Effect of Salts and Acids on Biocolloids and Cell-masses. 41 



that in the 0.0002 M solutions here, as in some of the trials previously 

 made, the swelling is very high, probably even higher than that in dis- 

 tilled water. 



Swellings of the agar-oat-protein mixture for 24 hours at 15 C. gave 

 the results shown in table 24 in di-potassic phosphate (K^HPC^) . 



The sections in the 1 M solution were sealed 

 by the glass triangle, which was pressed too 

 closely on them, with the result that swelling 

 progressed very slowly to a defective total. 



Di-potassic phosphate. 



Distilled water . . 



2 M 



1 M 



0.1 M 



.01 M 



.005 M 



.001 M 



.0002 M 



00005 M.. 



p. ct. 



156 



125 



625 



806 



1,563 



1,719 



1,889 



1,964 



If the results of the swelling in the di-potassic 

 phosphate were plotted as a graph, it would be 

 seen that the steepest part of the curve would 

 lie in the region between the concentrations of 

 0.01 M and 0.005 M. The graph of the potas- 

 sium chloride would be a much more regular 

 figure. The steepest part of the graph of the 

 results with calcium chloride would probably 

 lie between 0.01 N and 0.005 N, the steepest 

 part of the graph of calcium nitrate would probably be in the region 

 between 0.02 N and 0.002 N, and the steepest part of the line express- 

 ing the falling-off of the retarding action of potassium nitrate would 

 be between 0.05 N and 0.005 N. 



The breaks or discontinuities in the rise of the curve of imbibition 

 total led to the belief that some errors had crept in, and repetitions 

 were made with concentrations from 0.01 M to 0.000005 M. The 

 additional experiments were for the most part symmetrical with each 

 other, although it is not allowable to contrast the separate items of the 

 swellings of two different lots of material. The ground at first taken, 

 that in minute quantities some of these salts might cause a swelling in 

 excess over that in distilled water, still lacks confirmation. It is a 

 matter, however, that should be tested with great care, as such re- 

 actions for sections of plants are included in my records. 



The swelling in various concentrations of a salt supposedly depends 

 chiefly upon the acid ion, although the action of the basic ions is not 

 actually excluded. The above tests were made in solutions varying 

 from 4 M to 0.5 M, which are far too concentrated to be of direct 

 biological interest. A more dilute series of potassium salts in 0.01 M 

 and 0.001 M solutions was made up and the swelling of sections of 

 agar 90 parts and peptone 10 parts, 0.22 mm. in thickness, were made 

 at 15 C. The tests were closed at the end of 24 hours, and although 

 some slight increase was still in progress, the relations of the various 

 preparations were identical with those which might be expected of 

 the end-points. (Table 25.) 



According to Hofmeister, as cited by Taylor, swellings of gelatine 

 in chlorides and nitrates should be greater than in the citrates and 



