302 THE PATTY ACIPS OF BRAIN LIPOIDS, I., 



by determination of the saponifying equivalent with KOH. The 

 figures, though low compared with lead-estimation, are con 

 sistently high, and give a mean molecular weight of 308'3. It 

 is probably difficult to obtain the lead-soap pure. 



From these results there can be no doubt that the solid moiety 

 contains fatty acids of molecular weight much higher than those 

 of previously mentioned fatty acids. (The molecular weight of 

 stearic acid is 284). The low melting point of the mixture is 

 also significant, and does not correspond to any simple mixture 

 of palmitic and stearic acids. 



Data for mean molecular tveight. 



02872grm. lead-soap gave 0-10.S3grm. PbSO^ : mean mol. wt. =3187. 

 Saponification with alcoholic KOH 



(1) 3-9812 grm. neutralised 26-0 cc. N/2 KOH, mean mol. wt. =306-8. 

 (2)0-9850 „ „ 31 -See. N/10 KOH ,, „ ,, 309-7. 



(3)1-4786 ,, „ 48-3 cc. N/ 10 KOH „ „ „ 3041. 



(4)1-4786 ,, „ 48-6 cc. N/IO KOH „ „ „ 306-4. 



Separation of the saturated fatty acids. 



This is based on fractional precipitation with magnesium- 

 acetate. 



The separation was carried out with 4-5 grams fatty acid, but 

 the results prove definitely the existence of a fatty acid of high 

 molecular weight in the brain as already mentioned. 



Four small fractions were separated with the following results: 



No.4 was obtained by making filtrate from No.3 strongly 

 ammoniacal, and is probably the same as No.l. 



Fractions 2 and 3 had many characteristics of a mixture of 

 palmitic and stearic acids, but the colour and low melting point 

 _prove them to be more complex. 



