TISSUES OF THE CONNECTIVE SUBSTANCE. 245 



Palmitin, TRIPALMITIN, 3 H 6 (OH3i0 8 ) 3 . Of the two solid 

 varieties of fats, palmitin is the one which occurs in predominant 

 quantities in human fat (LANGER). Palmitin is present in all 

 animal fats and in several kinds of vegetable fats. A mixture of 

 sterin and palmitin was formerly called MARGARIN.* 



Palmitic acid, C 16 H 38 2 . As to occurrence about the same remarks 

 apply as to stearic acid. The mixture of these two acids has been 

 called margaric acid, and this mixture occurs often as very long, 

 thin, crystalline plates in old pus, in expectorations from gang- 

 rene of the lungs, etc. 



Palmitin crystallizes, on cooling from a warm saturated solution 

 in ether or alcohol, into starry rosettes of fine needles. The mix- 

 ture of palmitin and stearin, called margarin, crystallizes, on cool- 

 ing from a solution, as balls or round masses which consist of short 

 or long, thin plates or needles which often appear like blades of 

 grass. Palmitin, like stearin, has a variable melting and solidify- 

 ing point, depending upon the way it has been previously treated. 

 The melting-point is often given as-f 62 and the solidifying-point 

 as + 45 C. 



Palmitic acid crystallizes from an alcoholic solution in tufts of 

 fine needles. It melts at -f- 62 C.; still the admixture with stearic 

 acid, as HEINTZ has shown, essentially changes the melting and 

 solidifying points according to the relative amounts of the two acids. 

 Palmitic is somewhat more soluble in cold alcoliol than stearic acid ; 

 but they have about the same solubility in boiling alcohol, ether, 

 chloroform, and benzol. 



Olein, TRIOLEIN, CsH^CwHasO.^ , is present in all animal fats 

 and in greater quantities in plant fats. It is a solvent for stearin 

 and palmitin. Oleic acid, ELAIC ACID, C^HaA, occurs probably 

 as soaps in the intestinal canal during digestion and in the chyle. 



Olein is, at ordinary temperatures, a nearly colorless oil of a 

 specific gravity of 0.914, without odor or marked taste. It solidifies 

 in crystalline needles at 5 C. It becomes rancid quickly if 

 exposed to the air. It dissolves with difficulty in cold alcohol, but 

 more easily in warm alcohol or in ether. It is converted into its 

 isomer, ELAIDI^, by nitrous acid. 



i This mixture must not be confounded with the synthetically-prepared 

 neutral fat called trimargarin. 



