84 Composition of the Atmosphere 



The apparatus described was first set in order in the latter part of 

 February 1909. After considerable preliminary experimenting with room 

 air and with air from a respiration chamber, a series of analyses of out- 

 door air was begun on April 5, 1909. The first routine employed for de- 

 termining the carbon dioxide and oxygen is as follows: 



Outline of first routine. It is necessary in the first place to make sure 

 that all the capillary tubes communicating with the different reservoirs 

 are filled with nitrogen and not with air. For this purpose a blank analy- 

 sis is made in which quantitative accuracy is not required. In making 

 this analysis, the air in the apparatus is first passed into the potassium 

 pyrogallate several times until thorough absorption of both carbon dioxide 

 and oxygen is assured; it is then allowed to flow into the potassium hy- 

 droxide and repeatedly drawn back and forth by means of the leveling 

 bulb E until the air in all of the capillary tubes is replaced by nitrogen, 

 the air being intermittently sent into the potassium pyrogallate to absorb 

 the slight traces of oxygen picked up in its passage through the capillary 

 tubing. The level of the potassium hydroxide in the capillary tube is 

 then brought to a definite point by lowering the mercury in the pipette 

 B, the final adjustment being made by the screw-cock N; a decreased ten- 

 sion is thus produced which raises the reagent to the desired mark. When 

 this point is reached the stop-cock b is turned 180 degrees to communi- 

 cate with the chamber D. We now have pure nitrogen in the capillary 

 tube leading from the potassium hydroxide reservoir to the stop-cock b. 

 Since all the other capillaries are likewise filled with pure nitrogen, pressure 

 is applied at screw-cock N to bring the potassium-pyrogallate solution to 

 a definite mark on the capillary tube before shutting off the stop-cock b. 

 After turning stop-cock a 180 degrees, the excess of nitrogen is then ex- 

 pelled through the stop-cock d by means of the leveling bulb E. 



Between the stop-cock d and the pipe coming from the outside of the 

 laboratory is a three-way stop-cock, one side of which is opened to the 

 room air. When taking the sample of air for analysis, this three-way 

 stop-cock is so turned as to allow direct communication between the gas- 

 analysis apparatus and the sampling pipe through which a suction pump 

 draws a current of outside air. Under these conditions, by lowering 

 the mercury reservoir E, mercury runs out of the pipette B and air is 

 drawn in through the capillary stop-cock d. The leveling bulb is again 

 raised and the pipette repeatedly swept out by pure air. When a 

 thorough and accurate sweeping out of the nitrogen is insured and the 

 pipette is full of uncontaminated outdoor air, the sample is ready to be 

 measured. The mercury is finally lowered to a mark somewhat below 

 the zero mark on the pipette. The suction pump is then stopped and the 

 three-way stop-cock between the gas-analysis apparatus and the sample 

 pipe (not shown in either figure) turned so as to communicate directly 

 with the room air. By raising the level of the mercury to the zero mark 

 on the bottom of the pipette B, a slight amount of air is expelled and the 



