FAT OF COCHINEAL INSECT. 145 



M. Bromeis found that when nitric acid is digested on stearic 

 acid, a violent action takes place, which becomes gradually more 

 moderate, and at last nearly ceases. The stearic acid after this 

 action becomes clear and liquid, and forms a tallowy, solid mat- 

 ter, which melts at 95 or 113, according to the duration of the 

 process. This tallowy matter is margaric acid, mixed with a 

 product proceeding from the oleic acid present, which is easily 

 saponified by potash. It then assumes a blood-red colour, and 

 retains that colour after separation by an acid. The tallowy 

 mass separated from this body was freed from nitric acid by boil- 

 ing it in water. It was then dissolved in hot alcohol, and allowed 

 to cool. The margaric acid was deposited in crystals. It was 

 purified by repeated solutions in alcohol, by saponification and 

 precipitation by an acid. 



Margaric acid resembles stearic acid very closely ; but it 

 melts at 140, according to Chevreul, or 141, according to 

 Bromeis ; while stearic acid requires for fusion the temperature 

 of 158 or 160. 



The constitution of this acid, and its analogy to stearic acid, 

 have been already pointed out. The common base is C 34 H 33 . 

 Margaric acid is C 34 H 33 4. O 3 = 32-625 

 Stearic acid, . 2 (C 34 H 33 ) + O 5 = 64-25 

 Margaric acid, in its hydrous state, contains only 1 atom 

 water, while stearic contains 2. Hence the former combines 

 with only 1 atom of base, while the latter combines with 2. We 

 might also represent the constitution of these acids thus : 

 Margaric acid, C 34 H 33 + O 3 = 32-625 

 Stearic acid, C 34 H 33 4. O 2 4 = 32-125 

 According to that view of their constitution, both, in the hy- 

 drous state would contain 1 atom of water, and both would 

 combine with 1 atom of base. 



CHAPTER IV. 



-OF OILY OXIDES NOT SAPONIFIABLE. 



THE oily bodies from the animal kingdom not capable of 

 being converted into soap are not numerous, and have been but 



K 



