Comparative Air-Analyses 



111 



Table 70. Analyses made at the Nutrition Laboratory of air collected in the subway, 



in New York City. 



The results of this series of experiments have a particular value, inas- 

 much as they show clearly that a decrease in oxygen is accompanied by an 

 approximate increase in carbon dioxide. While the measurement of car- 

 bon dioxide has been taken as an index of good or bad ventilation, the fact 

 that the proportion of oxygen is actually lowered by an increase in the 

 carbon dioxide has never before been clearly demonstrated. As a result 

 of this study, however, knowing both the constancy of oxygen in outdoor 

 air and the sources of carbon-dioxide production, and knowing also that 

 with the carbon-dioxide production there must likewise be an oxygen 

 consumption, we can safely state that for every one-hundredth per cent 

 of increase in carbon dioxide there will be approximately one-hundredth 

 per cent decrease in oxygen. 1 It will be seen, therefore, that since there 

 are a number of simple and accurate methods for determining carbon 

 dioxide, the time-consuming and complicated determinations of oxygen 

 are entirely unnecessary, as the determination of the percentage of car- 

 bon dioxide in the air establishes the approximate percentage of oxygen. 



ABSORPTION OF OXYGEN BY POTASSIUM PYROGALLATE. 



Since the constancy of the oxygen content of the air has been demon- 

 strated in this research, it has been possible to make a more accurate 

 study than heretofore of the conditions affecting the absorption of oxygen 

 by potassium pyrogallate. Many investigators have experimented with 

 potassium pyrogallate as an absorbing agent for oxygen; but inasmuch as 

 there appeared to be fluctuations in the oxygen content of the air, they 

 have sought for the maximum absorption capacity and minimum produc- 

 tion of carbon monoxide without attempting to control the absorption 

 of oxygen. Particularly confusing has been the fact that the potassium 

 hydroxide as found on the market varies greatly in its water content, 

 the amount ranging from 5 to 25 per cent. 



To investigators on this subject, the experience of Haldane and Hem- 

 pel has been of the most interest. As already stated, the use in this 

 research of Haldane's saturated solution of potassium hydroxide for dis- 

 solving the pyrogallol did not seem wise with so delicate an apparatus as 

 ours. Should there be a complete solidification of the reagent in chamber 

 D, considerable time would be required to get the solution again in con- 



x The one inexplicable phenomenon is the abnormally high percentage of carbon 

 dioxide found in the air of Greenland by Krogh. 



