51 



Kruyt, H. R. 'Current-Potential of l^ieotrolytic Solutions.' ' Verslag. Akad. 

 VVetenschappen," 23, 252 (1914). 



' Electrical Cliarges and the Limiting Values for Colloids,' ibid., 23, 200 

 (19U). 



' Current Potentials and Colloid Stability.' ' Kolloid-Z.', 22, 81 (1918). 

 Lewis, W. C. McC. ' A System of Physical Chemistry.' (Longmans, Green & Co.) 

 Paui,i, W., and Matxjxa, J. ' A Physicochemical Analysis of Colloidal Ferric 



Hydi-oxide.' ' KoUoid-Z.' 21, 49 (1917). 

 Powis, F. ' The Relation between the Stability of an Oil Emulsion and the 

 Potential Difference at the Oil-Water Sui-face Boundary and tlie Coagulation 

 of Colloidal Suspensions.' ' Z. physik. Chem.' 89, 18(3 (1914). 



' The Influence of Time on the Potential Difference at the Surface of Oil 

 Particles Suspended in Water,' Ibid., 89, 179 (1914). 



' Negative CoUoidal Ferric Hydroxide.' ' J. Chem. Soc' 107, 818 (1915). 

 ' Transference of Electricity by Colloidal Particles.' ' Trans. Faraday Soc.', 

 (1915). 



• The Coagulation of Colloidal Arsenious Sulfide by Electrolytes and its 

 Relation to the Potential Difference at the Surface of the Particles.' ' J, 

 Chem. Soc,'. 109, 734 (1916). 

 Shoeter, S. A. ' The Capillary Layer as the Seat of Chemical Reactions.' 



'J. Soc. Dyers & Colourists,' 34, 136 (1918). 

 Taylor, W. W. 'The Chemistry of Colloids' (Longmans, Green & Co.). 

 Thomas, A. W., and Gakaed, I. D. ' The Fallacy of Determining Electrical 



Charge of Colloids by Capillarity.' 'J. Am. Chem. Soc' 40, 101 (1918). 

 Wilson, J. A. 'Theory of Colloids.' 'J. Am. Chem. Soc' 38, 1982 (1910). 

 ZsiGMONDY, R. ' Theoretical and Applied Colloid Chemistry.' (Jolm Wiley & 

 Sons. 1917 ) 



IMBIBITION OF GELS— PART I. 



By John Arthur Wilson, Chief Chemist, A. F. Galhm «& Sovs Co., 



Milwaukee. 



One of the commonest methods of demonstrating what is meant 

 by imbibition is to immerse a thin sheet of ordinary gelatin in water. 

 In less than an hour the gelatin 'will be found to have become miJch 

 swollen by absorbing, or imbibing water. After the first hour, the 

 rate of swelling noticeably decreases, and the volume papers to 

 approach a definite limit. The amount of water taken up can be 

 determined by weighing the gelatm before and after swelling. The 

 absorbed water behaves much as though it were dissolved in the 

 gelatin, and it can be removed hy washing the gelatin with absolute 

 alcohol. As the water is removed, the volume of the gelatin diminishes, 

 approaching its volume before swelling. During imbibition heat is 

 evolved, which has often been referred to as heat of swelling. Probably 

 this is resj)onsible for the repeated statement that the application 

 of heat -will repress the swelling of gels. On the contrarj^ rise of 

 temperature causes greater swelling, which seems to indicate that 

 the liberation of heat is not due to swelling, but to some other cause, 

 which the WTiter believes to be chemical combination between the 

 gelatin and a small portion of the absorbed water. Procter has 

 shown that the degree of swelling is also dependent upon the previous 

 history ot the gelatin. He prepared three solutions containing 

 5 per cent., 10 per cent., and 20 per cent, respectively of gelatin and 

 allowed them to set. He then dried the jellies and, after ^\eighing, 

 allowed them to soak in water for seven days. The sample with the 



D 2 



