ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 21 
more particularly in connection with the condensation of gases upon 
metallic and other solid surfaces (investigations of Langmuir and others). 
This is merely illustrative, but it is sufficient to emphasise the point 
referred to. 
A further object of the Committee is to render available as far as is 
practicable the information on applied colloid chemistry which is believed 
to exist among chemical technologists at the present time, but which from 
its possibly unco-ordinated nature is not regarded as suitable for publication 
through the ordinary channels. It is hoped that those possessing such 
‘incidental’ information, as well as those whose information regarding 
various special technical colloid problems is of a more systematic nature, 
will see their way to communicate with the Secretary (Muspratt Laboratory, 
University of Liverpool), so that the Committee may be able to consider 
the question of publication of such material as it considers suitable. In the 
present state of the subject it is felt that more will be gained by co-operation 
of this kind than by isolated investigation ; and further it is believed that 
much may be made public without detriment to individual interests. 
It will be obvious that under the present exceptional conditions the sub- 
joined Report is of a preliminary nature only. 
As regards classification according to scientific subject, one subject only, 
namely, the Viscosity of Colloid Systems, is dealt with. As regards classi- 
fication according to technical processes and applications generally, the 
following subjects are treated :— 
1. Tanning. 
2. Dyeing. 
Fermentation Industries. 
Rubber. 
Starch, Gums, Albumin, Gelatine, and Gluten. 
Cements. 
. Nitrocellulose Explosives. 
. Celluloid. 
. Physiological and Bio-chemical Subjects. 
It is proposed to deal with other branches of colloid chemistry in next 
year’s Report. 
OI OVE 09 
VISCOSITY OF COLLOIDS. 
By Emit Hatscuex, Sir John Cass Technical Institute, London. 
General Review. 
An excellent general survey of the subject as it stood at that time 
is given by the General Discussion by the Faraday Society in 1913. The 
most important advance since then is the proof, by v. Smoluchowski, 
that the electric charge on suspensoid particles contributes to the viscosity 
of systems containing such particles, and the numerical expression deduced 
by him for this increase. 
The Kinstein formula, according to which the increase in viscosity 
is simply proportional to the aggregate volume of suspended spheres, 
has again been tested by Humphrey and Hatschek on a suspension of 
starch grains (average diameter 3) in a mixture of carbon tetrachloride 
and toluene. ‘The increase in viscosity was found to be more than linear 
for concentrations between 2 and 6 per cent.; in addition, the viscosity 
