202 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
dissolved in petroleum ether, shaken up in a separating funnel with seventy-five per cent, 
alcohol twice, after which the alcoholic extracts were united, separated from petroleum 
ether by distillation of the latter, and allowed to stand in the cold when cholestearin 
separated out. The alcoholic solution containing the lecithin was separated from the 
precipitated cholestearin and brought down to a syrup at a temperature of 50-60 0 C. 
This syrup was taken up with ether, decanted, filtered, and the ether evaporated off, 
leaving behind almost pure lecithin. A great advance was made in the methods of 
separation of lecithin by Zuelzkr,' who introduced precipitation by acetone in ethereal 
solution as a means of separation. The acetone precipitates the lecithin but leaves 
the fats and cholestearin in solution. Zuelzer, however, still retained the practice 
of repeated extraction of the fresh material with ether, and precipitated the lecithin 
from the united ethereal extracts. It is obvious from the original method of obtaining 
lecithin, in which these ethereal extracts were neglected, and still a yield of lecithin 
obtained from the residue on subsequent treatment with alcohol, that the initial 
extraction of the fresh tissue with repeated quantities of fresh ether is a slow, 
laborious, and incomplete process 2 for the removal of lecithin from tissues containing 
it, and quite unsuited tor determination of the amount of lecithin in a given tissue. 
Bergell, 3 instead of extracting with ether, used alcohol, and instead of precipi- 
tating with acetone, used an alcoholic solution of cadmium chloride as a precipitant 
in the alcoholic solution of the lecithin, and afterwards broke up the cadmium 
precipitate by boiling with alcohol and ammonium carbonate. 
The yield obtained by Bhrgell by this method was, however, very low, 
amounting for egg yolk to about four per cent., which is less than half that obtained 
by the method to be described in this paper. Also experimentation with 
alcoholic solutions of pure lecithin and precipitation with cadmium chloride has 
proved to us that cadmium chloride is not a complete precipitant of lecithin, a result 
which confirms the observations of Schulze and Winterstein, 4 and shows that this 
salt cannot be used for complete precipitation or estimation of lecithin. On the 
other hand, we have found that precipitation by acetone in ethereal solution is prac- 
tically complete, and in absence of excess of fats and cholestearin, and following on a 
more complete method of extraction from the tissue than is extraction with ether, 
can be made to form the basis for the extraction, separation, and estimation of the 
entire lecithin. 
A consideration of the solubilities of lecithin 01a the one hand, and of the 
bodies present along-jwith it in the tissues from which the problem is to separate it, 
shows that extraction with ether is a bad start to make with the fresh tissue. In the 
first place, the fluid in the tissues is water, or rather saline, which does not mix with 
1. Zeitsch f. physiol chemie (1899), Bd. xxvii, S. 255. Altmann first recommended precipitation of lecithin by acetone 
from concentrated chloroform solutions. Quoted from Hoppe-Seyler's Handbuch dcr physiol. u. pathol. client, analyse (1893), S. 84. 
2. See also E. Schulze u. E. Winterstein, Zeitsch. f. physiol. chemie (1903), Bd. xl, S. 109. 
3. Ber ,1. deutsch. chew. Ges. (1900), 33, SS. 2584-2586. 
4. hoc. cit. 
