368 CHEMISTEY. 



seeds, walnuts, sunflower-seeds, hazel-nuts, even apple-seeds, 

 plum and cherry stones, etc. 



514. Composition. The oils and fats are composed most- 

 ly of three ingredients, called stearin, palmitin, and olein. 

 The stearin, when separated from the others, is a solid at 

 all ordinary temperatures, while the olein is a liquid ; the 

 palmitin is midway between the other two. In very cold 

 weather, when a portion of lamp-oil becomes solidified, we 

 have a partial separation between the stearin and the 

 olein. The consistency of fatty substances depends upon 

 the proportions of olein and stearin in them, the former 

 predominating in the liquid, and the latter in the more 

 solid bodies. But these constituents of fats are far from 

 being simple substances. They are compounds formed by 

 the union of acids with a certain b.ase or radical called 

 glyceryl. Thus stearin is a combination of stearic acid 

 with this base, a glyceryl stearate, just as pearlash is 

 potassium carbonate. Likewise olein is glyceryl oleate. 

 Bodies formed after this pattern are called salts in organic 

 chemistry just as in mineral chemistry, the only real differ- 

 ence being that the radicals and the acids in one instance 

 are far more complex than in the other. This the formula) 

 for stearin, palmitin, and olein show : 



Glyceryl, a hydrocarbon radical, (C 3 H 5 )'" 



Stearin, or glyceryl stearate, (C 3 H 5 )"'(C 18 H 35 2 )3 



Palmitin, or glyceryl palmitate, (C 3 H 5 )"'(C 16 H 31 O 2 ) 3 



Olein, or glyceryl oleate, (C 3 H 6 )'"(C 18 H 33 O 2 ) 3 



515. Glycerin. This is a colorless, sirupy liquid, of a 

 sweet taste ; this latter quality gives it its name, which is de- 

 rived from a Greek word glukus^ sweet. It belongs to the 

 class of bodies called alcohols, but is described in this con- 

 nection because it is a product of the decomposition of oils 

 and fats. It is a hydrate of glyceryl, and has the formula 

 C 3 H 5 (IIO) 3 . 



