86 



Composition of the Atmosphere 



By properly adjusting the stop-cocks a and b the air sample is slowly sent 

 into the potassium pyrogallate pipette and allowed to remain one minute. 

 After being drawn back and forth twice, it is left over the potassium py- 

 rogallate for another minute, again drawn back and forth twice, next sent 

 to the potassium hydroxide pipette three times, and finally into the po- 

 tassium pyrogallate three times. When the air leaves each separate 

 pipette for the last time the level for the potassium hydroxide and the 

 potassium pyrogallate respectively are exactly set. Under these con- 

 ditions there will be a marked difference in the level of the mercury 

 in the pipette B, owing to the absorption of the oxygen. In adjusting 

 the level of the mercury in this pipette, instead of drawing it to the zero 

 point, it is brought back until it remains in the upper part of the grad- 

 uated portion of the pipette. If outdoor air is being analyzed, and the 

 composition is known with considerable exactness, it can usually be set 

 not far from 20.9. Then by communicating with the manometer, and 

 noting whether the oil index moves to the right or to the left, the mercury 

 in the pipette B may be raised or lowered as necessary, without altering 

 in any way the level of the mercury in the pipette A, until a position is 

 finally obtained which indicates constancy in temperature and pressure 

 conditions exactly like those of the air in the compensating pipette A. A 

 reading of the percentage of oxygen is now taken. After turning the 

 manometer stop-cocks, the air is sent into the potassium pyrogallate 

 three times after each reading, and readings are taken until they agree 

 within 0.002 of each other. 



The routine outlined was followed with practically no modification 

 from April 5 up to Nov. 3, 1909. The details of an analysis made on April 

 5 at ll h 45 m a. m. and carried out with this routine are given in table 50. 



Table 50. Results obtained on sample of outdoor air with 

 first routine, April 5, 1909, ll h 45 m a. m. 



Results with first routine. The total results for the first stage in the de- 

 velopment of this method, namely, from April 5 until November 3, 1909, are 

 given in table 51. It should be noted that these residts are not of selected 

 analyses, but include the records of every analysis made during this time, 

 including both good and bad. In the analyses from May 28 to June 3 

 it was necessary to absorb carbon dioxide and oxygen simultaneously, 

 owing to the fracture of the potassium-hydroxide chamber C previously 

 referred to. An examination of the data shows that on the whole there 

 is no material difference between the analyses made of air taken from the 



