STEARIC ACID This body is the most abundant onstituent in all solid fatty substances. It exists in them in the state f stearin, a combination of stearic acid with the basis of GLYCERIN. 'he relation which stearic acid bears to other acids, that occur in fats nd oils, will be readily seen on perusing the article on FATTY ACIDS. Itearic acid is sometimes met with under the name of bassic acid and tearophanic add, and under the name of anamirtic acid occurs in the eeds of the anamirta cocculus.
Stearin is, for experimental purposes, generally prepared from autton suet, from a solution of which in hot ether it crystallises out ,n cooling. By one or two recrystallisations it is perfectly purified. Ins prepared stearin forms white, pearly, lamellar crystals. When mite dry it is not greasy to the touch, and is easily pulverised. It oelts when heated to about 144° Fahr., but by repeated fusions )ecomes more and more dense, and requires an increased temperature or its liquefaction. It is almost insoluble in water and only slightly oluble in cold alcohol or ether. Seven times its weight of boiling leohol dissolves it, and less than that proportion of hot ether. By lestructive distillation it yields oily and fatty hydrocarbons, acetic cid, acrolein, margaric acid, &e. By heating stearic acid with glycerin n closed vessels Berthelot succeeded in obtaining artificial stearins, containing one, two, or three equivalents of stearic acid united with ;1yeerin. [CiLvemmr, Monostearin, Distearin, Tristearin.] Stearic add. Obtained by saponifying stearin with caustic potash Lnd then precipitating the stearic acid by the addition of hydrochloric Ir tartaric acid to the hot solution of the resulting soap. It may be mrified by washing with cold alcohol and recrystallising from hot dcohol. It may also be prepared directly from mutton suet by saponi !ying and decomposing, as above described, and then submitting the woduct to strong pressure ; the greater part of the oleic acid is in this say removed and the remaining stearic acid obtained pure after one or ;wo crystallizations.
Stearic acid crystallises from hot ether in transparent, colourless, a rhombic outline. Its fusing point is about 167° Fahr.; but it having not resolidify until the temperature falls to about 158° Fahr. At higher temperatures it volatilises and is partially lecomposed. It is insoluble in water ; its alcoholic solution reddens
litmus paper ; it slightly decomposes carbonates in the cold, but com pletely on being boiled with them. A mixture of stearic and palmitic acids melts at a lower temperature than either acid does alone ; thirty parts of the former and seventy of the latter fuse nearly 20 degrees lower than the mean melting point of the two. Chlorine and bromine act upon stearic acid, especially when they are heated together, giving rise to chlor- and brow- derivatives. Such a body is chlorostearic acid, containing Nitric acid oxidises it to suberie, pimelic, adipic, succinic, capnc, cenanthylic, caproic, and other acids. Anhydrous phosphoric acid removes from stearic acid the elements of two equivalents of water, and leaves a brittle, obscurely-crystalline mass, having the' composition Perchloride of phosphorus also acts ;energetically upon stearic acid. A mixture of stearic acid and glycerin maintained at 212° Fahr., and saturated with hydrochloric acid gives rise to stearoeldorhydrin, a crystalline body containing stearenc or margarone, is a colourless crystalline body produced on stearic acid with one fourth its weight of quick lime. It fuses at 171° Fahr. and resolidifies at 162° Fehr. Its com position has not been satisfactorily determined.
Stcaratcs are combinations of stearic acid with bases, and the com pounds, like those of the other FATTY ACIDS, are termed soaps. titearates are mostly- fusible and decompose when strongly heated. Those of the alkalies are readily formed on heating stearin with the alkali, as in the ordinary method of making soap. From the alkaline stearates other stearates may be formed by precipitation with a soluble salt of the metal whose stearate is required ; the alkaline stearates being soluble in the stearates of other metallic oxides being insoluble. The neutral stearate of potash contains the add stearate (K0,110,2C,„IL,00. Stcarate of lime Stcarate of surer (AgO, Stcarate of ethyl (steam ether) Stearanilide or phenyl-stearamide is obtained on. distilling stearic acid with excess of aniline. It crystallises in needles and contains (N, 1I / For the economical applications of stearlc acid, see CANDLE MANU FACTURE; SOAP.