The Handbook of Soap Manufacture Part 4

CHAPTER III.

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 quant.i.ties 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:--

_______________________________________________________________________ | | | | | | | | Acidity | | | | Saponification | (as Oleic | t.i.tre, | | | Equivalent. | Acid) | C. | | | | Per Cent. | | |_________________________________|________________|___________|________| | | | | | | 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 | Acidity | t.i.tre, | Refractive | | Equivalent. | (as Oleic Acid) | C. | Index | | | Per Cent. | | at 60 C. | |________________|_________________|________|____________| | | | | | | 286 | 0.5 | 37.5 | 1.4542 | |________________|_________________|________|____________|

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 Ma.r.s.eilles 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 | Acidity | t.i.tre, | Refractive | | | Equivalent. | (as Oleic Acid) | C. | Index | | | | Per Cent. | | 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 | Acidity | t.i.tre, | Refractive | | Equivalent. | (as Oleic Acid) | C. | Index | | | Per Cent. | | 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-cla.s.s toilet soap:--

_________________________________________________________ | | | | | | Saponification | Acidity | t.i.tre, | Refractive | | Equivalent. | (as Oleic Acid) | C. | Index | | | Per Cent. | | 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 | Acidity | Refractive | | Equivalent. | (as Oleic Acid) | Index | | | Per Cent. | 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.

a.n.a.lysis of typical samples of crude palm oil has given:--

_________________________________________________________ | | | | | | Saponification | Acidity | t.i.tre, | Water and | | Equivalent. | (as Oleic Acid) | C. | Impurities, | | | Per Cent. | | 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 | Saponification | Acidity | t.i.tre, | Refractive | | Gravity | Equivalent. | (as Oleic Acid) | C. | Index | | at 15 C. | | Per Cent. | | at 20 C. | |___________|________________|_________________|________|____________| | | | | | | | 0.9229 | 290 | 0.24 | 33.6 | 1.4721 | | 0.924 | 299 | 0.39 | 35 | 1.4719 | |___________|________________|_________________|________|____________|

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 | Acidity | t.i.tre, | | Equivalent. | (as Oleic Acid) | C. | | | Per Cent. | | |________________|_________________|________| | | | | | 285.1 | 0.05 | 38 | |________________|_________________|________|

_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 quant.i.ties are exported to Ma.r.s.eilles where the oil is expressed. Arachis oil enters largely into the composition of Ma.r.s.eilles White Soaps.

Representative samples of commercial and refined oils tested:--

______________________________________________________________________ | | | | | | | | | Specific | Saponi- | Acidity | | Refractive | | | Gravity | fication | (as Oleic | t.i.tre, | Index | | | at 15 C. | Equi- | Acid) | C. | at 20 C. | | | | valent | Per Cent. | | | |____________|___________|___________|___________|________|____________| | | | | | | | | 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 quant.i.ties of maize oil.

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

______________________________________________________________________ | | | | | | | | | Specific | Saponi- | Acidity | | Refractive | | | Gravity | fication | (as Oleic | t.i.tre, | Index | | | at 15 C. | Equi- | Acid) | C. | at 20 C. | | | | valent | Per Cent. | | | |____________|___________|___________|___________|________|____________| | | | | | | | | Crude | 0.9246 | 294 | 1.41 | 15 | | | Refined | 0.9248 | 294.1 | 0.40 | 17.2 | 1.4766 | |____________|___________|___________|___________|________|____________|