ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 57 
Wm. Harrison and Haldane Gee™* proceeded now to carry out their 
experiments testing this electrical theory and found it to explain phenomena 
observed better than the adsorption theory, which Lewis" had discredited 
on the grounds that it demands a decrease in amount of dye adsorbed under 
increase of temperature. These authors claim that it is always an 
electrical phenomenon: if the dye be colloid, then coagulation results 
from neutralisation of charge ; if not colloidal, then it is ionised in solution 
and deposited by contact-electrification charges acting on the ions. 
They discovered a most important phenomenon, ?.e., that the maximum 
negative charge attained by wool, silk, and cotton was at 40°. This is 
undoubtedly strong evidence in favour of an electrical phenomenon, as 
Brown" found that wool absorbed most basic colour at about 40°. 
Harrison refers to the physical constitution of the fibres, as the surface 
(on which the charge rests and to which the dye-particles wander to fix 
themselves) is greatly increased by the porosity and irregularity of the 
fibre. He suggests that the dye-particles, if very large, will not fix on silk 
so well as on wool or as on cotton (this being the order of increasing size of 
their pores) ; by this theory Harrison also explains the adsorption and 
fixation of the direct cotton-colouzs. 
In his dyeing experiments various salts, &c., are added, none of which 
tend to retard coagulation or to decrease the size of the particles, but rather 
the reverse. The dye should, therefore, be fastest dyed without salts, and 
this Harrison finds to be the case. Also, as an increase in temperature 
decreases the size of the particles, it should increase the fastness of the 
resulting dyeings. This also he finds to be true. 
Feilmann expressed his ideas of dyeing similarly to those of Gee and 
Harrison, 2.¢., that the dye was attracted electrically by the oppositely- 
charged fibre. He also asserted that the ion of the dyestuff penetrated the 
fibre more or less deeply, and was retained either because the fibre acted 
as a protective colloid or because chemical action took place between the 
ion and the fibre. 
COLLOID CHEMISTRY IN THE FERMENTATION INDUSTRIES. 
By Prof. Appian J. Brown, University of Birmingham. 
BIBLIOGRAPHY. 
“Studies on the Coagulation of Starch.’ A, FurnBacu and J. Woiry. (‘J. Inst... 
Brewing,’ 1904, 10, 216.) 
On the coagulation of soluble starch by amylocoagulase, an enzyme existing in 
the germinated seeds of barley and other cereals. 
“The Diastatic Coagulation of Starch.’ A. Fernpacu and J. Wourr. (‘Comp. 
Rend.’ 1904, 139, 217. Abst. ‘J. Inst. Brewing,’ 1905, 11, 190.) 
* Anti-amylocoagulase.’” A, FrrnBacu and J.Woxrr. (‘Ann. Brass. et. Dist.’ 1906, 
9, 513. Abst. ‘J. Inst. Brewing,’ 1907, 18, 184.) 
“Colloidal Properties and Spontaneous Coagulation of Starch.’ E.Fouarp. (‘ Comp. 
Rend.’ 1908, 147, 931. Abst. ‘J. Inst. Brewing,’ 1909, 15, 330.) 
46 Trans. Faraday Society, 1910, April (Journ. Munic. Sch. Lechn. Manchester, 
vol. iv., 1911, pp, 131-154), Paper (Harrison) Journ. Soc. Dyers and Col., 1911, p. 279. 
They append to their paper a translation of Pelet’s tables of affinity between 
colloid-coagulation, contact-electrification, capillary ascent and dyeing, as does also 
Zsigmondy (Kolluid Chemie, p. 229). 
46 Phil. Mag. 1908 (6) 15, p. 499. 
47 Journ. Soc. Dyers and Col. 1901, p. 92. 
