=278. Composition.=—Fats and oils are composed chiefly of salts produced by the combination of the complex base glycerol with the fat acids. Certain glycerids, as the lecithins, contain also phosphorus in organic combinations, nitrogen, and possibly other inorganic constituents in organic forms. By the action of alkalies the glycerids are easily decomposed, the acid combining with the inorganic base and the glycerol becoming free. The salts thus produced form the soaps of commerce and the freed base, when collected and purified, is the glycerol of the trade. When waxes are decomposed by alkalies, fatty acids and alcohols of the ethane series are produced. The natural glycerids formed from glycerol, which is a trihydric (triatomic) alcohol, are found in the neutral state composed of three molecules of the acid, united with one of the base. If R represent the radicle of the fat acid the general formula for the chemical process by which the salt is produced is: Glycerol. Acid. Salt. Water. O.H O.R C₃H₅O.H + 3R.OH = C₃H₅O.R + 3H₂O. O.H O.R The resulting salts are called triglycerids or neutral glycyl ethers.[230] In natural animal and vegetable products, only the neutral salts are found, the mono- and diglycerids resulting from artificial synthesis. For this reason the prefix tri is not necessarily used in designating the natural glycerids, stearin, for instance, meaning the same as tristearin. =279. Principal Glycerids.=—The most important glycerids which the analyst will find are the following: Olein, C₃H₅O(O.C₁₈H₃₃O)₃. Stearin, C₃H₅O(O.C₁₈H₃₅)₃. Palmitin, C₃H₅O(O.C₁₆H₃₁O)₃. Linolein, C₃H₅O(O.C₁₈H₃₁O)₃. Butyrin, C₃H₅O(O.C₄H₇O)₃. Olein is the chief constituent of most oils; palmitin is found in palm oil and many other natural glycerids; stearin is a leading constituent of the fats of beeves and sheep, and butyrin is a characteristic constituent of butter, which owes its flavor largely to this glycerid and its nearly related concomitants.