391 



water, serves when the bottle is laid on its side to show any undis- 

 solved substance lighter than the water, thus making the method later 

 applicable to the light slightly soluble constituents of waste. The 

 temperature of such experiments was usually 20°C. 



2. TOXICITY OF WASTK AND TAR. 



The toxicity of waste from the Champaign plant varies so that a 

 general statement as to the toxicity can hardly be made. In general 

 the greater the amount of tar the more toxic the waste. The most 

 toxic sample contained much tar. Eight liundredths of a cc. of the 

 waste was introduced from a Mohr pipette into four liters of water 

 in a four liter bottle. The water was shaken until all the wastt had 

 gone into solution excepting a slight tarry film on the sides of the bot- 

 tle near the surface of the water. It is impossible to say how much 

 of the substance actually went into solution, but assuming that half of 

 it did, it may be safely said that ten to twenty parts per million of 

 this waste killed a 4-5 gram Lcponiis hiimilis in an hour, while twice 

 that amount killed such fishes in from ten to thirty-five minutes. An- 

 other sample with less tar killed fishes of the same size in five iiours 

 when 1,000 parts per million were present. 



A small amount of tar w^as rubbed on the sides of several full 

 grown Lepoinis hiimilis and the fishes left in open acjuaria ; all died 

 in from one to nineteen hours. 



A small amount of tar was rubbed in the mouths and on the sides of 

 several suckers and orange-spotted sunfishes in open aquaria. All died 

 in from one to nineteen hours. IMarsh ('07) found tar very toxic to 

 perch and bass. 



Aerating and boiling removed toxic constituents of the waste. For 

 example, a sample of waste was treated as follows: 



1. Fresh waste was added to 99 times its volume of aerated 

 water as quickly as possible, and the small space above the water in 

 the large bottle was filled with illuminating gas. 



2. Some of the same waste was aerated by pouring from one 

 beaker to another for three minutes. This was added to 99 parts of 

 water and corked. 



3. Some of the same waste was boiled vigorously for several 

 minutes, until all odor of ammonia was removed, and added to 99 

 parts of aerated water. 



The efifect of these treatments is illustrated by the following ex- 

 periment which is one of many. A liter of each of the three kinds of 

 waste was put into each of three battery jars and 4-5 gm. orange- 

 spotted sunfishes placed in them. They survived as follows : 



