38 FATS, ETC. [APP. 



Palmitin (Tri-palmitin). 'JP&L <V 



The following reaction for the formation of this fat is typical for all 

 the others : 



Glycerin. Palmitic acid. Palmitin. 



C * H 4o+3 C ' H "io- H < 

 Hj' + H / -(C 16 H 3 , 



Palmitin is slightly soluble in cold alcohol, readily so in hot alcohol, 

 or in jether; when pure it crystallises in fine needles; if mixed with 

 stearin, it generally forms shapeless lumps, although the mixture may at 

 times assume a crystalline form, and was then regarded as a distinct body, 

 namely margarin. It possesses three different melting points, according 

 to the previous temperatures to which it has been subjected. It solidifies 

 in all cases at 45 C. 



Preparation. From palm oil, by removing the free palmitic acid 

 with alcohol, and crystallising repeatedly from aether. 



Stearin (Tri-steariu). /r , C *?' A O.. 



(Ujgll^Us)! 



This is the hardest and least fusible of the ordinary fats of the 

 body; is also the least soluble, and hence is the first to crystallise out 

 from solutions of the mixed fats. It crystallises usually in square 

 tables. It presents peculiarities in its fusing points similar to those of 

 palm it in. 



Preparation. From mutton suet, its separation from palmitin and 

 olein being effected by repeated crystallisation from aether, stearin being 

 the least soluble. 



Olein (Tri-olein). Q 8 



^3^5 j 



Is obtained with difficulty in the pure state, and is then fluid at 

 ordinary temperatures. It is more soluble than the two preceding ones. 

 It readily undergoes oxidation when exposed to the air, and is converted 

 by mere traces of N0 2 into a solid isomeric fat. Olein yields, on dry 

 distillation, a characteristic acid, the sebacic, and is saponified with much 

 greater difficulty than are palmitin and stearin. 



Preparation. From olive oil, either by cooling to 0. and pressing 

 out the olein that remains fluid ; or by dissolving in alcohol and cooling, 

 when the olein remains in solution while the other fats crystallise out. 



Glycerin C ^F 5 | 0.. 



This principal constituent of the neutral fats may. as above stated, 

 be looked upon as a triatoniic alcohol. 



