899] TOXIC EFFECT OF DELETERIOUS AGENTS 315 
- compared with the checks ; while < the limiting culture, failed 
to fruit in six days. 
With HCl a sixth form, Rhizopus nigricans, was tested. Like 
its near relatives the mucors, it makes very unsatisfactory growth 
ina liquid medium, and was therefore discarded. Its resistance 
to HCl proved to be practically the same as that of Gidocepha- 
um, The limiting culture of Aspergillus, = , developed a 
 tumber of abnormal conidiophores, each bearing 1-4 sterig- 
mata, on the sixth day. 
In the case of HCl, as in the case of all other acids tested, 
 mattempt was made to determine the relative toxic value of the 
anion. The potassium salt was used. This salt becomes highly ' 
| lonized into K and Cl ions in moderately concentrated solutions. 
Ina : KCI solution 84 per cent. of the salt is thus ionized. In 
. 20a concentration of HCl 89 per cent. is ionized ~ H 
—{dClions. (Kohlrausch, ’85.) In the former we have K and 
(lions and some KCl; in the latter, H and Cl ions and some 
| HCL It is evident therefore that the essential difference 
+ 
; tetween these solutions is the replacing of H in the latter by K, 
am the HCl by KCl in the un-ionized portion. The significant 
Pomt is that the concentration of Cl ions is practically the same 
i : both. The : HCI solution is fatal to the spores of Aspergil- 
: *S while © KCI solution has practically no injurious influence. 
: ay this fungus germinates, grows, and fruits normally in a! 
a ei of double this concentration of KCl. Hence we ee 
i as Cl ion is relatively harmless to this mold. Similar tests | 
' 2a its low toxic value to all the molds used. 
: ES lute toxic value of ionic Cl, and other weakly see 
New > however, very difficult to determine. ae this ee 
a es ould be remembered that the potassium sips a 
4 inn Sie are, although highly, far from being a “/ 
; at the concentrations permitting germination of mo 
