246 ANIMAL FATS AND PHOSPHATIDES. 



Various methods have been suggested by STRECKER, HOPPE-SEYLER 

 and DIACONOW, THUDICHUM, GILSON, ZUELZER and BERGELL 1 for the 

 preparation of the lecithins. As none of these yield a positively pure 

 product we will here only mention them. According to ERLANDSEN'S 

 experience all methods which are based upon the precipitation of the 

 lecithin as a metallic compound should be avoided. The best method 

 depends upon the solubility of the lecithin in alcohol and in ether in 

 the cold and its precipitation by acetone (ERLANDSEN, H. E. ROAF and 

 E. EDIE 2 ) . The work of ERLANDSEN is especially referred to in the 

 preparation of lecithins. 



For the present we have no quantitative method for estimating 

 lecithin. The methods used in the past, when the amount of lecithin 

 was calculated from the amount of phosphorus contained in the alcohol- 

 ether extract is useless, as in this case the phosphorous content of all 

 the phosphatides is determined and not alone of the lecithins. Even 

 the detection of choline is not evidence, as this base probably occurs also 

 in other phosphatides. In the detection of choline the double platinum 

 compound is ordinarily prepared, and this can be done as described 

 below. In special determinations of lecithin and cephalin KOCH used 

 to heat with hydroiodic acid, and determined the methyl groups split 

 off below 240 and those at about 300. Instead of this he recommends 

 with WOODS 3 to separate the two by precipitation in alcoholic solution. 

 while boiling, with alcoholic lead acetate solution and a little ammonia, 

 which precipitates only the cephalin. 



Of the cleavage products of the lecithins choline is of especially 

 great interest. 



Choline (trimethyloxyethyl ammonium hydroxide), 



/CH 2 .CH 2 .(OH) 

 C 5 H 15 N0 2 , = HO.N< 



\CH 3 ) 3 , 



stands in close "relation to jthe poisonous base neurine (trimethylvinyl 



/(CHs)s 



ammonium hydroxide), HO.N<T , which according to BRIEGER 



X CH:CH 2 



can be formed from choline by the action of bacteria, and also to mus- 



XCH 3 ) 3 

 carine, HO.N\ , which is the aldehyde of choline and occurs in 



X CH 2 CHO 



/ \ 

 the fly agaric, and also to betaine, trimethyl glycocoll, (CH 3 ) 3 N<( /CO, 



X 



1 Strecker, Annal. d. Chem. u. Pharm., 148; Hoppe-Seyler and Diaconow, 1. c.; 

 Thudichum, 1. c.; Gilson, Zeitschr. f. physiol. Chem., 12; Zuelzer, ibid., 27; Bergell, 

 Ber. d. d. chem. Gesellsch., 33. 



2 Erlandsen. 1. c.; Roaf and Edie, Thompson Yates Laboratory Reports, Vol. 6 

 part I, 1905. 



3 Koch and Woods, Journ. of biol. Chem., 1. 



