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WHAT IS GLYCERIN?
Glycerin, sometimes spelled glycerine, is a commercial product whose principal component is glycerol. The terms glycerin, glycerine, and glycerol are often used interchangeably in the literature.
Glycerin is one of the most versatile and valuable chemical substances known to man. It possesses a unique combination of physical and chemical properties that are utilized in myriad products. Glycerin has over 1,500 known end uses, including many applications as an ingredient or processing aid in cosmetics, toiletries, personal care, drugs, and food products. In addition, glycerin is highly stable under typical storage conditions, compatible with many other chemical materials, virtually non-toxic and non-irritating in its varied uses, and has no known negative environmental effects. A water clear, odorless, viscous liquid with a sweet taste, glycerin is derived from both natural and petrochemical feedstocks. It occurs in combined form (triglycerides) in all animal fats and vegetable oils and constitutes, on average, about 10 percent of these materials. Glycerin is obtained from fats and oils during soap and fatty acid production and by transesterification (an interchange of fatty acid groups with another alcohol). It is subsequently concentrated and purified prior to commercial sale. Synthetic glycerin is produced from petrochemical building blocks via several processing steps designed to achieve the desired concentration and high product quality. Glycerin, whether recovered from triglycerides or synthesized, is principally used as a highly refined and purified product, with a very high concentration of glycerol.

Glycerol, the main component of glycerin, has the chemical formula C 3 H 5 (OH)3 . It is a trihydric alcohol, possessing two primary and one secondary hydroxyl groups, which are its potential reaction sites and the basis for glycerin’s versatility as a chemical raw material. For example, glycerol esters, the reaction products of glycerin with various fatty acids form an important class of derivatives that are extensively used in the food industry. The physical properties and characteristics of glycerin are as significant as its chemical properties for many applications. These qualities enable glycerin to be used as a humectant, plasticizer, emollient, thickener, solvent, dispersing medium, lubricant, sweetener, bodying agent, antifreeze and processing aid. It is not unusual for glycerin to contribute two or more features or attributes to a product or application. In all applications, whether as a reactant or as an additive, the virtual non-toxicity and overall safety of glycerin is always of significant benefit. Glycerin applications appear to be limited only by the imagination and creativity of the scientific and technical communities.

Most of the glycerin marketed today is manufactured to meet the stringent requirements of the United States Pharmacopeia (USP) and the Food Chemicals Codex (FCC). However, technical grades of glycerin that are not certified as USP or FCC are available. Glycerin is used in many consumer products such as personal care preparations, cosmetics, pharmaceuticals and foods because of its contribution to product properties, stability and compatibility with a wide variety of chemicals, and relative non-toxicity. For these consumer-oriented applications, the quality and purity of the ingredients is crucially important. The use of USP and FCC- certified glycerin, versus technical grade glycerin, in consumer product applications ensures that the manufacturer has specified the glycerin quality and consistency required for these products.

WHAT DOES USP MEAN?
The abbreviation USP stands for United States Pharmacopeia, a document first published in 1820 by the Medical Society of New York State. Recognized as official by Congress in 1848, this document was used as a standard reference by physicians for prescribing medicines. Today, the USP includes chemical descriptions, identifying tests, and purity tests, primarily for active ingredients. All materials listed in the USP are considered drugs by law and subject to all the U.S. Food & Drug Administration requirements pertaining to drugs. Labeling a product or a substance as USP implies that it conforms to all the legal requirements of the FDA and that it was produced in accordance with the principles outlined in FDA’s Good Manufacturing Practices (GMP). A new edition of the USP is published every five years in the years ending in "0" and "5," with ongoing revisions and additions issued during the interim years.
Many other nations also have compiled an official national pharmacopeia, similar in scope and content to the USP. Currently, there is a collaborative international program to harmonize the glycerin monographs in the USP and in the European Pharmacopeia, which may later be expanded to include other nations.