223 
According to the researches of H. J. WATERMAN and myself 
described in these Proc. (80 Dec. 1911 and 30 March 1912) 
retardation is usually associated with a strong solubility in fat or 
with a too large concentration of hydrogen ions. 
Now, boric acid is much more readily soluble in water than in 
olive oil and is moreover an exceedingly feeble acid so that these 
two properties cannot, therefore, explain to us why borie acid so 
very much retards the growth of penicillium glaucum as we have 
indeed observed. 
The formation of compounds with the polyaleohols which play 
such an important rôle in the living beings, compounds which can, 
moreover, be much more strongly acid than boric acid itself, offers 
a very simple explanation of the powerful action of this apparently 
so innocuous substance. 
Under the influence of the development of the chemistry of the 
colloids, the origin of physiological processes has been perhaps 
searched for a little too much in purely physical phenomena: diffu- 
sion, change in surface tension, discharge of negative-charged colloids 
by positive ions and reversely, ete. Undoubtedly, all these actions 
play an exceedingly important rôle, but in many cases a chemical 
phenomenon is involved; it is like this with boric acid and so it 
will be, presumably, with the toxic action of many metals (I further 
refer to a communication from H. J. Warrrman and myself in the 
“Folia microbiologica’’). 
The question whether the strong action of some of the hydroxyl 
compounds is associated with an easy ring formation, as surmised 
by van ’r Horr, has, as yet, been discussed by me only casually. 
Last year, Fox and Gaver (Trans. Chem. Soc. 1911, 1075) have 
succeeded in isolating mannitoboric acid and in preparing some of 
its salts, but as it appears from the analytical figures that there is 
present one molecule of water in excess of that required for the 
5-ring closure, the configuration still remains uncertain. 
As pyrocatechol causes a very strong increase of the conductivity 
I have endeavoured to obtain pyrocatecho-borie acid._ Although we 
have not succeeded in doing so, we have yet managed to prepare 
a series of readily erystallizable complex salts some of which are 
characterised by a very slight solubility, so that they may, presumably, 
serve for the quantitative separation of boric acid. 
A full description of these salts, also of the experiments mentioned 
above, which have been carried out mainly by Mrs. N. H. Siewerts 
VAN Rexsema, C. E. Kramer and J. D. Ruys, will be given later. 
Delft, May 1912. Org. Chem. Lab. Techn. High School. 
