68 Studies of Diffusion through Rubber Membranes [Sept. 



ing to the method described by Koch. For the dialysis tests the 

 Solutions of the lecithan Compounds were evaporated to dryness at 

 38° and the residues triturated with ether. The extracts were fil- 

 tered, and the filtrates placed inside of rubber bags and dialyzed 

 against ether for thirty-seven days. The dialysates were tested 

 weekly to see if the substance combined with the lecithan had 

 diffused. 



Compounds of lecithin with glucose, lactic acid, strychnin, digi- 

 tonin, salicin, urea, creatin, Creatinin, and caffein were prepared. 

 It was found that the glucose and lactic acid dialyzed completely, 

 the strychnin, digitonin, and salicin dialyzed partially, while urea, 

 creatin, Creatinin, and caffein did not dialyze at all.^ 



It was thought that some of the various substances which did not 

 diffuse might do so in the presence of a considerable amount of dif- 

 fusible material, but on dialyzing various mixtures of the above- 

 named indiffusible substances with varying amounts (up to 15 

 grams), of neutral fat, fatty acid, cholesterol, or olive oil, no diffu- 

 sion of lecithan occurred. 



When Solutions of lecithans are subjected to dialysis by the 

 method described above, they take up a great deal of ether, and the 

 volume of liquid in the bag is greatly increased. We have demon- 

 strated that lipins exert strong osmotic pressure. ( See page 59. ) 



We have also placed ether Solutions of lecithans with cholesterol 

 and fat in closed rubber bags suspended in Soxhlet extractors. 

 Soxhlet extraction in the usual way failed to remove lecithan from 

 the bag under these conditions. These findings favor the develop- 

 ment of a method for the thorough removal of impurities from 

 lecithan Solutions. 



It is perhaps superfluous to add that the results already mentioned 

 may be obtained by placing the Solution to be tested outside the 

 rubber bag and allowing dialysis to take place into pure ether con- 

 tained in the bag. 



III. SUMMARY OF GENERAL CONCLUSIONS 



I. Most lipins, chief among them, fat, fatty acid, soaps, cho- 

 lesterol, cholesterol-esters, lipochrome, and various other ether-sol- 



• Boas and Rosenbloom : Loc. cit. 



