STREAM POLLUTION 
409 
In practical pollution work, therefore, any effluent as long as its osmotic pressure 
is greater than 6 atmospheres may be expected to be lethal to fresh-water fishes re- 
gardless of any specific toxic properties. Below this osmotic pressure the toxic, 
chemical, and corrosive characteristics of wastes will be the major determining fac- 
tors in its lethality. Brine wastes, however, often present pollution hazards largely 
because of their osmotic pressures. 
ACIDS 
High acidity is a characteristic of a large number of wastes, so that the action of 
uncombined acid is one of the major problems of stream pollution. In determining 
the lethality of acid wastes, both the actual acidity- — that is, the pH or hydrogen-ion 
concentration of the polluted water carrying acid effluent — and the specific acid in- 
volved must be considered, as acid wastes do not kill merely because of a particular 
degree of acidity. 
In table 8 a summary of an extensive series of experiments on the lethali t,y of 1 1 
acids found in stream pollutants is presented. It is obvious, first of all, from this 
table that it is futile to attempt to designate a given p. p. m. value as marking the lethal 
point for any particular acid as the buffer substances and dissolved salts of the water 
into which acid waste is poured will determine the amount of free acid or hvdrogen- 
ions available. The actual conditions, therefore, presented to aquatic life following 
the addition of a given number of p. p. m. of a particular acid to soft water will be 
quite different from those presented by the same amount of that acid when added to 
hard water, with of course all sorts of intermediate possibilities between these two 
extremes. For example, 134 p. p. m. of sulphuric acid killed goldfish in from 6 to 90 
hours when added to soft water, but were not lethal when added to hard water. 
Table 8.- — Survivals of 700 goldfish in various concentrations of 11 acids found in industrial wastes 1 
Substances 
Concentra- 
tion ratio 
by weight 
Parts 
per 
mil- 
Diluent 
water 
pH 
Specific con- 
ductivity 
mhoXlO -8 
at 25° C. 
Survival time 2 
Constituent of — 
lion 
W ater 
Solu- 
tion 
Water 
Solu- 
tion 
1:70 
14, 286 
4,975 
1, 585 
1,000 
Hard 
8.0 
3.0 
641 
936 
26 to 33 minutes 
Do 
1:201 
8.0 
3. 5 
641 
749 
30 to 36 minutes. 
Do_ 
1:631 
8.0 
4.0 
641 
673 
50 to 60 minutes 
Do 
1:1, 000 
do 
7.8 
4.5 
645 
693 
50 minutes to 1 hour 30 
minutes. 
Do 
1:1,005 
995 
do 
8.0 
4.5 
641 
652 
2 hours to 5 hours 50 min- 
utes. 
Beet-sugar 
Do . 
1:1,077 
929 
do_- . __ 
7.9 
4.6 
641 
662 
wastes. 
Do 
1:2, 365 
423 
do 
8.0 
5.0 
641 
676 
4 hours 45 minutes to 20 
hours. 
Do 
1:2, 871 
s 1:10, 000 
3 1:100, 000 
348 
__ _ do.. __ _ 
8.0 
5. 5 
641 
675 
Do 
100 
__ _do_- . __ 
7.8 
6.8 
645 
675 
Do.. 
10 
do 
7.8 
7.3 
645 
688 
Do 
3 1:1,000, 000 
1:1,000 
1 
___ do 
7.8 
7. 6 
645 
680 
co 
Benzoic acid 
1,000 
do.... 
7.8 
4.8 
666 
593 
j-Ooal-tar wastes. 
Do 
Chromic acid 
1:5, 000 
1:1,000 
200 
1,000 
do 
Very soft 
Hard __ _ 
7.8 
6. 2 
5.9 
1. 4 
666 
<50 
647 
647 
598 
3, 680 
844 
7 hours 16 minutes to co... 
Do 
1:1, 250 
800 
7.8 
5. 4 
Do 
1:2, 500 
400 
do 
7.8 
5.9 
724 
15 hours 18 minutes to 28 
Do 
1:5, 000 
200 
do 
7.8 
6.4 
647 
716 
hours 24 minutes. 
60 hours 24 minutes to 84 
hours. 
[Tannery wastes. 
Do 
1:10,000 
1:10,000 
1:400 
100 
do 
7. 8 
7. 3 
647 
689 
CO 
Do 
100 
Very soft 
Hard 
6. 2 
4. 0 
<50 
6« 
641 
469 
Citric acid 
2, 500 
1,433 
8. 0 
3.0 
841 
Do . 
1:698 
do 
8.0 
3.5 
654 
3 hours to 3 hours 30 min- 
utes. 
Citrus-fruit prod- 
Do 
1:1, 119 
894 
__ __do. 
8.0 
4.0 
641 
542 
ucts wastes. 
Do 
1:1,600 
625 
do 
8.0 
4.5 
641 
494 
