134 FATTY SUBSTANCES. 



The discovery of the vegetable bases is due to Sertuerner, wh(.», 

 in 1804, indicated the existence of morphine in opium. The ma- 

 jority of the vegetable alkalies are insoluble, or little soluble in 

 water ; all are soluble in alcohol ; some of them are sutRciently 

 volatile to be susceptible of distillation. 



In elementary composition they are all very much alike, consist- 

 ing of various, but, in each instance, definite proportions of carbon, 

 hydrogen, oxygen, and azote, the carbon varying from about 50 to 

 75, the hydrogen from 6 to 12, the oxygen from 8 or 9 to 27 and 

 even 37, and the azote from 1.6 to 12, 28, and even 35 per cent. 



OF FATTY SUBSTANCES. 



Under this title I comprise all the oily substances, liquid or solid, 

 and those that are analogous to wax, which are found disseminated 

 in different organs of plants. A character common to almost all 

 fatty substances, is insolubility in water. They dissolve in sensible 

 quantity in alcohol, and especially in ether. Fatty substances may 

 be divided into two classes : one including those which are easily 

 modified by the action of alkalies, and which form soaps ; the other 

 not susceptible of this action, not susceptible of saponification, or, at 

 all events, that are only attacked by alkalies in very particular cir- 

 cumstances. 



When a mixture of fat oil and a solution of caustic alkali are 

 heated, the oil is soon observed to incorporate with the alkaline 

 liquid. After boiling for some time, if the alkali is in excess, clots 

 or flocks appear, and in removing the excess of liquid a white mass 

 is obtained which is soluble in water — the oil is saponified ; and the 

 product of the saponification is combined with a portion of the alkali 

 which has been employed. If into a hot solution of this soap a 

 quantity of hydrochloric acid be poured, the acid seizes upon the pot- 

 ash or the soda, setting at liberty the fatty body which had been 

 combined with the alkali, and which collects on the liquid. It is 

 easy to discover that the fatty matter thus collected is no longer the 

 same as that which had been originally employed ; for example, it is 

 completely soluble in boiling alcohol, which, on cooling, deposites 

 brilliant pearly crystals of a fatty substance possessing acid proper- 

 ties. By evaporating the alcohol from which these crystals are 

 formed, an additiona quantity is obtained, and, when the alcohol is 

 entirely dissipated, another unctuous body is obtained, having also 

 acid properties. Three acids having distinguishing characters are, 

 in fact, obtained by the action of alkalies upon fatty substances : the 

 stearic, margaric, and oleic acids. The alkalies consequently trans- 

 form neutral oily bodies into acid substances, as first shown by the 

 admirable researches of M. Chevreul, before whose time it was al- 

 ways assumed that soap was the result f f a direct union of fatty 

 matters with alkalies. The fatty acids arc not the only products of 

 saponification, there are several others, particularly glycerine, which, 

 however, need not occupy us particularly here. 



The experiments of M. Chevreul would lead us to view all fatty 



