258 M. Chevreul on Fatty Bodies, and [Oct. 



the author takes a review of what he has done in the five preced- 

 ing papers. He observes that in the first he described a body, 

 which unites the characteristic properties of acids to all the 

 generic properties of the fats and oils. This body, which he has 

 named margarine, has served as the type of a new kind of 

 ternary acid, and bears the same relation to the oxygenated 

 vegetable acids as the hydrogenated do to the oxygenated acids 

 in the inorganic kingdom. 



The object of the second memoir was to analyze the products 

 of the saponification of hog's-lard as effected by potash. After 

 having deprived the soap of its margarine, a fatty body was 

 obtained from it which was denominated Jluid fat. This body, 

 like margarine, unites to potash in two proportions, but it differs 

 from it in fluidity, and in the solubility in cold water of its 

 saturated combination with alkali. The examination of the fluid 

 from which the soap is separated has shown that in saponifica- 

 tion a sweet principle is produced, similar to that which Scheele 

 observed in water, in which olive oil has been treated with prot- 

 oxide of lead. These researches then have established that 

 soap, which had been regarded as a compound of a fatty matter 

 and an alkali, is really a double compound of alkali and of two 

 fatty acid bodies. 



The composition of soap being thus determined, in the third 

 memoir the following facts were established : 1 . That the essen- 

 tial products of saponification are margarine, the fluid fat, and 

 the sweet principle ; but that the odorous and colouring prin- 

 ciples found in many soaps appear to be accidental : 2. That 

 oxygen gas is not necessaiy for saponification : 3. That saponi- 

 fied fat is formed of margarine and of the fluid fat, and conse- 

 quently possesses acidity : natural fat is formed of two new 

 proximate principles, one of which is analogous to tallow, and 

 the other to the liquid oil of vegetables ; but both of these 

 principles differ from those of saponified fat; for instead of 

 being acid, they rather appear to possess an alkaline nature : 

 4. The experiments have also shown that the saponification of 

 hog's-lard depends upon two causes that are inseparable ; first, 

 upon the elementary composition of this fat, which is such, that 

 it may be represented either by the two immediate principles 

 which constitute it, or by the sweet principle, margarine, and 

 the fluid fat ; secondly, upon the sweet principle, and still more 

 the margarine and the fluid fat, having an affinity for potash much 

 superior to the immediate principles of fat for the same base, 

 from which it results, that in saponification the potash deter- 

 mines the fat to be converted into the sweet principle and the 

 two acid substances. This total conversion of an organic matter 

 into many substances, which are themselves compounds, and 

 very different from the matter itself, may explain many pheno- 

 mena in physiology, where bodies assume forms totally different 

 from those which they previously possessed. 



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