1896 | TOXIC ACTION OF DISSOLVED SALTS IIk 
46. VALERIANIC ACID. 
(Begun January 15, 4 P.M.; closed January 16,,3 P.M.) 
Concentration 
m. mol. per liter Length Remarks 
1800 19.0™™ dead 
aie 16:5." “ 
s200 28.0 “ alive 
eee 28.5 sé ‘“ 
From table 42 it appears that the lupines survive in a solu- 
tion of formic acid containing 455 gm. mol. per liter, the same 
concentration as in the case of the strong mineral acids. Accord- 
ing to Ostwald’s determination, formic acid is dissociated to the 
extent of 35.85 per cent. when one gm. mol. is present in 1024 
liters. At 6400 it would be much more highly dissociated. 
From the result it would appear that dissociation is nearly com- 
plete at this high dilution, for the critical concentration is that 
obtained in case of the strong mineral acids. Whether this is 
true or not can be better decided after the effect of sodium 
formate on the seedlings has been studied. Table 43 shows that 
the radicles can bear much more acetic acid than formic. Acetic 
acid is not as strongly dissociated. Propionic, butyric and val- 
erianic acids (tables 44 to 46) show the same critical concen- 
tration, 4y!,5 gm. mol. per liter. Ostwald’s measurements show 
that these acids at 1024 are dissociated to approximately the 
Same degree ; and, as they are closely allied chemically, one 
would expect them to have the same effect on the roots. The 
content of hydrogen ions of the solutions is nearly the same, 
and the undissociated parts together with the anions would have 
about the same effect. Acetic acid is a little more strongly dis- 
*ociated than the last named acids ; the fact that nevertheless the 
Seedlings will bear a greater concentration shows that it is not 
merely the contact of hydrogen ions that comes into considera- 
tion here, but that the action of the undissociated acid and 
the anions makes itself felt. 
Glycollic acid is somewhat more strongly dissociated than 
