alkali and are therefore termed “unsaponifiable”) has been admixed fraudulently. Their amount can be determined in a direct manner by exhausting the saponified mass, after dilution with water, with ether, evaporating the latter and weighing the amount of mineral oil left behind. A few of the blubber oils, like dolphin jaw and porpoise jaw oils (used for lubricating typewriting machines), have exceedingly high saponification values owing to their containing volatile fatty acids with a small number of carbon atoms. Notable also are coco-nut and palm-nut oils, the saponification numbers of which vary from 240 to 260, and especially butter-fat, which has a saponification value of about 227. These high saponification values are due to the presence of (glycerides of) volatile fatty acids, and are of extreme usefulness to the analyst, especially in testing butter-fat for added margarine and other fats. These volatile acids are specially measured by the Reichert value (Reichert-Wollny value). To ascertain this value the volatile acids contained in 5 grammes of an oil or fat are distilled in a minutely prescribed manner, and the distilled-off acids are measured by titration with decinormal alkali. Whereas most of the oils and fats, viz. all those the saponification value of which lies at or below 195, contain practically no volatile acids, i.e. have extremely low Reichert-Wollny values, all those oils and fats having saponification values above 195 contain notable amounts of volatile fatty acids. Thus, the Reichert-Meissl value of butter-fat is 25–30, that of coco-nut oil 6–7, and of palm kernel oil about 5–6. This value is indispensable for judging the purity of a butter.
One of the most important values in oil testing is the iodine value. This indicates the percentage of iodine absorbed by an oil or fat when the latter is dissolved in chloroform or carbon tetrachloride, and treated with an accurately measured amount of free iodine supplied in the form of iodine chloride. By this means a measure is obtained of the unsaturated fatty acids contained in an oil or fat. On this value a scientific classification of all oils and fats can be based, as is shown by the above-given list of oils and fats. The unsaturated fatty acids which occur chiefly in oils and fats are oleic acid, iodine value 90·07; erucic acid, iodine value 75·15; linolic acid, iodine value 181·42; linolenic acid, iodine value 274·1; and clupanodonic acid, iodine value 367·7. Oleic acid occurs in all non-drying oils and fats, and to some extent in the semi-drying oils and fats. Linolic acid is a characteristic constituent of all semi-drying, and to some extent of all drying oils. Linolenic acid characterizes all vegetable drying oils; similarly clupanodonic acid characterizes all marine animal oils.
If one individual oil or fat is given, the iodine value alone furnishes the readiest means of finding its place in the above system, and in many cases of identifying it. Even if a mixture of several oils and fats be present, the iodine value assists greatly in the identification of the components of the mixture, and furnishes the most important key for the attacking and resolving of this not very simple problem. Thus it points the way to the application of a further method to resolve the isolated fatty acids of an oil or fat into saturated fatty acids, which do not absorb iodine, and into unsaturated fatty acids, which absorb iodine in various proportions as shown above. This separation is effected by converting the alkali soaps of the fatty acids into lead soaps and treating the latter with ether, in which the lead salts of the saturated acids are insoluble, whereas the salts of the above-named unsaturated acids are soluble. The saturated fatty acids can then be further examined, and valuable information is gained by the determination of the melting-points and by treatment with solvents. Thus some individual fatty acids, such as stearic acid and arachidic acid (which is characteristic of ground nut oil) can be identified. In the mixture of unsaturated fatty acids, by means of some more refined methods, clupanodonic acid, linolenic acid, linolic acid and oleic acid can be recognized. By combining the various methods which have been outlined here, and by the help of some further additional special methods, and by reasoning in a strictly logical manner, it is possible to resolve a mixture of two oils and fats, and even of three and four, into their components and determine approximately their quantities. The methods sketched here do not yet exhaust the armoury of the analytical chemist, but it can only be pointed out in passing that the detection of hydroxylated acids enables the analyst to ascertain the presence of castor oil, just as the isolation and determination of oxidized fatty acids enables him to differentiate blown oils from other oils.
Tests such as the Maumené test, the elaïdin test and others, which formerly were the only resource of the chemist, have been practically superseded by the foregoing methods. The viscosity test, although of considerable importance in the examination of lubricating oils, has been shown to have very little discriminative value as a general test.
Commerce.—It may be safely said of the United Kingdom that it takes the foremost position in the world as regards the extent of the oil and fat industries. An estimate made by the writer (Cantor Lectures, “Oils and Fats, their Uses and Applications,” Society of Arts, 1904, p. 795), and based on the most reliable information obtainable, led to the conclusion that the sums involved in the oil and fat trade exceeded £1,000,000 per week; in 1907 they approximated £1,250,000 per week. The great centres of the seed-oil trade (linseed, cotton-seed, rapeseed, castor-seed) are Hull, London, Liverpool, Bristol, Leith and Glasgow. Linseed is imported principally from the East Indies, Argentina, Canada, Russia and the United States; cotton-seed is chiefly supplied by Egypt and East India; rape-seed and castor-seed chiefly by East India. The importation of copra and palm kernels for the production of coco-nut oil and palm-nut oil is also considerable, but in these two cases Great Britain does not take the first place. Fish and blubber oils are principally produced in Dundee, London and Greenock. The manufacture of cod-liver oil for pharmaceutical purposes is naturally somewhat limited, as Norway, Newfoundland, and latterly also Japan, are more favourably situated as regards the supply of fresh cod, but the technical liver oils (cod oil, shark-liver oil) are produced in very large quantities in Grimsby, Hull, Aberdeen, and latterly also on the west coasts of the United Kingdom. The production of edible fats (margarine, lard compounds, and vegetable butters) has taken root in this country, and bids fair to extend largely. With regard to edible oils, edible cottonseed oil is the only table oil produced in Great Britain. The United Kingdom is also one of the largest importers of fatty materials.
Practically the whole trade in palm oil, which comes exclusively from West Africa, is confined to Liverpool, and the bulk of the tallow imported into Europe from Australasia, South America and the United States, is sold in the marts of London and Liverpool. Lard reaches Great Britain chiefly from the United States. Amongst the edible oils and fats which are largely imported, butter takes the first rank (to an amount of almost £25,000,000 per annum). This food-stuff reaches Great Britain not only from all butter-exporting countries of the continent of Europe, but in increasing quantities also from Australia, Canada, Argentine, Siberia and the United States of America. Next in importance is margarine, the British production of which does not suffice for the consumption, so that large quantities must be imported from Holland, edible olive oil from Italy, the south of France, Spain and the Mediterranean ports generally. Coco-nut oil and copra, both for edible and technical purposes, are largely shipped to Great Britain from the East Indies and Ceylon, Java and the West Indies. Of lesser importance are greases, which form the by-product of the large slaughter-houses in the United States and Argentina, and American (Canadian) and Japanese fish oils.
On the continent of Europe the largest oil-trading centres are on the Mediterranean (Marseilles and Triest), which are geographically more favourably placed than England for the production of such edible oils (in addition to the home-grown olive oil) as arachis oil, sesame oil and coco-nut oil. Moreover, the native population itself constitutes a large consumer of these oils. In the north of Europe, Hamburg, Rotterdam, Antwerp and Copenhagen are the largest centres of the oil and fat trade. Hamburg and its neighbourhood produces, curiously enough, at present the largest amount of palm-nut oil. The United States takes the foremost place in the world for the production of cottonseed and maize oils, lard, bone fat and fish oils. Canada is likely to outstrip the United States in the trade of fish and blubber oils, and in the near future Japan bids fair to become a very serious competitor in the supply of these oils. Vast stores of hard vegetable fats are still practically wasted in tropical countries, such as India, Indo-China and the Sunda Islands, tropical South America, Africa and China. With the improvement in transport these will no doubt reach European manufacturing centres in larger quantities than has been the case hitherto.
Waxes
The waxes consist chiefly of the fatty acid esters of the higher monohydric alcohols, with which are frequently associated free alcohols as also free fatty acids. In the following two tables the “acids” and “alcohols” hitherto identified in waxes are enumerated in a classified order:—
