EFFECT OF BOG WATER ON SWELLING 97 



tions of solutions were made in such manner as to test the effect 

 of previous history on the behavior of a biocolloid. Sections of 

 agar-oat-protein 0.18 mm. in thickness swelled 972% in twelve 

 hours at 17 to 19°C. and reached a total of 1233% at the end 

 point in one hundred and eight hours which are equivalent to 

 results previously attained and hence afford a fair basis of com- 

 parison with the following, in which a trio of sections swelled 

 2361% in distilled water at the end point in seventy-two hours. 

 Replacement of the pure water with swamp water was followed 

 by a slow shrinkage which however amounted to only 36% of 

 the original volume. No swelling agent yet tested has been 

 found to reverse the action of another solution so fully as to 

 bring the dimensions of the sections down to the dimensions 

 which might be attained in the second agent alone. 



Sections of a biocolloid consisting of 90 parts agar, 10 parts 

 of bean-protein, to which 0.8% of nutrient salts had been added, 

 0.18 mm. in thickness were now swelled in swamp water at 18 

 to 20°C. The increase was measured at the end of sixteen 

 hours, at which time the total swelling was 1082%. The swamp 

 water was now replaced with hundredth-molar citric acid — 

 potassium nitrate for thirty-six hours during which time no 

 appreciable change was registered. Replacement of this solu- 

 tion with swamp water was followed by a resumption of the 

 swelling which carried the thickness of the sections to 1388% 

 of the original which is greater than that attained in the simple 

 continuous swelling in swamp water. 



Swamp water is high in salts and it is probably this feature 

 to which its influence on swelling is due. A test parallel to the 

 above was made in which the sections were first swelled in a 0.5% 

 nutrient solution in which the salts are somewhat more concen- 

 trated than in the swamp water. A swelling of 888% took place 

 in seventeen hours, at which time the pen of the auxograph 

 was tracing a horizontal line. Replacement of the nutrient 

 solution with the acidified potassium nitrate solution was fol- 

 lowed by a very slight swelling. When the salt solution was re- 

 placed by swamp water an increase of 333% followed in forty 

 hours. The two tests were parallel except that the initial treat- 





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