20 REPORTS ON THE STATE OF SCIENCE.—1917. 
Colloid Chemistry and its Industrial Applications.—First Report 
of the Committee, consisting of Professor F. G. Donnan 
(Chairman), Professor W. C. McC. Lewis (Secretary), 
Dr. E. F. Arnmsrrone, and Mr. A. 8. SHorTER. 
INTRODUCTION. 
Tur Committee was formed with the object of compiling information 
regarding the advances which have been made in capillary and colloid 
chemistry with special reference to industrial processes. For this purpose 
it is essential to take a broad view of the term ‘colloid.’ The Reports 
which it is proposed to issue will refer to the more important scientific in- 
vestigations published in recent years as well as to those possessing a more 
immediate technical bearing. The Committee has been fortunate in ob- 
taining the collaboration of a number of specialists in various branches of 
the subject who have undertaken the work of compilation. The advantage 
of this mode of procedure lies in the fact that the necessary selection and 
presentation of material has been carried out by those particularly qualified 
to deal with the various sections concerned. ‘To these gentlemen the Com- 
mittee would express its deep sense of obligation. 
As regards the classification and division of the whole, two methods 
present themselves: first, a classification according to the nature of the 
property, principle, or phenomenon concerned, based on the recognised 
divisions of the science of colloid chemistry, e.g., Coagulation, Viscosity, 
Adsorption, Peptonisation, &c.; secondly, a classification in terms of the 
various technical processes themselves, each of which involves in general 
more than one scientific principle, e.g., the process of Tanning, which in- 
cludes Adsorption, Coagulation, ‘Membrane Equilibria,’ &c. Both of 
these modes of classification have been adopted. This naturally involves 
a certain amount of overlapping, but it is felt that the disadvantage is not 
serious. It is hoped that this treatment of the subject-matter will not only 
be comprehensive, but will serve at the same time to illustrate the close 
connection which exists between scientific principles and technical practice. 
At the present time many of the operations in technical colloid chemistry 
are largely empirical, the scientific basis being unknown or only imperfectly 
understood. One of the objects which the Committee has had in view is to 
emphasise the existence of this state of affairs. It is clear that the present 
position demands a vigorous prosecution of scientific research over the 
entire range of colloid chemistry. 
The marked differences of opinion which exist at the present time in 
regard to various colloid problems are themselves evidence of the relatively 
undeveloped state of the subject. As an illustration we might instance the 
phenomenon of Adsorption. On the one hand, we have the capillary view 
first stated quantitatively by Gibbs, a view which at the present time 
occupies a very strong position especially as regards liquid surfaces. On 
the other hand, we find the capillary idea dropped and the concept of 
valency beginning to take its place as an explanation of the phenomenon, 
