100 PALMITIC ACID, ETC. 



13. Palmitic ^ add, C 16 II 32 2 . Palmitic and stearic 

 acids, in the form of glycerin compounds, constitute 

 the principal ingredients of most solid fats. It is present 

 in large quantity, and partially in a free condition, in 

 palm oil.^ In order to prepare it from fats, these are 

 heated with caustic potassa (saponified), the soap (potas 

 sium palmitate and stearate) precipitated from the solu 

 tion and decomposed by hydrochloric acid. The acids 

 are now dissolved in alcohol, and separated from each 

 other by means of partial precipitation with magnesium 

 acetate. If only 4 of the amount of the magnesium salt 

 necessary for complete precipitation is added, magne 

 sium stearate falls down almost free of the palmitate ; 

 the succeeding precipitations contain the stearate mixed 

 with palmitate ; the last precipitations are almost pure 

 magnesium palmitate. The precipitates are now de 

 composed separately by hydrochloric acid, and the free 

 acids treated a few times more in the same manner. 



Fine white needles, which congeal after fusion in the 

 form of a scaly, crystalline mass. Fusing point, 62. 



14. Margaric acid, C 17 H 34 2 . Probably does not occur 

 in nature. That which was formerly designated as 

 such has proven to be a mixture of palmitic and stearic 

 acids. ^ It is prepared artificially by boiling cetyl cya 

 nide with caustic potassa. It resembles palmitic acid. 



15. Stearic add, C 18 II 36 2 . On the occurrence and 

 preparation see Palmitic Acid. Crystallizes from alco 

 hol in laminae; fuses at 69.2, and congeals in crystal 

 line scales. 



16. Arachidic add, C 20 H 40 2 , is contained in oil of 

 earth-nut and in the fruit kernels of Nephelium lappa- 

 ceum. 



17. Bertie acid, C 22 I1 44 2 . In the oil expressed from 

 the nuts of Moringa mix Behen. 



18. Hydnic add, C 25 IP0 2 . In the anal glands of 

 Micena striata. 



