THE CALIBRATION OF THE OSTERHOUT RESPIRATORY 

 APPARATUS FOR ABSOLUTE QUANTITIES OF CARBON 



DIOXIDE. 



By G. H. PARKER. 



{From the Zoological Laboratory of Harvard University) 



(Received for publication, April 11, 1922.) 



In the course of a piece of work on the amount of carbon dioxide 

 produced by sea anemones it was found desirable to use the respira- 

 tory apparatus devised by Osterhout (1918), and as it was necessary 

 in this work to determine the absolute quantity of carbon dioxide 

 eliminated by these animals, an attempt was made to calibrate this 

 apparatus for such determinations. The method finally adopted 

 seems to be of enough general importance to justify a brief statement 

 of it. 



The Osterhout apparatus consists of a closed system in which the 

 air is made to circulate by means of a pump. The air passes from a 

 chamber, in which the organism is confined and in which conse- 

 quently the carbon dioxide is produced, either directly to a glass tube 

 containing an indicator in solution or indirectly to this tube through 

 a U-tube filled with fragments of sodium hydroxide. In the direct 

 course the air containing the carbon dioxide is forced to bubble 

 through the indicator solution, thus causing it to change its tint. 

 In the indirect course the air is relieved of its carbon dioxide by 

 contact with the sodium hydroxide, and, after purification, it is 

 bubbled through the indicator thus washing out the contained 

 carbon dioxide and bringing the indicator back to its original color. 

 From the tube containing the indicator the air returns by a direct 

 course through the pump to the chamber in which the organism is 

 confined. A figure of the apparatus is given by Osterhout (1918). 

 In taking readings with this apparatus the time in seconds required 

 for the indicator to change from one tint to another as compared 

 with standard solutions of known pH value is recorded and the rate 



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