The Colloidal Swelling of Wheat Gluten. 
25 
The weight of dry gluten may be obtained after drying at 110°C. 
to constant weight. As a check, nitrogen determinations may be 
made on the dry gluten. 
The explanation for some of the facts brought out by our 
experiments is not at present evident. We have repeatedly 
demonstrated that gluten, prepared by washing the starch from 
flour with distilled water, does not change in weight when placed 
in salt solutions even when the concentration of the latter is as 
high as N ;2 (2.9 per cent). On the other hand, larger amounts 
of wet gluten are obtained by washing the starch from flour 
with salt solutions of concentrations varying from 0.1 per cent 
to 2.5 per cent than are obtained when distilled water is the 
washing agent. Furthermore, our figures show this increased 
weight obtained with the salt solutions to be due to hydration 
of the gluten. In other words, when salt solutions are the wash- 
ing agents gluten swells more (absorbs more water) than when 
distilled water is the washing agent. These facts are not in 
harmony with the results of our experiments on the swelling of 
gluten as reported in the first part of this paper. When pieces 
of gluten are simply placed in salt solutions, for several hours 
even, swelling is inhibited. 
These facts do not in any way modify our conclusions in 
regard to the effect of acids and salts on the character of loaf 
obtained when the flour is made into bread. The different results 
are without doubt due to the difference in conditions in the two 
experiments. When moist gluten is allowed to remain in con- 
tact with a solution, conditions are not the same as they are 
when gluten is washed in a continuous stream of that solution. 
In the latter case, the gluten is washed in the fingers so that the 
solution permeates the whole mass; and since the solution is 
constantly changing, other substances besides starch are washed 
from the mass. The first condition is more nearly like the one 
which obtains in the bread-making process. 
While no doubt the different results are due to the difference in 
conditions, still the complete explanation is not apparent. It is 
possible that washing with salt solution changes the degree of 
dispersion of the gluten in such a manner as to favor increased 
water absorption. The facts present a problem in colloidal 
chemistry which requires further study. The authors plan in 
the near future an extended research in this field. 
