116 Mr Jackson, Molecular Weight of Glycogen. 



The glycogen, thus prepared, was tested for proteids and no 

 trace of nitrogen could be found ; a weighed quantity was ignited 

 in a platinum crucible and no weighable ash was left. It may 

 therefore be assumed that the sample used was free from inorganic 

 salts. 



In determining the molecular weight the cryoscopic method 

 was followed, 30 cc. of water were taken and successive quantities 

 of 2 grams of glycogen were added until 6 grams were present 

 in solution. After each addition the depression of the freezing 

 point was noted and it was thus possible to obtain three readings 

 from each experiment. 



The depressions were extremely small, and the values of the 

 molecular weights deduced from them varied between 9,500 and 

 10,000. 



These results point to glycogen having a highly complicated 

 molecule, which links it closely to the dextrins derived from 

 starch. 



The application of Raoult's method to colloidal solution has 

 been criticised. Recently Lobry de Bruyn (Rec. Tr. Chem. 1900), 

 in considering the size of particles present in colloidal solutions, 

 shews that their diameters deduced from purely physical con- 

 siderations, such as the size capable of polarizing the light 

 scattered by them, are in agreement with those calculated from 

 chemical data, such as the molecular weight determination. There 

 is no distinction between true solution and colloidal solution ; 

 there is no criterion of the homogeneity or heterogeneity of a 

 liquid, and it is possible to pass continuously from undoubted 

 solutions to liquids containing obvious particles in suspension. 



The author would like to express his thanks to Mr W. A. 

 Hoffmann, B.A., of Christ's College, for assistance in this investi- 

 gation, and to the Grant Committee of the Royal Society for 

 funds kindly placed at his disposal. 



