ENVIRONMENT AND REGENERATION 



467 



The flow of air through the water was regulated by passing 

 it through capillary tubes drawn to a fine point, and the air 

 pressure was kept relatively constant by means of a mercury 

 manometer made by bending a U at one end of a 5-foot glass 

 tube, and attaching it at the end of the air line. Mercury was 

 then poured into the tube until a pressure was reached at which 

 air would bubble through the jars at the desired rate. 



Daily O2 determinations were made on water from each jar 

 by the Winkler method. Samples for these determinations were 



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u 



^ 



^ 



^ 



\^ 



u 



\ 



10 



12 



i:«==0 



11 



Diagram 1 Apparatus for securing a series of low concentrations of oxygen. 

 1, inlet for oxygen-free water; 2, aspirator bottle containing acid; 3, syphon; 4, 

 mixing bottle; 5, inlet of air line; 6, 8 and 10, experiment jars; 7 and 9, aerating 

 jars; 11, beaker; 12, manometer containing mercury. 



collected by introducing a Powers' sampling bottle (Powers, 

 '18) between two jars, and allowing the water to siphon through 

 it for fifteen minutes. 



As has been mentioned above, the oxygen-free water from the 

 boiler is strongly alkaline. Where neutral water was desired, this 

 was remedied by means of the acidulator (upper left of figure 1) 

 which consists of a 12-liter aspirator bottle placed in a large earthen- 

 ware milk pan, with the • upper opening securely stoppered. 

 The acid in the pan stands at the level of the top of the lower 

 opening in the bottle, thus giving a constant pressure in the 



