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ILLINOIS BIOLOGICAL MONOGRAPHS 



[158 



solutions and that colloids are very toxic and that the amount of colloid in 

 the solution is not in proportion to the concentration of the salt in solution. 

 Miyake (1916) found 1/75000 N. AICI3 was toxic to the growth of rice seed- 

 lings which he attributed to colloidal AICI3. Robin (1914) showed that the 

 toxic activity of colloidal sulphur was much more intense than that of other 

 forms of sulphur. The maximum survival time of the goldfish in ordinary 

 distilled water was about the same as that in the most dilute CuClo tested. 

 Mengarini and Scala have shown that numerous metals, hke copper and alumi- 

 num, form colloidal solutions in distilled water at room temperature. The 

 toxicity of the distiUed water, since it was distilled in copper stills with block- 

 tin leads, was due possibly to the coUoidal CuO X H2O and Sn02X H2O. Ringer 

 (1883) found that goldfish would live from 46 to 54 hours in distilled water. 

 BuUot (1904) found that the survival time of Gammarus was shorter in water 



distilled in copper than in ordinary glass, Jena glass, quartz glass, and plati- 

 num. The latter were aU toxic to about the same extent. 



Three sets of experiments were run to test the supposition that a colloidal 

 solution was responsible for the short survival time of the goldfish in ordinary 

 distilled water. 1. The goldfish hved 36 days in distilled water after an 

 electrolyte (0.025 N. NaCl) had been added to precipitate the' colloid. 2. 

 The goldfish Uved 30 to 52 days in water distilled in ordinary glass. 3. A 

 coUoidal solution of copper was prepared in water distiUed in ordinary glass 

 by arcing copper wires under the surface of the water. To one quantity of 

 water a smaUer amount of coUoidal copper was added and the goldfish lived 

 about 2820 minutes. To another a larger amount of colloidal copper was 

 added and the goldfish Uved only about 900 minutes. Thus the greater toxic 



