ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 39 
Mortier, W., ‘ Coll.,’ 1916, 15, 330, 356, 385, 452. 
‘Humussiure und Gerbsiiure.’ 
Tbid., ‘ Coll.,’ 1916, 15, 179. 
‘Die Theorie der Peptisation pflanzliche Kolloide.’ 
Prooter, H. R., and Witson, J. A., ‘ J.S.C.1.,’ 1916, 35, 156, and ‘ L. Coll.,’ 1916, 2. 
56. 
“The action of salts of hydroxyacids upon chrome leather.’ 
Tbid., «T.C.8.’ 1916, 109, 1327. 
‘The Theory of Vegetable Tanning.’ 
Nrnovn, E., ‘L. Coll.,” 1916, 2, 178, 190. (Eng. abst., 227.) 
“Tannage & lalun.’ 
Bennett, H. G., ‘ L. Coll.,’ 1916, 2, 85. 
“ Analysis of limed pelt.’ 
Ibid., ‘ L. Coll.,’ 1916, 2, 106. 
“The acidity of tannery liquors.’ 
Woop, J. T., and Law, D. J., ‘J.S.C.I.,’ 1916, 35, 585. 
‘ Note on the unhairing process.’ 
GENERAL REVIEW AND BIBLIOGRAPHY OF DYEING. 
By P. E. Kine, Lecturer in Dyeing, University of Leeds. 
The Present State of Development of the Theory of Dyeing, with special 
reference to colloidal and electrical hypotheses and phenomena leading 
thereto. 
In the present stage of the evolution of an adequate theory to explain 
the phenomena of the dyeing process, four somewhat conflicting theories 
prevail :— 
The mechanical or physical theory, 
The chemical theory, 
The colloid-diffusion and adsorption theory, 
The electrical theory. 
The two former were long the cause of energetic discussion between 
their respective upholders, the two latter have been developed since the 
beginning of the present century, and are to be looked upon, less as parallel 
theories to the first two, than as more scientific attempts to supplement 
and correlate, in the light of later physico-chemical discoveries, the 
phenomena observed and partially explained by the older theorists. 
The upholders of the mechanical theory? looked upon it merely as 
an adsorption phenomenon, of the dyestuff particles in the fibre; the 
second group took for granted a chemical combination between fibre and 
dye. The holders of the first view based themselves primarily on the 
analogy which subsists between dyeing and the absorption of dyes by 
animal charcoal, More modern investigations by Justin-Mueller, how- 
ever, indicate that pure carbon absorbs only very little dyestuff. The 
decolourising effect of charcoal is connected with the presence of organic 
nitrogenous compounds, which are produced by the combustion of protein 
substances. The upholders of the chemical theory of dyeing, which 
may be described as the salt-formation theory, base their views upon 
the fact that the fibres, especially wool and silk, which by hydrolysis 
give amino-acids, contain salt-forming groups and produce actual salts 
with the dyestufis, which, as is well known, contain acid and basic groups. 
At present the most prominent upholder of the purely mechanical 
1 P, Sisley, ‘ Augenblicklicher Stand unserer Kenntnisse tiber die Theorie der 
Farbung,’ Chem. Zeit. 1913, 1357, 1379. 
