Permeability 147 
potassium chromate diffuses more slowly through 4 per cent, 
gelatine than through water, and Coleman (1888), examining the 
diffusion of a number of electrolytes in gels, also concluded that the 
presence of the jelly brings about a retardation in the rate of diffusion. 
Hagenbach (1898) came to a similar conclusion in regard to the 
diffusion of gases in gelatine. Henri and Calugareanu (1903), from 
observations on the diffusion of a number of dyes in water and 1, 3 
and 5 per cent, gelatine, concluded that the rate of diffusion was 
the same through the gelatine as through water if the former had 
not set to a gel, but that if this had taken place, the rate of diffusion 
was slower. Bechhold and Ziegler (1906) concluded that electrolytes 
and non-electrolytes diffuse through gelatine and agar gels more 
slowly than through water. 
Oholm (1913) compared the diffusion of potassium chloride from 
a normal solution into gels of 2, 5 and 10 per cent, gelatine. His 
results, summarised in the accompanying table, indicate very clearly 
the retarding effect on diffusion of the gelatine. 
Table IX 
Diffusion of Potassium Chloride from a Normal Solution into 
Gels of Gelatine of Various Concentrations 
(Data from Oholm) 
Coefficient of Diffusion 
Concentration 
of Gelatine 
in per cent. 
Kind of Gelatine 
at 20 0 C. in 
cm. 2 
- x 10- 6 
sec. 
2 
Kahlbaum (golddruck) 
1-52 
5 
„ 
I *44 
10 
,, ,, 
131 
2 
A brand from Dundee 
1-50 
5 
,, ,, ,, 
1-41 
10 
, , , . ,, 
1-28 
If these numbers are compared with those given in the preceding 
table it will be observed that, as Oholm points out, a gelatinous 
body affects the diffusion of an electrolyte in just the same way as 
any other non-electrolyte. Unpublished observations of Stiles and 
Adair indicate that the presence of gelatine decreases the rate of 
diffusion of sodium chloride progressively with increase in concen¬ 
tration of the gelatine. There can be no doubt that the coefficient of 
diffusion of electrolytes is less in gels of gelatine than in water. 
Voigtlander (1889) made a study of diffusion in agar-agar gels 
varying in concentration from 1 to 5 per cent, and found that the 
4—6 
