468 MINNA E. JEWELL 



siphon which is drawn to a capillary tube at the end. The flow 

 of the acid is regulated by the size of the capillary tube. The 

 acid drops from the siphon into the separatory funnel, through 

 which it passes to the bottom of the 10-liter mixing bottle, where 

 it is thoroughly mixed with the water before entering the experi- 

 mental jars: O.IN H2SO4 was used. The acidity of the water 

 could be regulated by counting the number of drops of acid per 

 minute and regulating the flow of water through the mixing 

 bottle accordingly. 



The distilled water 



In some preliminary experiments ordinary distilled water 

 obtained from the Department of Chemistry was used. This 

 water is condensed in a copper condenser, and passes through 

 block-tin pipes. It was found not only to be very toxic to tad- 

 poles, but to vary in its effect from day to day, so that tadpoles 

 might live several days in water taken from one bottle, and die 

 in a few hours in water taken from another. The same water 

 redistilled in glass supported the life of tadpoles of Bufo lentig- 

 inosus Le Conte through metamorphosis. These results are in 

 accord with the findings of Bullot ('14), and Powers ('18 b), 

 who attributes the toxic effect of ordinary distilled water to 

 traces of colloidal copper taken up from the condenser. Powers 

 has shown that a goldfish may live fifty-one days in water redis- 

 tilled in glass, but succumbs quickly if the minutest trace of 

 colloidal copper be added to the water. 



The water for all of the experiments was condensed in a 6-foot 

 Jena glass condenser attached to the second tank of the water- 

 boiling apparatus mentioned above. It was then aerated for 

 twenty-four hours by a stream of air previously passed through 

 sulphuric acid and calcium hydroxide wash bottles. This distilled 

 water was neutral to rosalic acid and neutral red. An analysis 

 of the water kindly made by the analyst of the State Water 

 Survey was as follows : 



