Abstract

Heats of dyeing have shownl 2that decreasing the temperature from 25°c to 0°c decreases the proportion of dye acid taken up by collagen at equilibrium. This result is the opposite of those obtained hitherto in dyeing all other substrates. This difference in behaviour could be due to the neglect of factors such as aggregation and activity coefficients of the dyes and swelling of the fibre. In order to obtain further information on the relative importance of these factors, the very simple system, hydrochloric acid-collagen, which differs from the dye-collagen system in the size of the anion, has been investigated more fully than heretofor&. Not only have the pH, hydrogen ion concentra tion, and chloride ion concentration been determined directly at equilibrium in the outside bath for different ratios of hydrogen chloride to collagen, but the swelling of the collagen has also been measured. All this has been done at two temperatures. 0°c and 25°c. The results have been interpreted both on the Gilbert-RideaP and the Donnan-Procter-Wilson 5-8theories and, although both theories give a reasonable account of the experimental results, over the region above pH l8 the former gives the better fit. The fact that no serious difficulties were experienced in interpreting the hydrochloric acidcollagen system, and that a small negative heat of reaction was found, implies that the deviations of the acid dye-collagen system are con nected with aggregation and/or activity effects.