Dandeno — Relation of Mass Action to Toxicity. 447 



tions, the difference being greater and greater as the amount of 

 solution increases. So that beyond a certain limit of concen- 

 tration, no matter how much ionic hydrogen be present, this 

 hydrogen is prevented from acting on the radicle by the mere 

 presence of the mass of water. This is probably because diffu- 

 sion is so very slow. The corn seedling theoretically should 

 resist 1, 2, 4, 8 CC of HC1 in the 4 dilutions given in Table III, 

 if diffusion were perfect. But it does actually resist 1, 2J, 12, 

 inf., Table III, so that the difference in quantity due to mass 

 action is represented by the differences between the pairs of 

 numbers in the series thus, — 0, J, 8, inf. Now, in ^/8192 the 

 lupine or the corn will counteract the harmful ions as fast as 

 they come in contact with the radicle, so that the dilution at 

 which the seedling lived in 25 cc may be said to be the dilution 

 where diffusion and vital activity are balanced. The limit of 

 resistance, therefore, for corn is l cc of w/1022 ; and of 25 cc 

 7i/8192. 



It has been pointed out (3, 1. c. p. 90) that lateral roots 

 which develop after a seedling is placed in a test solution may 

 live and grow even though the radicle itself be killed. Kah- 

 lenberg and True suggest that this is due to a power of accom- 

 modation, but this is quite probably not so, because in a number 

 of experiments with seedlings which had withstood one solution, 

 an attempt was made to have them grow in a solution a grade 

 stronger, or in the same solution in greater quantity, but with- 

 out success. Seedlings showed no power of accommodation. 

 It is more probably due to the fact that the radicle has already 

 partly neutralized the solution, as appears in Tables X and XI. 



The strongest solution of carbonic acid (H 2 C0 3 ) which it was 

 possible to obtain was n/111 by actual titration test. Seedlings 

 of corn and lupine stood this concentration readily, but the pea 

 did not. With the largest quantity of solution used (25 cc ) the 

 pea survived in ?i/513 but died in ?i/342. 



H 2 0O 3 , according to the theory of dissociation, may dissociate 

 into H ions and CO„ ions, or possibly into H ions and HC0 3 

 ions, more probably the latter, reasoning from such data as we 

 have concerning NaHC0 3 . Neither case can be true, speaking 

 in the language of the theory of electrolytic dissociation, because, 

 if there were H ions present in such quantity as is indicated by 

 a dissociation into H ions and CO, ions, then it would be as 

 toxic as H 2 S0 4 , but, from those experiments, it can scarcely be 

 one-fiftieth as toxic. The other alternative method of dissocia- 

 tion can not account for this either, for a similar reason. These 

 results are in opposition to the theory of dissociation. 



The experiments with sodic carbonate show that the corn 

 seedling endures a solution of n/128 in 25 cc . From the side 

 of the theory of dissociation this substance should permit 



