94 REPORTS ON THE STATE OF SCIENCE.—1917. 
The Viscosity and Electro-chemistry of Protein Solutions. WoLFGANG Pav. P. 54, 
The Rate of Coagulation of Al(OH), Sols as measured by the Viscosity Change. 
H. Frevonpuicu and C. Isnizakr. P. 66. 
The General Theory of Viscosity of Two-Phase Systems. E. Hatscumr. P. 80. 
Does Poiseuille’s Law- hold good for Suspensions? M. Rotumann. ‘ Pflueger’s 
Arch. d. Physiol.’ 1914, 155, 318. 
On the Influence of Viscosity and Surface Tension on Biological Phenomena. 
J. Traust. ‘Internat. Zeitschr. f. phys.-chem. Biol.’ 1914, 1, 275. 
The Importance of Viscosity Measurements for the Knowledge of Organic Colloids. 
J. Scurrera. ‘ Internat. Zeitschr. f. phys.-chem. Biol.’ 1914, 1, 260. 
The Viscosity and Hydration of Colloidal Solutions. Svanrr Arrurntus. ‘ Med- 
delanden frin K. Vetenskapakad. Nobelinstitut.’ 1916, 8. (Criticism of the 
hydration values calculated by H. Chick for various proteins by Hatschek’s 
emulsoid formula. By applying his well-known logarithmic formula Arrhenius 
finds hydration values of the same order as for hydrated salts.) 
The Viscosity and Hydration of Colloidal Solutions. E. Hatscrrx. ‘ Biochem. 
J.’ 1916, 10, 325. (Reply to the foregoing. If Arrhenius’s formula is applied 
to sols in organic solvents, it leads in a number of cases to negative solvatation 
factors, which are physically meaningless.) 
The Viscosity of Colloidal Solutions. E.HatscnEexK. ‘ Proc. Phys. Soc. Lond.’ 1916, 
28, Part rv. 250. (Controversial.) 
The Viscosity of Suspensions of Rigid Particles at different Rates of Shear. Eprra 
Houmpsrey and E. Hatscnex. ‘ Proc. Phys. Soc. Lond.’ 1916, 28, Part v. 274. 
(The viscosity of suspensions containing from 2 to 6 per cent. by volume of 
particles averaging 34 diameter is a function of the rate of shear. At no rate 
examined does this suspension show the linear increase of viscosity postulated 
by the Einstein-Hatschek formula.) 
The Viscosity of Colloidal Solutions. A. v. Smonucnowsxt. ‘ Koll. Zeitschr.’ 1916, 
18,190. (Review of reasons why the Einstein formula fails to agree with measure- 
ments, especially those obtained by the capillary viscometer. Proof that the 
electric charge increases the Stokes resistance factor and therefore the viscosity 
of suspensoids.) 
COLLOID CHEMISTRY OF TANNING. 
By Professor H. R. Procter, University of Leeds. 
General Review.* 
The conversion of skin into leather is an art dating back many thousand 
years, and the group of phenomena now classed as capillary or colloid has 
also been long known, though the relation of the two is a matter of modern 
knowledge. Under these circumstances it is difficult to know where 
to begin the discussion, and the question is further complicated by the 
wor : of the present writer and his pupils, who have recently shown that 
much which has been attributed to the surface-action which is implied 
in the name ‘ capillary chemistry ’ is really subject to more general laws, 
and can be fully explained by mass action, electro-chemical attraction, 
and osmotic pressure. The title must therefore be taken, with a wider 
meaning than its etymology would imply, to include much of physical 
chemistry, complicated, however, by structure and the special properties 
of colloids. 
The skin is constituted of collagen (probably a polymerised anhydride 
* Among the abbreviations employed in this Section are the following :—Coll. 
= Collegium ; J.A.L.C.A.=Journ. of the American Leather Chemists’ Association ; 
L, Coll. = London Collegium, Jan. 1915 to June 1917; 7.0.8, —Transactions of Chemical 
Soctety (London). 
