12 Composition of the Atmosphere 



Van Breda 1 in Delft made analyses of air by the nitric-oxide eudiom- 

 eter on 195 days in 1781 and 1782, but the results have little quantitative 

 value. 



In an address before the Academy in Barcelona on May 22, 1790, An- 

 tonio de Marti 2 announced the results of his experiments on the "Quan- 

 tity of vital air in the atmosphere, and the different methods of measuring 

 it." Among other means he used nitric oxide and reported uniformity in 

 composition of the air. 



During some days of the year 1787, in which the common air experienced no varia- 

 tion by means of nitrous air, since 100 parts of each were uniformly reduced to 99 or 00, 

 I was desirous of making a comparative trial of the same common air by means of iron 

 and sulphur, and I observed that of 100 parts of air there remained from 79 to 81 and 

 that consequently, from 19 to 21 hundredths had disappeared. 



One of the most extensive contributors to our knowledge of the com- 

 position of the air obtained by means of the nitric-oxide eudiometer was 

 Alexander von Humboldt, and in his records we find recognition of the 

 existence not of dephlogisticated air but of oxygen, accepting Lavoisier's 

 newest theory with regard to the air. von Humboldt recognized the im- 

 portance of testing the purity of the nitric oxide used, and determined 

 the degree to which it would dissolve in a ferrous-sulphate solution. 



In 1798 von Humboldt 3 had analyzed the air collected in a balloon 

 journey by Garnerin and Beauvais at an altitude of 1303 meters and com- 

 pared it with the air of Paris, using nitric oxide and ferrous sulphate. 

 The air in Paris showed 27.6 per cent oxygen and the balloon air 25.9 per 

 cent. These balloon samples are of general interest in that they sub- 

 stantiate the simultaneous observations of de Saussure, 4 who, using a 

 nitric-oxide eudiometer, analyzed air taken from the tops of several moun- 

 tains. Though the results are not expressed numerically, de Saussure 

 concludes that the air of mountains is somewhat less pure in vital air 

 than that of the neighboring plains and valleys. 



Although a large number of desultory investigations had been made by 

 Ingen-housz in London, van Breda in Delft, Pickel in Wurzburg, Lam- 

 padius in Freiburg, Lichtenberg in Gottingen, Scherer in Vienna, and 

 Breze, all of whom used the nitric-oxide eudiometer, yet von Humboldt 5 

 was dissatisfied with these researches, believing that analyses of the air 

 should be accompanied by observations with regard to its elasticity, tem- 

 perature, moisture, electricity, and clearness. He accordingly undertook 

 an extensive series of observations with regard to the oxygen content of 



1 Letter to J. Ingen-housz, Vermischte Schriften, 2d ed., Vienna, 1784, 2, p. 441. 



1 This lecture was translated into French and printed in the Journal de Physique, 

 1801, 52, p. 173. Abstracted in Gilbert's Annalen der Physik, 1805, 19, p. 389. The 

 lecture was also printed in English in the Philosophical Magazine, 1801, 9, p. 250. 



3 von Humboldt, Journal de Physique, 1798, 47, p. 202. 



4 de Saussure, Voyages dans les Alpes, Neuchatel, 1803, 1 , p. 427. 



5 von Humboldt, Versuche liber die chemische Zerlegung des Luftkreises, Braun- 

 schweig, 1799, p. 150. 



