412 Journal of Agricultural Research voi. xiii, no. s 



It is impossible to decide from the existing data the exact factors 

 governing the imbibition of water by colloidal gels in acid solutions, 

 but while the hydrogen ion vmdoubtedly plays an important role, it is 

 equally probable that the undissociated molecule and the anion also 

 strongly influence the degree of imbibition. In phosphoric acid the 

 phosphate ions would be strongly adsorbed by the colloid, and such ad- 

 sorption may play a great enough role in increasing imbibition to offset 

 any depressing influence due to the greater concentration of the hydrogen 

 ions. 



However, there can be no doubt, after an inspection of figures i to 3, 

 that there is an inherent difference in the colloidal properties of the 

 different glutens. With lactic and acetic acids the P gluten rises more 

 abruptly and to a higher maximum than with any of the others. The 

 weaker glutens, especially W2 and W^, have a much flatter curve. 



In oxalic and hydrochloric acids (fig. 5, 6) there is a much greater 

 degree of uniformity between the different glutens, but we believe that 

 even here certain differences may be detected, for the curves for the 

 W2 and Wi glutens are again much flatter and have lower maximums than 

 the P or C glutens. 



ANTAGONISTIC ACTION OF SALTS UPON THE IMBIBITION OF WATER 

 BY THE VARIOUS GLUTENS IN THE PRESENCE OF HYDROCHLORIC, 

 OXALIC, LACTIC, AND ACETIC ACIDS 



Tables I to IV and figures 6 to 17 show the imbibition data for the 

 various glutens when certain salts in 0.005 molar concentration were 

 added to the various concentrations of the acids. 



In nearly every instance the addition of the salts decreases the amount 

 of imbibition and also changes the form of the hydration curve so that 

 a higher concentration of acid is necessary to produce maximum im- 

 bibition. There is also a noticeable difference in the behavior of the 

 different glutens. Certain of these differences are recorded in Table X, 

 where the acid concentrations are recorded for the various solutions of 

 lactic and acetic acids at the maximum imbibition of the different 

 glutens. The corresponding figures for oxalic and hydrochloric acids 

 are not included, inasmuch as the curves for these "stronger" acids are 

 much more nearly identical. It is of interest to note that whereas 

 'N/^ acid is the highest concentration of acid causing maximum imbibition 

 in the acids alone, when salts are added there are 15 instances where 

 maximum imbibition is not yet reached at an acid concentration of N/2. 

 The behavior of the different glutens in these solutions is a strong argu- 

 ment for the hypothesis that the physico-chemical properties of the 

 glutens are not identical. This is especially true for the curves for 

 calcium chlorid, magnesium chlorid, and aluminium sulphate. As we 

 pass from P gluten to C gluten and finally to W3 gluten, these curves 

 show less tendency to reach maximums and then decline. The curve for 

 lactic acid plus calcium chlorid is particularly striking. 



