344 
ROBERT AARON STEINBERG 
majority are salts of heavy metals. The salts of the heavy metals, when 
the anion is that of a strong acid, hydrolyze in aqueous solution, resulting, 
as a rule, in increased acidity of the solution. Of the seventeen ions ([H+] 
is included) contained in this list, thirteen are reported as acting in this 
manner. The apparent exception in the case of the ferrous and manganous 
ions disappears on recognition of the ease with which their solutions are 
oxidized when in contact with the atmosphere. Ferric and manganic (14) 
ions behave similarly to the other heavy metal ions, as is generally reported. 
In the case of only two of the ions listed above (F~ and SiQ-s") does the 
hydrolysis of the majority of their salts lead to decreased acidity of the 
solution. In the case of the fluorides, the ammonium salt (NH4F) from 
what can be gathered from data at our disposal, appears to hydrolyze in 
aqueous solution (14) with increased acidity due to the formation of 
HNH4F2. 
A. niger 
Compounds Reported as " Stimulants " 
Compound 
Max. Yield 
Control 
Optimum of 
** Stimulant " 
Author 
i Hydrolysis at 25° C. 
(27) 
Solution 
Acid to Lit- 
mus (40) 
ZnS04 
4-69 /I-55 
O.I mgZn/L 
Javillier (21) 
m/5 = 0.0075 
+ 
MnS04 
0.982/0.610 
10 g.Mn/L 
B. & J. (4) 
None? 
0 
CdS04 
0.750/0.277 
o.oi mgCd/L 
Lepierre (29) 
m/5 =0.017 
+ (*) 
BeS04 
0.490/0.281 
o.oi mgBe/L 
" (30) 
+ (66) 
U02(N03)2 . 
" (31) 
+ 
HgCl2 
0.630/0.341 
0.0013% 
One (49) 
m/256 = i.43 
+ 
MnCU 
0.380/0.245 
0.004% 
Richards (57) 
+ 
C0SO4 
0.805/0.550 
0.002% 
m/32 =0.015 
+ (*) 
C0SO4 
0.872/0.297 
0.014% 
Ono (49) 
+ 
NiS04 
0.785/0.200 
0.033% 
Richards (57) 
m/32 =0.044 
+ (13) 
NiS04 
0.404/0.262 
0.014% 
Ono (49) 
+ 
FeS04 
0.892/0.275 
0.132% 
Richards (57) 
None? 
0 
CUSO4 
0.352/0.218 
0.003% 
Ono (49) 
m/5 =0.05 
+ 
NaF 
0.640/0.330 
0.002% 
Richards (57) 
-(66) 
NaF 
0.325/0.199 
0.0025% 
Ono (49) 
LiCl 
0.410/0.280 
0.016% 
Richards (57) 
? 
Li2S04 
0.560/0.235 
0.5% 
? 
LiNOs 
0.428/0.300 
0.008% 
+ (*) 
NaaSiOs. . . . 
0.575/0.350 
0.004% 
-(66) 
Al2(S04)3. . . 
0.260/0.205 
0.002% 
+ 
Fe2(S04)3... 
0.6+/0.1 + 
Steinberg 
+ 
Acids 
0.3 /0.13 
+ 
* Tested the Kahlbaum compounds personally. In the case of the lithium salts only 
the nitrate was available. 
I have repeated Richards' (57) experiments with sodium silicate. The 
results of my experiments are negative. They are tabulated below (experi- 
ments 17 and 18). 
17. The effect of adding sodium silicate to the culture medium. 
Strain W, ii 
Control Na2Si03 (Kahlbaum) 
0.066 g. 0.002% 0.073 g- 
O.Q35 0.008 0.073 
0.086 0.098 0.078 
0.084 
0.068 
