Dr. Playfair on Palmic Acid. 475 



LXVII. On Palmic Acid, a Fat Acid related to the Margaryle 

 Series. By Lyon Playfair, Esq., Ph.D.* 



"DOUDETf has shown that castor oil is solidified by nitric 

 *-* acid containing peroxide of nitrogen (N0 4 ), and that the 

 latter is itself sufficient for this purpose. He described the 

 solid fat thus procured under the name of palmine, and the fat 

 acid obtained by the decomposition of its soap as palmic acid. 



Palmic acid is stated to have a fusing-point of 50° C, al- 

 though described as usually having it a few degrees lower ; 

 but I have never succeeded in procuring it of a higher melt- 

 ing-point than 45° to 46° C. (113° to 114° F.). Boudet did 

 not analyse this acid, nor has it, as far as I am aware, engaged 

 the attention of any other chemist. The singular nature of 

 the compound formed merits a careful examination; so with- 

 out assigning to myself the task of determining at present the 

 reason of the transformation, I propose to examine the com- 

 position of palmine and palmic acid. 



Palmine, as well as castor oil, contains glyceryle, as has pre- 

 viously been asserted by Bussy, Lecanu and Boudet, but the 

 solidification of the oil is not due to the presence of this com- 

 pound. In order therefore to be more assured of the purity 

 of the acid formed, I operated principally upon the acids of 

 castor oil. For this purpose, castor oil is saponified by caustic 

 soda and the soap separated by common salt. The soap re- 

 moved from the liquor is redissolved in pure water and again 

 separated by salt; and this operation is repeated until the 

 excess of caustic soda is removed. The soap is now quite 

 Avhite and readily soluble in hot water, from which solution 

 the fatty acids are separated by the addition of muriatic acid. 

 They are of a pale-olive colour, and are purified from adhering 

 muriatic acid by repeated washings with water. 



The acids thus procured are mixed with diluted nitric acid, 

 through which is passed a stream of peroxide of nitrogen, made 

 by the action of nitric acid on starch. The acids, which are 

 previously fluid, soon become solid, and finally acquire the 

 colour and consistence of pale yellow bees'-wax. This solid 

 substance is washed with hot water till all the nitric acid is 

 removed, the washing being performed by melting it in hot 

 water, and drawing off the latter by ft siphon. This fat is not 

 palmine, but the acid contained in that substance ; it differs 

 from palmine by not containing glycerine. Thus prepared, it is 



* Communicated by the Chemical Society; having been read May 18, 

 1846. 



f Annates de Chimie et de Physique, 1. 1. p. 411. 



2 K 2 



