42 REPORTS ON THE STATE OF SCIENCE.—1917. 
Chevreul deserves honour not only for the pioneer quality of his statements, 
but also for the detailed tabular accounts of his experiments, which gave 
a stimulus to other investigators. 
He was quickly followed by F. F. Runge ?® who confines his researches 
to cotton, discussing first the ‘ combat’ between the water of the bath and 
the fibre for possession of the dye, and thus explaining the decrease in 
rapidity of deposition as the bath nears exhaustion. Mordants he con- 
ceives to be substances which eagerly combine (enter into) the fabric 
to form a substance that in its turn combines with the dye. 
Persoz?° postulates an attraction between the fibre and dye particles 
analogous to inter-molecular forces, but does not suggest true chemical 
combination between dyes and fibre. In 1856 F. Kuhlmann drew atten- 
tion to the nitrogenous nature (‘ azoted fibres ’) of the fibres which readily 
absorb dye, experimenting with pyroxylin and cotton. He suggests that 
the part played by capillarity and adhesion in dyeing is subordinate if 
important, and also makes the remark that ‘a chemical change which 
results in a change of dyeing-capacity may often be a mere re-grouping 
of molecules.’ J. B. Schlossberger™ follows with a little more leaning 
towards the physical theory. P. A. Bolley 72 reverts, after very careful 
research with the microscope into the place and nature of the deposition of 
the dye on the fabric, to the physical theory, finding that the deposition is 
only on the surface with silk and cotton, though partly within the wool 
fibre. His experiments finally lead to the conclusion that the absorption of 
the dye, with or without mordant, is a surface phenomenon entirely 
analogous to adsorption of charcoal, and that the use of the mordant is 
merely to form lakes. But the discovery of aniline colours in 1856 by 
Perkin, and the rapid spread of inquiry into their nature and application, 
emphasised the trend of opinion in favour of the chemists. Schutz- 
berger 23 pointed out that in the dyeing of wool with aniline colours there 
was necessarily chemical action, usually between dyestuff and mordant, but 
does not suggest that the fibre in any way enters into the reaction ; 
he looks on fibres as porous bodies, carriers of the dye. Again the 
physicists prevailed, until E. J. Mills ** reported experiments in the dyeing 
of silk red from a colourless rosaniline solution, which he took to prove that 
the silk actually entered into combination with the dissociated colourless 
rosaniline base. The observation that wool is dyed red from a colourless 
solution of roganiline base was first pointed out by Jacquemin in 1876. 
Mills gives careful tables showing the laws governing the rate of absorption 
of colour from a cold bath, also of various acid and basic solutions, and 
finally for the result of dyeing from mixed dye-baths. 
R. Meyer,”> on the subject of microscopic research into printed cottons, 
doubts whether the fibre enters into composition of a compound with the 
dye or acts as a containing vessel for the latter; he considers that the 
essential factor in true dyeing is that the dye or the materials which 
produce it in the bath should penetrate the fibre, and inside it be changed 
18 Farben Chemie, Pt. 1, 1834, Pt. 11, 1850. 
20 1846, Traité de l’Impression. 
21 1857, Lehrbuch der organischen Chemie. 
22 1859, Kritische und experimentelle Beitrage zur Theorie der Farbere Journal fiir 
praktische Chemie. 
23 1868, Traité des Matiéres colorantes. 
24 Journ. Chem. Soc. 1883, 144; Journ. Soc. Chem. Ind. 1889, 263. 
25 1883, Berichte. 
