1899] TOXIC EFFECT OF DELETERIOUS AGENTS 387 
From these data we learn that a 24 per cent. aqueous solu- 
tion of KCN deteriorates so that at the end of ten days it has 
but little more than one fourth its former toxic value. Made up 
Wt 
re 
retains but one eighth of its original toxic value. All cultures with 
KCN, reported in this paper, except those noted above, were 
made up within four hours of titration of the stock solution. 
It will be seen by reference to the charts that KCN in 68 
in beet infusion at = concentration and kept ten days longer it 
tion has almost exactly nine times the toxic effect of ionic H. 
KCN in the concentrations used is quite highly ionized (Kohl- 
fausch ’79), but in trying to approximate the toxic value of the 
CN ion, the fact that a certain amount of hydrolysis takes place 
in aqueous solutions of this salt, with a corresponding formation 
of the deadly HCN, must not be overlooked. According to the 
data worked out by Shields (’93) and what we already know of 
the properties of HCN, approximately 15 per cent. of the total 
oxic value of these solutions must be attributed to the HCN 
besent. This would give something under 8H as the value of 
the CN ion. 
KCN retarded germination and early development in all forms. 
o|h this, as with many other agents, those cultures not greatly 
injured soon overcame the effect of the poison and grew and 
i ttuited normally. No marked retardation of fruiting nor unusual 
-tevelopment of mycelium was noted. Sterigmatocystis, in so 
Many cases highly resistant, proved equally sensitive hs (Edo- 
~“Phalum, both being inhibited by —~; and killed by ¢ - 
Kahlenberg and True (’96) found that towards Lupinus it 
tas the value of 1H only. They also show that in the cases of 
Potassium ferro- and ferri-cyanid the iron and CN radical form 
‘“mplex ions, the toxic value of which is far less than that of 
| Ne CN ions, 
Mercuric chlorid.—HgCl, ; 0.0258, 0.287, 0.331. This proved 
. Most fatal compound tested, leading silver nitrate by a narrow 
_argin, 
