251 



showed no effect whatever; 2.5 per cent, sncrose Avith charcoal made from 

 sugar, with himpbhick, with sand: tartaric acid with cloth: tenth-normal 

 sodium thiosulphate with silica. 



Some experiments with sodium chloride and filter paper seemed to 

 indicate negative adsorption, that is, the concentration of the solution was 

 increased, possibly by adsorption of the solvent, and the same result has 

 been reported in some cases by another observer, but in this instance it 

 was found to be due to chlorides in the paper, none of the laboratory 

 supply of filter paper being really free. 



The weights of adsorbing substances and volumes of the solutions were 

 unfortunately not recorded in these experiments. 



The conclusion from this series of experiments is that while adsorption 

 may be very marked in some cases, it is not shown 1)y all solids and all 

 solutions. 



Later, experiments were carried out with Miss Frances DeFrees with 

 a view to ascertaining the relation lietween adsorption and concentration. 

 The adsorber selected was filter paper, and the dissolved substance copper 

 sulphate. The same quantity of the solution was allowed to stand in con- 

 tact with a fixed weight of paper in every case, and titrations were made 

 with potassium cyanide solutions of suitable concentrations on this copper 

 solution and the same solution not treated with paper. The figures ob- 

 tained showed the interesting facts that aliove a certain concentration— 

 about fifth-normal— no adsorption took place; that is, the concentration of 

 the solution underwent no change by contact with the paper. As the 

 concentration was decreased from this point the effect became more and 

 more marked, the amount of copper removed by the paper increasing in 

 absolute quantity up to about twelfth-normal and then decreasing with 

 the concentration to about two-hundred-and-fiftieth-normal, farther than 

 which It could not be followed. The decrease in concentration of 100 c. c. 

 of this solution hy contact with 5 grams of paper amounted to over 25 

 per cent. 



To learn whether both parts of the copper sulphate were equally af- 

 fected a number of determinations were made on the sulphui-ic acid and 

 showed a very close agreement with the copper results, an evidence that 

 the adsorption is of the non-ionized electrolyte and not of the ions in- 

 dependently. 



