100 PALMITIC ACID, ETC. 



13. Palmitic acid, C 16 H 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 acid, C^II^O 2 . On the occurrence and 



E reparation see Palmitic Acid. Crystallizes from alco- 

 ol in laminae; fuses at 69.2, and congeals in crystal- 

 line scales. 



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

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

 ceum. 



17. Benic acid, C 22 H 44 2 . In the oil expressed from 

 the nuts of Moringa nux Behen. 



18. Hydnic acid, C 25 IF0 2 . In the anal glands of 

 Hicena striata. 



