412 
BULLETIN OF BUREAU OF FISHERIES 
detrimental effects which may act synergistically with the specific toxic actions of 
the substances producing such deviations in pH must be expected. 
In this connection, it must be pointed out that although the lethality limits of 
acid wastes as given here are applicable to immediate or intermittent pollution the 
cumulative effects must also be considered. When goldfish were kept in water at 
pH 4.5 produced by addition of small quantity of sulphuric acid, this amount of 
sulphuric acid, although tolerated for a few days without apparent injury to the 
fish, seemed definitely detrimental to goldfish in exposures longer than 2 weeks, even 
though some fishes can tolerate pH 4.5 in the natural habitat when this degree of 
acidity is produced by carbon dioxide and acids from decaying vegetation in bog and 
swamp lakes. It may be necessary, therefore, to add sulphuric and other acids to 
the lists of those producing specific toxic effects when long-time experiments in 
progress are completed. 
Table 9 presents data concerning the effects of acids on daphnia comparable to 
those given in table 8 for fishes. In the cases of daphnia which do not produce 
volumes of protective mucus to remove or in part buffer down the acid in the effluents 
to which they may be exposed, the maximal acidity of the solutions in which there 
was any survival by daphnia was around pH 5.4. It is significant in this connection 
to recall that the isoelectric point at which many proteins found in living tissue are 
precipitated is pH 5.5. The daphnia tests, therefore, suggest strongly that were 
fishes unprotected by mucus the lethal hydrogen-ion concentration for acids in 
general would be near pH 5.5, and explain the detrimental effects of acid wastes to 
the stream faunae in general even though the particular concentration may be sur- 
vived by some fishes. In waters less acid than pH 5.5 the same relative lethalities 
of the various acids were found for daphnia as for fishes. 
Table 9. — Survivals of l+,500 Daphnia magna in various concentrations of 5 acids found in indus- 
trial wastes 1 
Substance 
Concentra- 
tion ratio by 
weight 
Parts per 
million 
pH 
Specific conduc- 
tivity mhoXlO" 6 
at 25° C. 
Survival time 
Final 
percent 
mortality 
W ater 
Solution 
Water 
Solution 
1:1, 333 
750 
7. 4 
4 0 
470 
516 
100 
Do— . 
1:2, 000 
500 
7. 4 
4 6 
470 
491 
do— 
100 
Do 
1:5' 333 
188 
7. 4 
5. 0 
470 
461 
_do 
100 
Do 
1:8, 000 
125 
7. 4 
5. 4 
470 
460 
24 to 72 hours 
75 
Citric acid . _ 
1:2, 666 
375 
7.6 
4.0 
425 
532 
1 to 2 hours 
100 
Do 
1:4, 210 
248 
7. 6 
4. 6 
425 
491 
2 to 17 hours 
100 
Do 
1:5, 405 
185 
7.6 
5. 0 
425 
490 
10 to 17 hours 
100 
Do 
1:8, 340 
120 
7. 6 
5.5 
425 
466 
24 to 72 hours 
40 
Do 
1:12, 500 
80 
7. 6 
5. 9 
425 
440 
OO 
o 
Hydrochloric acid. . .. 
1:14, 545 
69 
7. 4 
4.0 
452 
660 
1 to 4 hours. . .. 
100 
Do 
1:15, 384 
65 
7. 4 
4. 5 
452 
650 
do 
100 
Do 
1:16, 667 
60 
7.4 
5.0 
452 
614 
4 to 17 hours 
100 
Do 
1 : 17, 777 
56 
7. 4 
5. 4 
452 
595 
80 
1:3’ 470 
288 
7. 6 
4. 0 
442 
493 
100 
Do 
1:4, 280 
234 
7.6 
4.5 
442 
463 
do 
100 
Do 
1:5, 230 
191 
7. 6 
5. 0 
442 
443 
6 to 48 hours. _ 
100 
Do 
1:5, 880 
170 
7.6 
5. 5 
442 
441 
26 to 72 hours ... 
66 
Sulphuric acid. . 
1:20, 000 
50 
7.3 
3. 5 
324 
610 
1 to 3 hours. .. 
100 
Do 
1:26,667 
38 
7. 3 
4.0 
324 
184 
24 hours 
100 
Do 
1:33, 333 
30 
7. 3 
4. 5 
324 
389 
100 
Do 
1:34, 479 
29 
7. 3 
5. 0 
324 
381 
24 to 72 hours 
100 
Do 
1 : 50, 000 
20 
7. 6 
6. 5 
375 
387 
0 
Do 
1 : 100i 000 
10 
7.6 
7.3 
375 
375 
do 
0 
Do. . 
1:1, 000, 000 
1 
7. 6 
7. 6 
375 
375 
0 
Do 
1:10, 000! 000 
0.1 
7.6 
7.6 
375 
375 
do 
0 
1 Standard daphnia, 5 days old, from parthenogenie clones were used. For each dilution 150 animals were carried in glass jars 
containing 4 liters of the solution, and these jars held at 25° C. in constant temperature chamber. The diluent was soft water (see 
p. 406) from the same source as that in which the stock colonies of daphnia were living. A control of 150 animals in 4 liters of this 
water without test substance was maintained for each series. 
