130 Roosevelt Wild Life Bulletin 



At present it is impossible to state the mechanism by which ex- 

 tremely toxic substances like copper sulphate produce marked results, 

 even when greatly diluted. There are, however, certain factors 

 governing this chemical reaction that are of importance, and that 

 were first pointed out by ]\Ioore and Kellerman ('04). They call 

 attention to the fact that the relation between temperature and 

 chemical reaction, so well known in chemical reactions, holds in the 

 toxic effect of copper sulphate, and that smaller amounts will produce 

 the same results when applied during the period when the water is at 

 a miidsummer temperature. Their computations of the amount needed 

 to kill the algae are based upon a standard temperature of 15° C. 

 (59° F.) and they recommend an increase or decrease of 2.5 per cent 

 in the amount of copper sulphate for each degree Centigrade below 

 or above the standard temperature. 



The chemical constitution of the water, both organic content and 

 temporary hardness, affects the reaction, and copper sulphate proves 

 less toxic in hard waters and in those rich in organic matter. Moore 

 and Kellerman ('05) suggest a 2 per cent increase in the amount of 

 copper sulphate for each ten parts per million of organic matter, and 

 a .5 per cent increase for each ten parts per million of temporary 

 hardness. 



The question of introducing a poisonous substance like copper 

 sulphate into drinking water at once aroused interest in the problem 

 of the chemical reactions of this substance with surface waters ; and 

 especially in the question of whether it remains in solution or is pre- 

 cipitated out. Experience has shown that in ordinary or hard waters 

 the copper sulphate is precipitated out within a few days, while in 

 soft waters it may remain for some time. Ellms ('05) has suggested 

 the following reaction to account for the precipitation of the com- 

 pound from natural waters : 



2 CUSO4 + 2CaH2(C03)2=CuC03.Cu02H2 + 2 CaSOi +3 CO2+H2O 



Calcium Basic copper 



Bicarbonate Carbonate 



The basic copper carbonate formed is soluble to a certain extent, 

 especially if there is carbon dioxid in the water. Carbon dioxid is 

 generally present as a result of respiration of organisms in the 

 water, or there may be a small amount produced by the reaction sug- 

 gested above. Following the formation of the basic copper car- 

 bonate there is a change to copper hydrate, an insoluble compound, 

 which is then precipitated to the bottom of the lake : 



CUCO3.CUO2H2 + H2O = 2 CUO2H2 4- CO2 



In the hard waters with which Ellms worked 70-95 per cent of the 

 basic copper carbonate was converted into copper hydrate by the end 

 of three hours, and at the end of twenty-four hours no trace of 

 copper compounds remained in solution. He also noted that this 

 second reaction was affected by the organic content of the water, and 



