OLEIC ACID. 237 



odorless oily liquid which solidifies in crystals at about 4 C., which 

 latter melt at 14 C. Oleic acid is insoluble in water, but dissolves 

 in alcohol, ether, chloroform and petroleum ether. With concentrated 

 sulphuric acid and some cane-sugar it gives a beautiful red or reddish- 

 violet liquid whose color is similar to that produced in PETTENKOFER'S 

 test for bile-acids. If a solution of oleic acid in glacial acetic acid is treated 

 with a little chromic acid (in glacial acetic acid) and then with concen- 

 trated sulphuric acid, the green solution gradually becomes violet or 

 cherry-red, and shows two characteristic absorption bands in the green, 

 one a broad band near the blue and a second but fainter band near the 

 yellow (LIFSCHUTZ) . l The barium salt of oleic acid contains 19.65 per 

 cent barium and the silver salt 27.73 per cent silver. 



If the watery solution of the alkali compounds of oleic acid is pre- 

 cipitated with ^ lead acetate, a white, tough, sticky mass of lead oleate is 

 obtained, which is not soluble in water and only slightly in alcohol, but is 

 soluble in ether. This salt is more easily soluble in benzene than the lead 

 salts of stearic and palmitic acids, and this behavior of the lead salts 

 toward ether and benzene is made use of in separating oleic acid from 

 the other fatty acids. 



An acid related to oleic acid, DOEGLIC ACID, which is solid at 4 C., liquid at 

 16 C., and soluble in alcohol, is found in the blubber of the Balcena rostrata. 

 According to BULL this acid is probably only a mixture of oleic acid and another 

 acid gadoleic acid, C^H^C^, having a melting-point of +24.5 C., and occurring 

 in cod-liver oil, herring oil and in whale blubber. In addition to this acid BULL 

 found in cod-liver oil, besides myristic, palmitic, oleic and erucic acids, another 

 acid, having the formula C 16 H 3 o0 2 . According to ELLMER 2 the most abundant 

 acid (80-90 per cent) in cod-liver oil is therapinic acid, CigHiaC^ which is changed 

 into stearic acid by reduction and jecoleic acid, which seems to be identical with 

 BULL'S gadoleic acid. KURBATOFF has demonstrated the presence of linoleic 

 acid in the fat of the silurus, sturgeon, seal, and certain other animals. Drying 

 fats have also been found by AMTHOR and ZiNK 3 in hares, wild rabbits, wild 

 boar, and mountain-cock. 



To detect the presence of fat in an animal fluid or tissue the fat must 

 first be shaken out or extracted with ether. After the evaporation of 

 the ether the residue is tested for fat and fatty acids. The neutral 

 fats are differentiated from the fatty acids by the acrolein test, and the 

 fatty acids by the fact that their solution in a mixture of alcohol and 

 ether has an acid reaction. In separating the fats from cholesterin 

 and other non-saponifiable substances, as well as for the determination 

 of the kind of the various fatty bodies, they are saponified with caustic 

 alkali, alcoholic potash, or with sodium alcoholate. In regard to these 

 operations, as well as the further investigation and the separation of the 



1 Zeitschr. f. physiol. Chem., 56. 



2 Bull, Ber. d. d. chem., Gesellsch., 39; Ellmer, Bioch. Zeitschr., 9. 



* Kurbatoff, Maly's Jahresb., 22; Amthor and Zink, Zeitschr. f. anal. Chem., 36. 



