Acids of Many Uses From Corn

Most of the commercial sugar acids come from dextrose, the sugar derived from corn. They are cheap and mild and, chemically, maids-of-all-work. Their uses range from the simple process of cleaning milk cans and bottles to the complex production of vitamins. Veterinarians and farmers know best the calcium salt of gluconic acid, which they use for the treatment of milk fever in cows and which doctors sometimes recommend for bee stings. The housewife is most familiar with cream of tartar, an ingredient of the baking powder she uses for her pies and cakes. Citric acid, the acid that gives the tang to citrus fruit?, she also uses for flavoring lemon pies. Its magnesium salt—citrate of magnesia—has often been prescribed as a laxative for her family. No doubt she is also acquainted with ascorbic acid, the sugar acid that is made in chemical factories and is the same as the vitamin C in oranges and lemons. Chemists have known about the sugar acids for a long time, but new uses for them are being discovered constantly. For instance, doctors recently learned that glucuronic acid, first isolated from the body in 1875, may relieve the pains of rheumatism and sciatica. The versatile nature of the sugar acids has aroused increasing interest in them as raw materials for the production of such things as plastics, detergents, and medicines. More attention is being given, consequently, to the development of practical methods for obtaining them from dextrose. Processes for the fermentation of dextrose to citric, gluconic, 2-ketogiuconic, 5-ketogluconic, a-kctoglutaric, and itaconic, and similar acids have been developed in the laboratories of the Department of Agriculture. Some, particularly those for citric and gluconic acids, have achieved commercial importance. The large-scale production of itaconic acid appears promising. Lactic acid, a widely used food acid, is being produced in large volumes by the corn-products industries by fermentation of cornstarch hyclrolyzates. The acids I have mentioned have also been made by nonfermentative methods, but of the purely chemical processes only those for obtaining gluconic and itaconic acids merit consideration from a practical standpoint. Some years ago workers at the National Bureau of Standards devised a procedure for the electrolytic oxidation of corn sugar to gluconic acid. It appears to be competitive with the fermentation method. The electrolysis is carried out between carbon electrodes in the presence of bromides and calcium carbonate buíTer, and the gluconic acid is neutralized as it is formed to give calcium gluconate. Itaconic acid was originally produced in pilot-plant quantities from citric acid. The dehydration of citric acid with mineral acids yields aconitic acid, which is readily decarboxylated to itaconic acid. More recently, however, chemists at the Southern Regional Research Laboratory have demonstrated that the calcium magnesium aconitate present in sugarcane molasses can be recovered in commercial amounts without significantly altering the proc-