140 
Walter Stiles 
Table IV 
Coefficients of Diffusion of Various Substances 
Substance 
Concentration 
in gm.-mols. 
per litre 
Tempera¬ 
ture 
in °C. 
Coefficient of 
Diffusion in 
cm . 2 
-x 10—’ 
Observer 
HC 1 
3-2 
19-2 
sec. 
4-50 
Thovert 
,, 
0-02 
19-2 
2*45 
>> 
HN 0 3 
3*9 
19-5 
2-85 
,, 
h'so 4 
0-02 
19-5 
2*45 
9 > 
2 - 8 5 
18-0 
1-85 
yy 
KOH 
0-005 
18-0 
I * 5 I 
3*9 
13-5 
2-8i 
>» 
0-02 
13-5 
i -95 
,, 
NaOH 
3-9 
12-0 
1-14 
,, 
,, 
0-02 
12-0 
1-30 
y > 
kno 3 
3-9 
17-6 
1-03 
yy 
,, 
002 
iy6 
1-48 
yy 
KC 1 
2-95 
17 *5 
1-85 
,, 
,, 
0-02 
I 7'5 
i *57 
yy 
NaCl 
3’9 
15-0 
1-18 
,, 
0-02 
15-0 
1-09 
Scheffer 
CaCl 2 
1-22 
9-0 
0-83 
,, 
0-0468 
9-0 
0-79 
>> 
k 2 so 4 
ZnS 0 4 
i *5 
10 
0-87 
Schuhmeister 
o *95 
19-6 
0-92 
Thovert 
2*95 
19-5 
0-38 
,, 
MgSO, 
0-025 
19-5 
0-58 
Scheffer 
3-23 
10 
0-31 
Ethyl alcohol 
3*75 
11 
0-52 
Thovert 
,, ,, 
0-05 
11 
0-85 
Heimbrodt 
Glycerin 
i -75 
10-14 
o -35 
,, 
0-125 
10-14 
0-41 
,, 
Citric acid 
0-0303 
4‘5 
0-39 
Scheffer 
Sucrose 
1-97 
18-5 
0-15 
Thovert 
99 
0-97 
18-5 
0-28 
yy 
Albumin 
— 
13 
0-073 
Graham-Stefan 
From the numbers given in this table it will be observed that the 
coefficient of diffusion varies considerably for different substances. 
It is also dependent upon the concentration of the diffusing substance, 
upon the temperature and upon the nature of the medium through 
which diffusion is taking place. In the following discussion, except 
where expressly stated otherwise, the medium is always assumed to 
be water. 
As regards the influence of the nature of the substance on the 
coefficient of diffusion, generally speaking the diffusivity is high for 
electrolytes and substances of low molecular weight, while it decreases 
with increasing complexity of the molecule, being lower for sub¬ 
stances like sugars and very low for colloidal substances. Of the 
commoner electrolytes, acids and alkalies diffuse most rapidly, and 
