REACTIONS OF FISHES TO ATMOSPHERIC GASES 



209 



solution we must either increase the total pressure, decrease the 

 temperature, or substitute a more soluble for a less soluble gas. 



TABLE 1 



Showing the distribution and solubility of atmospheric gases 



2. EXPERIMENTAL CONTROL OF GASES IN SOLUTION 



The two methods commonly employed in the control of gases 

 in solution in water are (a) The reduction of gas content by 

 boiling or by vacuum pumps, and (b) The increase of some one 

 gas by bubbhng it through water, 



a. Gases used 



The analyses of the commercial gases were made with the 

 Hempel ('02, chap. 3) apparatus. The carbon dioxide was 

 absorbed with 33| per cent potassium hydroxide; the oxygen 

 with yellow phosphorus except when it constituted more than 

 50 per cent of the total, in which case alkahne pyrogallol was 

 used. Oxygen and carbon dioxide in solution were determined 

 by the methods given by the Committee on Standard Methods 

 of Water Analysis of the American Health Association ('05, pp. 

 72-77), and by boiling. Boilings were made in a boiler like that 

 described by Birge and Juday ('11, p. 7), which holds two liters. 

 The gas obtained was analyzed by absorption and was corrected 



