oleic Acid) Per Cent. Titre, °C. Iodine No.
0.9259 290.7 0.81 17 126.2

Castor Oil.—The castor oil plant is really a native of India, but it is also cultivated in the United States (Illinois) and Egypt.

A typical commercial sample tested:—

Saponification Equivalent. Acidity (as Oleic Acid) Per Cent. Titre, °C. Iodine No. Optical Rotation αD Refractive Index at 25° C.
310 1.5 2.8 84.1 + 4° 50' 1.4787

Fish and Marine Animal Oils.—Various oils of this class have, until recently, entered largely into the composition of soft soaps, but a demand has now arisen for soft soaps made from vegetable oils.

We quote a few typical analyses of these oils:—

Specific Gravity at 15° C.Saponification Equivalent. Acidity (as Oleic Acid) Per Cent. Titre, °C.Unsaponifiable Matter Per Cent.
Pale seal oil 0.9252 289 0.947 15.5 0.8
Straw seal oil 0.9231 288 4.77 15.8 1.2
Brown seal oil 0.9253 291 16.38 16.2 1.9
Whale oil 0.9163 297 1.49 16.1 1.8
Dark whale oil 0.9284 303 12.60 21.8 2.4
Japan fish oil 0.9336 296 4.79 26 0.67
Japan fish oil 0.9325 302 10.43 28 1.55
Brown cod oil 0.9260 313 14.91 21.8 1.9
Pure herring oil 0.9353 288 11.39 21.6 1.5
Kipper oil 0.9271 297 5.14 22.7 3.25

Waste Fats.—Under this classification may be included marrow fat, skin greases, bone fats, animal grease, melted stuff from hotel and restaurant refuse, and similar fatty products. The following is a fair typical selection:—

Saponification Equivalent. Acidity (as Oleic Acid) Per Cent. Titre, °C.
Marrow fat 283.3 3.6 38.7
White skin grease 287.2 4.3 36.4
Pale skin grease 286.3 9.87 35.7
Pale bone fat 289.7 8.8 40.7
Brown bone fat 289.1 11.0 41
Brown bone fat 292 20.5 40.2
Animal grease 289.4 38.1 40.4
Melted stuff 286.3 12.8 37.7

The materials in the above class require to be carefully examined for the presence of unsaponifiable matter, lime salts and other impurities.

Fatty Acids.—We have already described the various methods of liberating fatty acids by hydrolysis or saponification.

Under this heading should also be included stearines produced by submitting distilled fat to hydraulic pressure, the distillates from e from unsaponifiable matter, cocoa-nut oleine, a bye-product from the manufacture of edible cocoa-nut butter and consisting largely of free acids, and palm-nut oleine obtained in a similar manner from palm-nut oil.

These are all available for soap-making.