To understand this interesting reaction which is profoundly affecting international relations it will be necessary to dip into the chemistry of the subject. Here are the symbols of the chief ingredients of the fats and oils. Please look at them.
| Linoleic acid | C18H32O2 |
| Oleic acid | C18H34O2 |
| Stearic acid | C18H36O2 |
Don't skip these because you have not studied chemistry. That's why I am giving them to you. If you had studied chemistry you would know them without my telling. Just examine them and you will discover the secret. You will see that all three are composed of the same elements, carbon, hydrogen, and oxygen. Notice next the number of atoms in each element as indicated by the little low figures on the right of each letter. You observe that all three contain the same number of atoms of carbon and oxygen but differ in the amount of hydrogen. This trifling difference in composition makes a great difference in behavior. The less the hydrogen the lower the melting point. Or to say the same thing in other words, fatty substances low in hydrogen are apt to be liquids and those with a full complement of hydrogen atoms are apt to be solids at the ordinary temperature of the air. It is common to call the former "oils" and the latter "fats," but that implies too great a dissimilarity, for the distinction depends on whether we are living in the tropics or the arctic. It is better, therefore, to lump them all together and call them "soft fats" and "hard fats," respectively.
Fats of the third order, the stearic group, are called "saturated" because they have taken up all the hydrogen they can hold. Fats of the other two groups are called "unsaturated." The first, which have the least hydrogen, are the most eager for more. If hydrogen is not handy they will take up other things, for instance oxygen. Linseed oil, which consists largely, as the name implies, of linoleic acid, will absorb oxygen on exposure to the air and become hard. That is why it is used in painting. Such oils are called "drying" oils, although the hardening process is not really drying, since they contain no water, but is oxidation. The "semi-drying oils," those that will harden somewhat on exposure to the air, include the oils of cottonseed, corn, sesame, soy bean and castor bean. Olive oil and peanut oil are "non-drying" and contain oleic compounds (olein). The hard fats, such as stearin, palmitin and margarin, are mostly of animal origin, tallow and lard, though coconut and palm oil contain a large proportion of such saturated compounds.
Though the chemist talks of the fatty "acids," nobody else would call them so because they are not sour. But they do behave like the acids in forming salts with bases. The alkali salts of the fatty acids are known to us as soaps. In the natural fats they exist not as free acids but as salts of an organic base, glycerin, as I explained in a previous chapter. The natural fats and oils consist of complex mixtures of the glycerin compounds of these acids (known as olein, stearin, etc.), as well as various others of a similar sort. If you will set a bottle of salad oil in the ice-box you will see it separate into two parts. The white, crystalline solid that separates out is largely stearin. The part that remains liquid is largely olein. You might separate them by filtering it cold and if then you tried to sell the two products you would find that the hard fat would bring a higher price than the oil, either for food or soap. If you tried to keep them you would find that the hard fat kept neutral and "sweet" longer than the other. You may remember that the perfumes (as well as their odorous opposites) were mostly unsaturated compounds. So we find that it is the free and unsaturated fatty acids that cause butter and oil to become rank and rancid.
Obviously, then, we could make money if we could turn soft, unsaturated fats like olein into hard, saturated fats like stearin. Referring to the symbols we see that all that is needed to effect the change is to get the former to unite with hydrogen. This requires a little coaxing. The coaxer is called a catalyst. A catalyst, as I have previously explained, is a substance that by its mere presence causes the union of two other substances that might otherwise remain separate. For that reason the catalyst is referred to as "a chemical parson." Finely divided metals have a strong catalytic action. Platinum sponge is excellent but too expensive. So in this case nickel is used. A nickel salt mixed with charcoal or pumice is reduced to the metallic state by heating in a current of hydrogen. Then it is dropped into the tank of oil and hydrogen gas is blown through. The hydrogen may be obtained by splitting water into its two components, hydrogen and oxygen, by means of the electrical current, or by passing steam over spongy iron which takes out the oxygen. The stream of hydrogen blown through the hot oil converts the linoleic acid to oleic and then the oleic into stearic. If you figured up the weights from the symbols given above you would find that it takes about one pound of hydrogen to convert a hundred pounds of olein to stearin and the cost is only about one cent a pound. The nickel is unchanged and is easily separated. A trace of nickel may remain in the product, but as it is very much less than the amount dissolved when food is cooked in nickel-plated vessels it cannot be regarded as harmful.
Even more unsaturated fats may be hydrogenated. Fish oil has hitherto been almost unusable because of its powerful and persistent odor. This is chiefly due to a fatty acid which properly bears the uneuphonious name of clupanodonic acid and has the composition of C18H28O2. By comparing this with the symbol of the odorless stearic acid, C18H36O2, you will see that all the rank fish oil lacks to make it respectable is eight hydrogen atoms. A Japanese chemist, Tsujimoto, has discovered how to add them and now the reformed fish oil under the names of "talgol" and "candelite" serves for lubricant and even enters higher circles as a soap or food.
This process of hardening fats by hydrogenation resulted from the experiments of a French chemist, Professor Sabatier of Toulouse, in the last years of the last century, but, as in many other cases, the Germans were the first to take it up and profit by it. Before the war the copra or coconut oil from the British Asiatic colonies of India, Ceylon and Malaya went to Germany at the rate of $15,000,000 a year. The palm kernels grown in British West Africa were shipped, not to Liverpool, but to Hamburg, $19,000,000 worth annually. Here the oil was pressed out and used for margarin and the residual cake used for feeding cows produced butter or for feeding hogs produced lard. Half of the copra raised in the British possessions was sent to Germany and half of the oil from it was resold to the British margarin candle and soap makers at a handsome profit. The British chemists were not blind to this, but they could do nothing, first because the English politician was wedded to free trade, second, because the English farmer would not use oil cake for his stock. France was in a similar situation. Marseilles produced 15,500,000 gallons of oil from peanuts grown largely in the French African colonies—but shipped the oil-cake on to Hamburg. Meanwhile the Germans, in pursuit of their policy of attaining economic independence, were striving to develop their own tropical territory. The subjects of King George who because they had the misfortune to live in India were excluded from the British South African dominions or mistreated when they did come, were invited to come to German East Africa and set to raising peanuts in rivalry to French Senegal and British Coromandel. Before the war Germany got half of the Egyptian cottonseed and half of the Philippine copra. That is one of the reasons why German warships tried to check Dewey at Manila in 1898 and German troops tried to conquer Egypt in 1915.
But the tide of war set the other way and the German plantations of palmnuts and peanuts in Africa have come into British possession and now the British Government is starting an educational campaign to teach their farmers to feed oil cake like the Germans and their people to eat peanuts like the Americans.
The Germans shut off from the tropical fats supply were hard up for food and for soap, for lubricants and for munitions. Every person was given a fat card that reduced his weekly allowance to the minimum. Millers were required to remove the germs from their cereals and deliver them to the war department. Children were set to gathering horse-chestnuts, elderberries, linden-balls, grape seeds, cherry stones and sunflower heads, for these contain from six to twenty per cent. of oil. Even the blue-bottle fly—hitherto an idle creature for whom Beelzebub found mischief—was conscripted into the national service and set to laying eggs by the billion on fish refuse. Within a few days there is a crop of larvae which, to quote the "Chemische Zentralblatt," yields forty-five grams per kilogram of a yellow oil. This product, we should hope, is used for axle-grease and nitroglycerin, although properly purified it would be as nutritious as any other—to one who has no imagination. Driven to such straits Germany would have given a good deal for one of those tropical islands that we are so careless about.