430 
BULLETIN OF BUREAU OF FISHERIES 
Sulphur dioxide, SO2 
Bleaching works; various chemical industries. Weigelt, Sarre, and Schwab (1885), 10 p. p. m. 
in tap water caused trout to float helpless in 10 minutes; Shelford (1917), 16-19 p. p.m. in tapwater 
killed orange-spotted sunfish, Lepomis humilis, in 1 hour. 
Sulphuric acid, H2SO4. Oil of vitriol 
Pickle liquor from sheet metal and wire factories; waters from coal and iron mines; various 
chemical wastes. Wells (1915), 7.36 p. p. m., in distilled water killed bluegills, Lepomis paUidus, 
in 60 hours, but 3.68 p. p. m. apparently harmless over period of 1 month. M. M. E., 59 p. p. m. 
in very soft water killed goldfish, Carassius auratus, in 1 hour to 1 hour 15 minutes, 138 p. p. m. in 
hard water in 4 hours, 100 p. p. m. in hard water apparently not injurious to goldfish in 100-hour 
exposures; 29 p. p. m. in soft water killed cladocerans, Daphnia magna, in 24-72 hours. 
Tannic acid, C14H10O9 
Tannery wastes; teachings from some barks and sawmill wastes. M. M. E., 100 p. p. m. in 
hard water killed goldfish in 9-20 hours, but 10 p. p. m. apparently not injurious in 100-hour ex- 
posures. 
Tartaric acid, COOH (CHOH) 2 COOH 
Dye wastes; mordant liquors; leather works; various chemical effluents; some winery wastes. 
M. M. E., 1,000 p. p. m. in hard water killed goldfish in 3-4 hours, 200 p. p. m. in hard water not 
injurious apparently in exposures of 100 hours, 100 p. p. m. in very soft water killed goldfish in 3 
hours to 3 hours 30 minutes. 
Thiophene, C4H4S 
Gas wastes. Shelford (1917), 27 p. p. m. in tap water killed orange-spotted sunfish, Lepomis 
humilis, in 1 hour. 
Tin, Sn 2 
See stannous chloride. 
Trade wastes 
At end of this section. 
Zinc nitrate, Zn(NOs)2 
Dilling and Healey (1926) found that tadpoles survived 3-month exposure to 1.89 p. p. m. 
but failed to develop limb buds, that 5.7 p. p. m. killed most tadpoles and that 94.7 p. p. m. killed 
tadpoles quickly. 
Zinc sulphate, ZnSCh. White vitriol 
Wastes from electrolytic refineries of zinc; incrustations developing from exposed zinc sulphide 
ores; mine tailings; several chemical effluents. Carpenter (1927), 404 p. p. m. in distilled water 
killed minnows, Leuciscus phoxinus, in 3 hours 20 minutes; M. M. E., 1,000 p. p. m. in hard water 
killed goldfish in 1-4 hours, 100 p. p. m. fatal to many goldfish in 5 days. 
Trade wastes 
Lethal limits which will be inclusive cannot be defined for sewage and trade wastes because 
sewage and even such specific effluents as Steffens house waste (from certain types of beet-sugar 
refineries) are not constant either in composition or concentration. The effects of colloidal sulphur 
or ferric chloride on fishes and other aquatic animals can be determined under a variety of condi- 
tions which can be duplicated, or the toxicity of any particular sample of Steffens waste, or pickle 
liquor from tin-plate mills, or deazoting fluid from dye works can also be ascertained with accuracy, 
but to attempt to define the minimal lethal concentration or the maximal dilution for all pickle 
liquors from samples obtained at any plant or series of plants is both unsound scientifically and 
unfair to the industry. Already much confusion, often to the detriment of fisheries interests, has 
resulted from the misuse in this connection of various statements in the literature concerning the 
tolerance of fishes for a given number of p. p. m. of a particular waste, when these observations were 
intended to apply to a specific case. 
