82 Composition of the Atmosphere 



PLAN AND METHODS OF RESEARCH. 



The report of the research carried out with this apparatus may be sub- 

 divided into several parts as follows: 



(1) The main study of the comparative oxygen-content of uncontami- 

 nated outdoor air under all conditions as to wind direction and strength, 

 temperature, cloud formation, barometer, and weather, including rain, 

 snow, fog, and mist. 



(2) A study of the influence of the temperature of the reagent upon 

 its absorptive power. 



(3) An examination of samples of air collected on the North Atlantic 

 Ocean between Montreal and Liverpool, and between Genoa and Boston. 



(4) Analyses of air obtained from the top of Pike's Peak. 



(5) Analyses of air taken in the crowded streets of Boston. 



(6) Analyses of air taken in the Boston and New York subways. 



(7) An experimental research with various absorbents for oxygen. 

 Before proceeding to a description of the routine of air-analysis with 



this apparatus, a discussion of the method of procuring samples of un- 

 contaminated outdoor air is advisable. By far the greater number of 

 analyses were made of air collected near the laboratory, and a permanent 

 installation was made to secure convenient and accurate sampling of air. 

 It is unnecessary at this point to describe the methods of sampling em- 

 ployed when samples were taken at some distance from the laboratory. 



METHOD OF COLLECTING OUTDOOR AIR. 



As the laboratory is located near a large power-house, it was feared 

 that in spite of all precautions there would be a contamination of the at- 

 mosphere due to the products of combustion from the large furnaces. On 

 the other hand, as the prevailing winds are from the southwest and the 

 power-house is north of the laboratory, it seemed probable that during 

 the prevailing winds the contamination should not be perceptible. In 

 order to provide for a possible variation in composition on two sides of 

 the building, arrangements were made for taking samples on both the 

 east and west sides. The sampling arrangements are as follows: 



A standard ^s-inch brass pipe (7 mm. internal and 10 mm. external 

 diameter) was extended out from the west wall of the laboratory, 4.8 

 meters from the ground and at a distance of 2.2 meters from the wall. 

 The end was pointed downward so as to prevent clogging by water, ice, 

 or dirt. This pipe was then brought into the laboratory, conducted to 

 the sink near the gas-analysis apparatus, and a water-suction pump so 

 connected as to suck continuously a current of air from outdoors through 

 the pipe. The intake tube of the gas-analysis apparatus was attached 

 to the air-pipe, so that it was possible to have a continuous stream of fresh 

 outdoor air passing by the analysis apparatus. Similarly, a second pipe 

 was carried out from the east side of the building at the same distance 

 from the ground as the pipe on the west side. This pipe was also con- 



