ON THE LIESEGANG PHENOMENON IN GELS 371 



that the prevention of precipitation in the intermediate spaces 

 is not due to their action. 



Owing to the increasing dilution of reagent and solute, the 

 layers get more diffuse, and increase in distance apart, as they 

 are formed down the tube. In one experiment with silver 

 bichromate in gelatin, the distances between the strata were : 



'37, '39, "415, '5, '505, '585, '6, -615, and '885 mm. These 

 approach to a G.P. with r = ro68, the terms of which are : 



'37, '395, '4 2 , "45, '5 1 , '55, '5%> '^3, an d '67- As the strata form 

 at the rate of two or three in twenty-four hours, the irregulari- 

 ties are probably due to variations of temperature. 



To compare the distance between the layers with the 

 strengths of the reacting substances, experiments were made 



N N 



with 1 per cent, agar gels containing : (1) — -CaCl 2 , (2) — CaCl 2 , 



N N 



(3) — NaoC0 3 , and (4) — Na 2 C0 3 . About 2N solution of sodium 

 w/ 70 v 20 



N 

 carbonate was poured on (1) and (2), and — calcium chloride 



upon (3) and (4). The distances apart of the strata were : 



These are, roughly, inversely proportional to the molar strength 

 of the gel, and, within the limits of the experiment, independent 

 of the strength of the reagent. The distances should also be 



dependent on the ratio ^. 



F bably by preventing the adsorption of the solute, a too 

 great concentration of the reagent results in the formation of a 

 continuous precipitate. If the reagents react without the for- 

 mation of a precipitate, diffusion takes place regularly, in either 

 direction. Strong ammonium hydrate was poured on a gel 

 containing copper sulphate : the blue colour gradually diffused 



