COMPARISON OF FATTY ACIDS. 



23 



None of the acids of this series absorb iodine or bromine, as 

 they are saturated compounds, and are not appreciably attacked 

 by strong sulphuric acid or fused alkalies ; the lead, copper, and 

 zinc salts of the lower members of the series (up to lauric) are 

 soluble in ether, but lead, copper, and zinc myristate, palmitate, 

 and stearate are not very soluble in this menstruum. 



Acid of the Series, aH^COOH Oleic Acid, C 17 H 33 .COOH. 

 This acid is probably a constituent of butter ; it is extra- 

 ordinarily difficult to prepare it in the state of purity, as it is 

 altered by exposure to the air, and no well-defined stable com- 

 pound is known. It is extremely doubtful whether it has ever 

 been isolated ; the formula given for the acid is to some extent 

 a matter of conjecture, as there is great probability that the 

 analyses from which it was deduced were made on impure 

 products. For the same reason there is some doubt as to its 

 properties. 



The following properties are assigned to oleic acid : A colour- 

 less liquid free from smell, which moistens the skin, solidifies 

 at 4 C., and melts at 14 C. Specific gravity at 14 C. 0-898, 

 and at 100 C. 0-876. It cannot be distilled under atmospheric 

 pressure, but boils under 100 mm. pressure at 286 C. It can 

 be easily distilled below 270 in a current of superheated 

 steam. 



Oleic acid is insoluble in water, but very soluble in alcohol 

 even if considerably diluted. To a solution of 1 c.c. of oleic acid 

 in 95 per cent, alcohol 2-2 c.c. of a mixture of equal parts of acetic 

 acid and water can be added without causing precipitation ; 

 further quantities, however, throw the oleic acid out of 

 solution. 



On exposure to the air it turns yellowish, and becomes rancid ; 

 it then reddens blue litmus paper, while pure oleic acid is said 

 not to do so. 



By the oxidation of oleic acid dioxystearic acid is formed. 



