EFFKCT OF COPPER SULPHATE. 17 



iiu'iits ol' Israel juicl Ivliiij^'inun " the prescnec of (!0 stj. ciu. of (01)1)01' 

 foil ill 30U cc. of water for twenty-four hours produced plasinal cut- 

 tino' in iS. ht.iu after one and one-fourth hours, in S. (*?v/^'.va after fifteen 

 minutes, and in S. iiiaJHi<cula after thirty minutes. The work of 

 Runun'' shows 1 to 10,000,000 solution still toxic to a few more sus- 

 ceptible cells of "S. hmgdtd. Accordinj^ to Ono, ' weak solutions of the 

 salts of most of the metals encoura<:fe the ji^rowth of alga^ and funt^i. 

 Mercury and copper, however, at ((.oooo,') per cent and o.(H»00l per 

 cent, respectively, distincth' inhi'oit t^rowth. This was the case with 

 Sf!(/e(>cl<>niiiiii, C/t/'oococcu/N, and I*/'ofoeoccu.s. 



In the experiments conducted in this laboratory it has not been pos- 

 sible as yet to include all of the orj^anisms known to pollute water 

 supplies. It is believed, however, that, pending the completion of 

 more extensive work, the data at hand will be of considerable benefit 

 to those who have to deal with contaminated reservoirs. The method 

 of procedure in studying this <|ucstion was to determine roughly the 

 death points of the forms under consideration, using Van Tieghem cells. 

 Accurate solutions were then made, with distilled water, and 200 cc. 

 of each solution was pipetted into an Erlenmycr flask. The algjv, if 

 tihunentous forms, were rinsed; if free-swimming, they were concen- 

 trated by the Sedgwick-Kaftcr'' method from 500 cc. to 5 cc. volume, 

 and this 5 cc. was added to the treated water. The inaccurac}^ due to 

 the addition of the 5 cc. of untreated water to the 200 cc. of treated 

 water was disregarded. Whenever possible, a test of these concen- 

 trations, determined experimentally, was made under natural conditions 

 by treating the pool from which the species under consideration was 

 taken. If this was impracticable, an additional series was carried 

 through in aquaria of 15 liters capacit}", in which were kept goldfish, 

 frogs, minnows, Crustacea, and rotifers. Since in no case was there 

 an appreciable difference in the effect of a concentration upon a par- 

 ticular organism under either natural or artificial conditions, no special 

 record is made of these gross experiments. 



The different species tested may, for convenience, be grouped as (1) 

 those with death points at higher concentrations than 1 part copper 

 sulphate to 1,000,000 parts of water; (2) those with death points between 

 1 to 1,000,000 and 1 to 5,000,000; and (3) those with death points at 

 greater dilutions than 1 to 5,000,000. 



"Israel and Klingman, Virchow's Archiv., 147: 293. 



&Rumm, Beitrage zur Wissenschaftliche Botanik, 1: 97. 



cQno, Journ. of College of Sc, Imp. Univ. Tokyo, 13: 141. 



'^ Whijiple, The Microscopy of Drinking Water, New York, 1899, p. 15. 



