History of Air-Analysis 



55 



plosion for the determination of oxygen. A sufficiently large sample was 

 taken to eliminate the errors incidental to working with minute quantities 

 of gas such as would be obtained from blood; the results given in table 38 

 were obtained for the percentage of oxygen. The extremely low value 

 of 20.68 is attributed by the author to a defect in the particular eudiometer 

 used for this single determination. The author points out that if one 

 wishes to make exact gas-analyses it is desirable to test the eudiometer 

 previously with normal air. 



Table 38. Percentages of oxygen determined on atmospheric air by Geppert. 



Contemporaneously with Morley and von Jolly, but working entirely 

 independently, Hempel, employing potassium pyrogallate as the absorb- 

 ing agent, began a research on the composition of the air. 1 In 1877 he 

 found, as the result of many analyses, differences so great as to be ex- 

 plainable only on the ground of imperfect technique. Subsequent de- 

 velopment of apparatus and method yielded a procedure so accurate that 

 duplicate analyses of each day's sample did not vary from one another 

 by more than 0.02 per cent. On five different days in the fall of 1877 he 

 found 20.89, 20.76,20.96, 20.91, and 20.90 per cent of oxygen, respectively. 

 In 1879, analyses were made in April and May as follows: 



p. ct. 



Apr. 24 21.16 



Apr. 25 20.91 



Apr. 26 20.92 



Apr. 27 20.83 



Apr. 28 20.87 



Apr. 29 20.70 



p. ct. 



Apr. 30 20.83 



May 1 20.82 



May 3 20.55 



By means of the improved apparatus, an interesting comparative 

 series of analyses was made, samples of air being collected in July 1883, 

 simultaneously by Professor Hempel in Dresden and Professor E. Hagen 

 on the steamer between Liverpool and New York, all samples being taken 

 at 8 a. m. The results are given in table 39. 



Table 39. Determinations of oxygen in atmospheric air, collected at sea and in Dresden. 



Hempel, Berichte der deutschen chemischen Gesellschaft, 1885, 18, p. 267. 



