BY B. C. GREY. 301 



Data for iodine-absorption : 



No.l. 0-47S4grm. fatty acid absorbed 297 cc. N/10 12—78-85% I^- 

 No. 2. 0-4447 grm. fatty acid absorbed 29-2 cc. N/10 I^— 83-3 % I2. 



Slightly impure oleic acid under same conditions : 



No.l. 0-5 grm. absorbed 36-75 cc. N/10 Iodine— 93-2% Ig, 

 N0.2. 0-5 grm. absorbed 36-20 cc. N/10 Iodine— 91 9% l^. 



Separation of satui-ated atid unsaturated Jatty acids. 



The separation is based on tho solubility of the lead-soaps of 

 the higher unsaturated fatty acids, and the insolubility of these 

 of the saturated fatty acids in ether. The method of Dekonigh 

 and Muter, with the modification of Drechsel, was used. Air 

 was carefully excluded prior to determination of iodine-absorptions, 



TJte unsaturated fatty acids of human brain. 



The mean iodine-absorption of the liquid fatty acids was found 

 to be 110-6 (in twelve hours, Hiild). Since, under exactly 

 similar conditions, that for oleic acid was much less than this, it 

 follows that the liquid fatty acids of the human brain are more 

 unsaturated than oleic acid. 



An approximate calculation of the quantity of linoleic acid 

 which this would represent, shows that the liquid acids contain 



Oleic acid 87-8%. 



(Equivalent of) linoleic acid 22-2 %. 



The saturated fatty acids of human brain. 



The fatty acids which were obtained from the ether insoluble 

 soaps, by decomposition with hot HCl, were washed acid-free 

 with boiling water and dried. The ether-solution was decolour- 

 ised with animal-charcoal, and gave, on evaporation, perfectly 

 white fatty acids which set, on cooling, to an amorphous mass. 

 The fatty acid had a faint odour of beeswax. 



The melting point of the solid fatty acids was 51-4°C. 



The mean molecular weight calculated from analysis of lead- 

 soap was 318-7. This interesting result was immediately checked 



