6 Nebraska Agricultural Exp. Station, Research Bui. 8. 
two. This agrees with the results as found by Fischer^ for fibrin 
and by Ostwald for gelatin.^ Fischer obtained maximum swelHng 
of both fibrin and gelatin in approximately 0.025 N hydrochloric 
acid and diminished swelling for concentration above this. 
Of special interest is the fact that both lactic and acetic acids 
show concentrations of optimal swelling for gluten. Such an 
optimal swelling of a protein in a *'weak" acid has never before 
been observed. It does not occur in gelatin, fibrin, and the other 
animal colloids thus far studied. The swelling of gluten also 
diminishes much more rapidly with increasing concentration of 
hydrochloric acid beyond the optimal point than does the 
swelling of gelatin or fibrin. It is also of interest that moist 
gluten loses water in the higher concentrations of hydrochloric 
acid, 0.2 N and 0.5 iV. We have established that gluten disks 
lose weight in these higher concentrations of acid because of loss 
of water and not because of ''solution" of the gluten. Examina- 
tion of the surrounding fluids in these higher concentrations of 
acid fails to reveal more than traces of dissolved protein, whereas 
in the lower concentrations where greatest swelling takes place 
considerably more protein is dissolved. When gluten swells in 
dilute acid the disks puff up and take on an appearance somewhat 
resernbling cotton balls, finally becoming transparent, soft, and 
gelatinous. In 0.2 N and 0.5 N hydrochloric acid, the disks do 
not change in appearance or in physical properties except to 
become tougher and more elastic just as in salt solutions. Disks 
which have lost water in 0.5 N hydrochloric acid gain water and 
become soft and gelatinous when placed in more dilute acid. 
Those which have absorbed water to more than double their 
weight in the more dilute acid lose it if placed in 0.5 acid. The 
taking up and giving off of water is, in other words, largely 
reversible. 
When any salt is added to an acid in which a gluten disk is 
swelling, the swelling is much reduced. This is shown in Table 4 
and Figure 2, which is based upon the results shown in this table. 
^ Fischer, Oedema and Nephritis, Sec. Ed., N. Y. (1915), pp. 44, 48. 
' Ostwald, Pfliiger's Arch., 108, 577 (1905). 
