722 MAN'S PHYSICAL WELFARE Sugars and other carbohydrates are compounds in which some carbon atoms are in the first stage of oxidation, while others are in the second stage of oxidation. Such compounds are therefore more readily assimilated. Sucrose May Soon Be Used as an Industrial Raw Material. Recent research has shown that an excellent synthetic rubber can be prepared from sugar as one of its basic raw materials. Sugar may also be used to prepare adhesives and a very bitter substance (superoctacetate) for use in denaturing alcohol. Organic Acids Are Indirect Products of Photosynthesis. Many fruits and vegetables contain organic acids, which give them An organic acid always contains the carboxyl group, their sour taste. O —C—OH, sometimes written, COOH. organic acids are listed as follows: Name Formic acid Acetic acid Butyric acid Palmitic acid Stearic acid Oxalic acid Lactic acid Malic acid Tartaric acid Citric acid Oleic acid H(COOH) CHaCCOOH) Formula CsHtCCOOH) CuHsiCCOOH) CnHssCCOOH) (COOH)—(COOH) C2H4(OH)—(COOH) (COOH)—CH2—CH(OH)- (CHOH)o(COOH)2 C3H4(OH)(COOH)3 CnH33(COOH) -(COOH) Some of the more important Source Ants or stinging nettle Alcoholic fermentation (the acid of vinegar) Present in rancid butter Vegetable and animal fats Vegetable and animal fats Salts of this acid are found in rhubarb Sour milk Apples, pears, and other fruits Grapes and other fruits Citrus fruits Vegetable and animal oils Lactic acid may be obtained from milk sugar (lactose), which occurs in cow's milk to the extent of 5 per cent. The lactose from skim milk, buttermilk, and whey amounts to a yearly production of 2,700,000,000 pounds. In 1938, 5,000,000 pounds of lactic acid were prepared from lactose in the United States. It is used to acidulate various food products including soft drinks, in dyeing, deliming of hides, vegetable tanning, and to produce acrylic acid for the production of polymethyl acrylate plastics, the so-called organic "glass" discussed in Section 6 of Unit IX. Fats and Oils Are Also Indirect Products of Photosynthesis. Plants are able to combine the soluble sugars with nitrogen-containing substances obtained from the soil to forrti proteins. Proteins furnish
PHOTOSYNTHESIS STORES ENERGY 723 the building materials for animal protoplasm, while carbohydrates and fats furnish animal fuel. Rearrangements of the atoms within carbohydrates produce fats and oils. Fats and oils are mainly storage products that serve as important energy reserves for plants and animals. Vegetable and animal fats and oils are mixtures of glycerol esters of certain acids, such as butyric, palmitic, stearic, and oleic acids. An ester is the product of the action of an organic acid with an alcohol (glycerol, C3H5(OH)3, is a trihydric alcohol), in which water is likewise formed. The various fats and oils, such as butter fat, lard, olive oil, cottonseed oil, linseed oil, peanut oil, soybean oil, sesame seed oil, castor oil, tung oil, etc., differ chiefly in the relative amounts of the above esters which they contain. Vegetable and animal fats and oils are very important not only as foods but also as paint vehicles and the raw materials for soaps. Soaps are soluble metallic salts of the above acids, produced by the saponification of the corresponding fats and oils. The action of alkalies such as sodium hydroxide, NaOH, on a fat or oil to produce a soap and glycerol is called saponification. The unsaturated oleic acid which predominates in oils may be hydrogenated to produce stearic acid, which along with palmitic acid predominates in solid fats. Hydrogenation thus changes such oils as cocoanut oil, fish oils, or cottonseed oil to such solid fats as are found in margarine, "Crisco," and other cooking fats. According to one estimate, the entire world's production of fats and oils is 32,000,000 tons per year, about 83 per cent of which is used for foods for man and other animals, 10 per cent for soap, and the remaining 7 per cent for paint and other uses. The Products of American Farms Are Coining into Use as Industrial Raw Materials. In one year the E. I. du Pont de Nemours Company alone used 23,000,000 pounds of fats and oils, and corn products representing the yield from 1,400,000 acres. The Ford Motor Company has used soybean protein to produce fibers on an experimental basis for the upholstery in Ford cars. It also uses soybean oil (600,000 gallons in 1940) to the extent of 35 per cent in its car finishes and soybean meal (400,000 pounds in 1937) to produce plastic molding compounds, cases for steel molds, and foundry sand cores. The Ford factories are painted with a soybeanoil paint.