264 PROPERTIES OF NEUTRAL FATS. [BOOK I. 



solution a syrupy liquid glycerin is left. This instructive method 

 of preparing glycerin is not at present employed in the arts, the 

 substance being now obtained by decomposing and distilling the 

 neutral fats by means of superheated steam. 



Properties Glycerin is a colourless, syrupy liquid of intensely 



of Glycerin. sweet taste, having a specific gravity of T27, and 

 soluble, in all proportions, in water. It becomes solid at 40 C. It 

 boils at 280. When heated with the fatty acids it combines with 

 them, forming ethers which are constituted as the fats. Thus 

 by the action of acetic acid on glycerin at 100C. a body termed 

 monacetin is obtained ; by the action of acetic acid at a higher tem- 

 perature diacetin is obtained, and again by reacting further with 

 acetic acid on the latter body, triacetin is formed. The H of the 

 three hydroxyls of glycerin is in this case successively replaced. 



(OH (OH (OH (OCTLO 



C 3 H fi toH C 8 H 6 JOH C 8 H 6 toC 2 H 3 C 3 H 6 -toC 2 H 8 



(OH (OC 2 H 3 (OC 2 H 3 (OC 2 H 3 



Glycerin. Monacetin. Diacetin. Triacetin. 



When glycerin is subjected to the prolonged action of yeast, 



O TT Ol 

 it yields propionic acid 3 jj| 0. 



When distilled with hydriodic acid glycerin yields isopropyl 

 iodide : 



CfLfl, + 5HI = CVHJ + SHp +2 I 2 . 



Glycerin. Hydriodic Isopropyl Water, 

 acid. iodide. 



When heated with phosphorus pentoxide, or acid potassium 

 sulphate, or subjected to destructive distillation, glycerin yields 

 acrolein (C 8 H 4 0), which is the aldehyde of allyl-alcohol (C 3 H 5 OH) ; this 

 substance boils at 52'4. Its vapour possesses an intensely irritating 

 and characteristic odour. 



Fatty matters found in the adipose tissue of certain of the lower animals. 



Spermaceti. In addition to the three neutral fats which have been men- 

 tioned other fats occur in certain members of the animal kingdom. 

 In spermaceti, which is a fatty substance contained in the cranial sinuses of 

 whales, there are no glycerides, but the fats appear to be derivatives of cetyl- 



alcohol l6 jg- 3 4 0, a solid body melting at 50, the chief compound being 



cetyl-palmitate ; when saponified, spermaceti yields, in addition, stearic, 

 myristic and lauric acid. It is worthy of notice that cetyl-alcohol can 

 be artificially oxidized so as to yield palmitic acid. 



Bees' wax In Chinese wax which is produced by the Coccus ceriferus, 



and in bees' wax, the product of the common bee, the portion of 



the substance which is soluble in boiling alcohol contains ceryl-cerotate 



