In the manufacture of foods, drugs, and cosmetics, oil cannot be employed as a lubricant because it might come in contact with the products and contaminate them. Therefore, the nontoxic glycerol is used to reduce friction in pumps and bearings. Gasoline and other hydrocarbon chemicals dissolve oil-based greases, so glycerin is used in pumps for transferring these fluids. Glycerol is also applied to cork gaskets to keep them flexible and tough when exposed to oils and greases as in automobile engines. Glycerin is used as a lubricant in various operations in the textile industry, and can be mixed with sugar to make a nondrying oil. Glycerol does not turn into a solid until it is cooled to very cold temperature. This property is utilized to increase the storage life of blood. When small amounts of glycerin are added to red blood cells, they can be frozen and maintained for up to three years.
Chemical derivatives of glycerol or propane- 1,2,3-triol are important in a wide range of applications.Nitroglycerin is the trinitrate derivative of glycerol. One application of this chemical is as the key ingredient in the manufacture of dynamite explosives. Nitroglycerin can also be used in conjunction with gun cotton or nitrocellulose as a propellant in military applications. In the pharmaceutical industry, nitroglycerin is considered a drug to relieve chest pains and in the treatment of various heart ailments. Another derivative, guaiacol glyceryl ether, is an ingredient in cough medicines, and glycerol methacrylate is used in the manufacture of soft contact lenses to make them permeable to air. Glycerol esters are utilized in cakes, breads and other bakery products as lubricants and softening agents. They also have similar applications in the making of candies, butter and whipped toppings. A specially designed glycerol ester called caprenin can be used as a low calorie replacement for cocoa butter.
Glycerol is added during the manufacture of soaps in order to prepare shiny transparent bars. The trihydric alcohol structure of glycerin makes it a useful chemical in the manufacture of various hard foams, like those that are placed under siding in buildings and around dish washers and refrigerators for insulation and sound proofing. Analogously, the chemical structure of glycerol makes it an excellent catalyst in the microbiological production of vinegar from alcohol.
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