408 
BULLETIN OF BUREAU OF FISHERIES 
SPECIFIC LETHALITY TABLES 
OSMOTIC PRESSURE AND SODIUM CHLORIDE 
Many effluents carry soluble substances exerting considerable osmotic pressure, 
and because of that property are capable when sufficiently concentrated of withdraw- 
ing water from the gills of fishes and from other delicate external organs of various 
aquatic organisms, with the attendant damage to the living cells. High concentra- 
tions of many sorts of pollutants present this danger quite independently of any 
toxic, chemical, or corrosive action they may have on aquatic life. The toxic and 
chemical actions of various salts in stream pollutants may be in part offset by the 
presence of other substances; but the osmotic action of all of the components of the 
mixture may be lethal regardless of their mutual antagonisms or specific toxicities, 
consequently the osmotic pressures of concentrated effluents must be regarded as 
potential hazards until these substances are sufficiently diluted to be within the 
limits of osmotic pressure tolerated by fresh-water fishes. 
Garrey (1916) finds, using the straw-colored minnow, Notropis blennius, as a 
reagent, that fresh-water fishes tolerate an osmotic pressure of the external medium 
equal to that of their own blood if the various salts and substances in the water are 
balanced against each other so as to exclude the specific toxic effects. As the blood 
of fresh-water fishes contains approximately 0. 7-percent sodium chloride, together 
with small quantities of calcium and potassium salts, the limit of osmotic pressure 
tolerated in the external medium by fresh-water fishes is therefore near 6 atmospheres, 
or the approximate equivalent of 7,000 p. p. m. of sodium chloride (common salt) in 
the surrounding water. 
In table 7 data are presented showing the effect of common salt in medium 
water (Mississippi River water) on test goldfish. This water, of course, contained 
small quantities of calcium and magnesium salts, which served to some extent to 
offset the specific toxic action which sodium chloride has in distilled water. (See 
sodium chloride, p. 429.) These river-water tests confirm the work of Garrey (1916), 
as sodium chloride killed quickly in concentrations greater than 10,000 p. p. m., and 
was not lethal in concentrations of 5,000 p. p. m. or less. The survivals in a concen- 
tration of 10,000 p. p. m. sodium chloride in river water ranged from 4 to 7 days, and 
the predicted maximal nonlethal concentration of sodium chloride on the basis of 
osmotic pressure alone in terms of the osmotic pressure of fish blood would be approxi- 
mately 7,000 p. p. m. 
Table 7. — Survival of goldfish in solutions of sodium chloride ; diluent, filtered Mississippi River water 1 
Concentration ration by weight 
Parts per 
million 
pH 
Specific conductivity 
mhoX10-« at 25° C. 
Survival time * 
W ater 
Solution 
Water 
Solution 
1:20 
50,000 
7.8 
7.7 
236 
62, 669 
30 to 40 minutes. 
1:50 
20, 000 
7.8 
7.7 
235 
31, 336 
1 to 2 hours. 
1:67 
14, 925 
7.8 
7.7 
235 
25, 254 
10 to 12 hours. 
1:80 
12, 500 
7.8 
7.7 
235 
25, 200 
24 to 36 hours. 
1:100. 
10, 000 
7.8 
7.7 
235 
18, 772 
4 to 10 days. 
1:200 
5, 000 
7.8 
7.7 
235 
4,156 
CO 
1:1,000 
1.000 
7.8 
7.7 
235 
2, 328 
00 
1:10,000 
100 
7.8 
7.7 
235 
455 
CO 
1:100,000 
10 
7.8 
7.7 
235 
245 
CO 
1 Condition of experiments as described in table 8. 
2 Minimal and maximal survival times as found in these experiments. Infinity sign indicates survival greater than 25 days 
without any apparent injury to fish. 
