28 



Composition of the Atmosphere 



The results for the first month, which are fairly representative of the 

 remainder of the study, are given in table 5. 



The use of a metal to absorb oxygen was first suggested by Scheele, 1 

 who employed metallic iron. A Spaniard, Luzuriaga, 2 in 1784, used lead, 

 but his results are not available. 



The first practical use of a metal as an oxygen absorbent in air-analysis 

 was made by Theod. de Saussure, 3 who employed lead shavings moistened 

 with a very little water. After shaking them 3 hours, he found that the 

 absorption was complete, de Saussure criticized the earlier methods, 

 since so many divergent results were obtained by different workers, con- 

 sidering the Volta eudiometer especially open to criticism, as there was 

 always danger of an impurity in the hydrogen. He believed the lead 

 method, though not so convenient, to be much more accurate. A state- 

 ment of his results is given in table 6. 



Table 6. Results obtained by de Saussure with the lead method. 



1 Meadow 1 league from Geneva. 



From these results one concludes that de Saussure determined carbon 

 dioxide and oxygen together and subsequently deducted the carbon diox- 

 ide. His results show surprising constancy in the oxygen content of the air. 



Dupasquier, 4 employing the alkaline ferrous hydroxide originally em- 

 ployed by Scheele, found that normal air always gave 21 per cent. Some- 

 what later, Brunner 5 reverted to the precipitated ferrous hydroxide 

 method, but reported no air-analyses. 



1 Scheele, Air and Fire, London, 1780, p. 13. 



2 See Kopp's Geschichte der Chemie, 1845, 3, p. 211. 



3 de Saussure, Annalen der Physik, 1836, ser. 2, 8, p. 171. 



4 Dupasquier, Annales de Chimie et de Physique, 1843, 3d ser., 9, p. 247. 



6 Brunner, Poggendorffs Annalen der Physik und Chemie, 1848, Erganzungsband , 

 2, p. 509. 



