History of Air-Analysis 57 



February are given in table 41 as illustrative of the accuracy of his work 

 and of the magnitude of the fluctuations experienced by him. 



An examination of all of his results shows a minimum of 20.877 per 

 cent, a maximum of 20.971 per cent, with a difference of 0.094 per cent, 

 and an average of 20.93 per cent of oxygen. Hempel points out that his 

 results compare favorably with those of Kreusler, who found 20.911 per 

 cent, and of Morley, who obtained 20.949 per cent, each investigator 

 using a wholly different method. 



Obviously to three such skilled experimenters as Morley, Kreusler, 

 and Hempel, the uncertainty regarding the general question as to the 

 constancy, or lack of constancy, of the oxygen content of the air was 

 somewhat disconcerting, and it is not surprising that we find them in 1886 

 engaging in a cooperative investigation. Morley in Cleveland, Kreusler 

 in Bonn-Poppelsdorf, and Hempel in Dresden collected samples at the 

 same time, making due allowances for geographical location. In addition, 

 Hempel secured the aid of Pusinelli, who took samples in Para, Brazil, 

 and of Schneider, who simultaneously took samples at Tromso in Norway. 

 Thus the times for collecting; were: 



*& 



Dresden 2 h 38 m p.m. 



Tromso 3 00 p.m. 



Cleveland 8 h 18 m a.m. 



Para 10 31 a.m. 



Bonn 2 12 p.m. 



Kreusler, 1 who made the determinations with his glowing copper-wire 

 eudiometer, published his results independently shortly before Hempel's 

 paper 2 appeared. 



Kreusler abates somewhat his criticism of the pyrogallic-acid method, 

 but still adheres to von Jolly's copper eudiometer. His results need not 

 here be reproduced in full, as they are in part incorporated with those of 

 Hempel and Morley in table 42. Kreusler found percentages of oxygen 

 ranging from 20.907 to 20.939, substantiating his earlier findings and be- 

 lief that the oxygen fluctuations, in spite of changes in meteorological 

 conditions, are small. The average is 20.922 per cent, which is a little 

 higher than the average of his earlier results, i. e., 20.911. Hempel's 

 summary of the complete investigation includes the results of both Kreus- 

 ler and Morley. A specimen set of records from April 1 to April 11, 1886, 

 will serve to show both the agreement of duplicates and the variations 

 experienced in various places. The samples from Tromso, Dresden, and 

 Para were all analyzed alike, in that both oxygen and carbon dioxide were 

 simultaneously absorbed. Oxygen alone was determined in the samples 

 collected in Bonn and Cleveland. 



The Tromso analyses usually showed an agreement within 0.01 per 

 cent on the same day; on several occasions the difference was 0.03 per 

 cent, but the average for each day showed a fluctuation ranging from 21 

 per cent down to 20.90 per cent. It should be borne in mind that the 



1 Kreusler, Berichte der deutschen chemischen Gesellschaft, 1887, 20, p. 991. 



2 Hempel, ibid., p. 1864. 



