STREAM POLLUTION 
413 
COMPOUNDS OF VARIOUS METALS 
Compounds of many metals are rapidly lethal, because these compounds coagu- 
late and precipitate the mucus secreted by the gills of fishes (Carpenter, 1930) and 
many of the proteins in the living cells. This action has been explained in the dis- 
cussion of the effects of pollutants on fishes (p. 400). In addition, some metallic 
salts, such as ferric chloride, if present in sufficient quantities may increase the acidity 
of the water to a level dangerous for aquatic life and combine this hazard with that of 
the metallic coagulant. 
Since the carbonates and phosphates of many metals are relatively insoluble in 
water, the hardness of waters receiving effluents containing compounds of the heavier 
metals is an important factor in determining the immediate lethality of such effluents 
to fishes, as a considerable portion of these metals may be precipitated from the 
effluent by the salts in the water. This factor has led to much confusion concerning 
the absolute limits of lethality of metallic compounds for fishes, since various ob- 
servers have used different kinds of test water, ranging from distilled to very hard. 
Unless the hardness of the water in question and particularly the amounts of carbon 
dioxide, both fixed and free, be known the limits of lethality of any particular metallic 
compound in any given water are difficult to estimate even though there may be ample 
data on the specific toxicity of that compound. Besides, the factors of synergy 
and antagonism between the metallic compound itself and other compounds in the 
water or effluent which do not precipitate this metallic compound must be considered. 
Examples of this action are presented in table 10 for copper sulphate. 
Table 10 . — Influence of other salts in solution upon the toxicity of copper sulphate to gold fish 1 
Series 
Copper sulphate 
concentration 
Sodium nitrate 
concentration 
Calcium chloride 
concentration 
pH 
Specific con- 
ductivity 
mho X 10' 6 
at 25° C. 
Average survival time 
Ratio by 
weight 
Parts 
per 
million 
Ratio 
by 
weight 
Parts 
per 
million 
Ratio 
by 
weight 
Parts 
per 
million 
Water 
Solu- 
tion 
W ater 
Solu- 
tion 
A 
1 : 100, 000 
10 
7. 1 
4. 0 
<50 
112 
B 
1 : 100. 000 
10 
1:2,000 
500 
7. 1 
5.7 
<50 
806 
C .. 
1:100, 000 
10 
1:1,000 
1, 000 
7. 1 
5. 7 
<50 
1,478 
D 
1 : 100, 000 
10 
1:500 
2, 000 
7. 1 
5.8 
<50 
2,749 
E 
1 : 100, 000 
10 
1:333 
3, 000 
7. 1 
5.8 
<50 
4,020 
F 
1:100, 000 
10 
1:250 
4, 000 
7. 1 
6.0 
<50 
5,413 
G_ 
1 : 100; 000 
10 
1:200 
5, 000 
7. 1 
6.0 
<50 
6,668 
H 
1:100. 000 
10 
1 : 1G7 
6, 000 
7. 1 
6. 4 
<50 
7,734 
J 
1:100, 000 
10 
1 : 143 
7, 000 
7. 1 
6. 2 
<50 
9,013 
K 
1 : 100. 000 
10 
1:125 
8, 000 
7. 1 
6. 3 
<50 
10, 113 
L 
1:100,000 
10 
1:2, 000 
500 
1:20,000 
50 
7. 1 
6.3 
<50 
lj 513 
5 hours 15 minutes. 
M 
1:100,000 
10 
1:1,000 
1,000 
1:20,000 
50 
7. 1 
6.3 
<50 
1,541 
5 hours 30 minutes. 
N 
1 : 100. 000 
10 
1:500 
2,000 
1:20,000 
50 
7. 1 
6.4 
<50 
2,825 
6 hours 30 minutes. 
O 
1:100. 000 
10 
1:333 
3,000 
1:20, 000 
50 
7. 1 
6.5 
<50 
3,984 
9 hours 30 minutes. 
P . 
1:100, 000 
10 
1:250 
4, 000 
1:20, 000 
50 
7. 1 
6.4 
<50 
5,350 
12 hours 30 minutes. 
Q 
1 : 100, 000 
10 
1:200 
5, 000 
1:20,000 
50 
7. 1 
6.4 
<50 
6,573 
12 hours 45 minutes. 
R 
1 : 100, 000 
10 
1:167 
6, 000 
1:20,000 
50 
7. 1 
6.5 
<50 
7,866 
8 hours. 
S 
1:100,000 
10 
1:143 
7,000 
1:20, 000 
50 
7. 1 
6. 5 
<50 
8,763 
7 hours. 
T 
1:100,000 
10 
1:125 
8, 000 
1:20,000 
50 
7. 1 
6.5 
<50 
10,338 
Do. 
IT 
1:333 
3, 000 
7. 1 
7. 3 
<50 
4,221 
( 2 ). 
V 
1:250 
4, 000 
7. 1 
6.7 
<50 
5' 350 
80 hours. 
w 
1:200 
5, 000 
7. 1 
6.8 
<50 
6,620 
37 hours. 
X 
1:167 
6, 000 
7. 1 
6.9 
<50 
7,798 
6 hours 30 minutes. 
1 Glass distilled water was used in these tests. Other conditions as described in table 8. 
3 Survival greater than 4 days, fish apparently unaffected. 
