38 



ILUNOIS BIOLOGICAL MONOGRAPHS 



[158 



solutions and that colloids are very toxic and tiiat the amount of coUoid in 

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

 Miyake (1916) foiind 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 CUCI2 tested. 

 Mengarini and Scala have shown that nimierous metals, like copper and alumi- 

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

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

 tin leads, was due possibly to the colloidal CuO X H2O and Sn02 X H2O. Ringer 

 (1883) foimd that goldfish would five from 46 to 54 hours in distilled water. 

 Bullot (1904) foimd 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 all toxic to about the same extent. 



Three sets of experiments were nm 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 Uved 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 

 colloidal solution of copper was prepared in water distilled in ordinary glass 

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

 water a smaller amount of colloidal copper was added and the goldfish lived 

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

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



