30 Composition of the Atmosphere 



Unfortunately nowhere in Bunsen's subsequent publications do we 

 find any record of the analyses of this large number of samples of air, 

 and obviously the pressure of other work prevented his carrying out 

 this inquiry. It is greatly to be regretted that with his masterful tech- 

 nique such analyses could not have been made. 



Although Lavoisier had shown that when phosphorus was burned in 

 air there was an increase in weight corresponding to the diminution in 

 volume of the air, nevertheless no air-analyses were based upon gravi- 

 metric determinations until the appearance in 1833 and 1834 of the unique 

 method of Brunner 1 in Berne. Brunner devised a plan of passing a 

 volume of air through a tube that contained some suitable absorbent for 

 oxygen which could be weighed. All previous determinations had been 

 made over water, or occasionally mercury, upon relatively small volumes 

 of air confined in glass tubes, eudiometers, etc., but with Brunner's 

 method, a considerably larger volume of air could be used. Furthermore, 

 it was possible by this process to measure likewise the amount of nitrogen 

 remaining in the gas, and thus make a determination not only of oxygen 

 by weight, but of nitrogen by volume. After a number of preliminary 

 experiments made with iron and with copper, Brunner finally decided 

 upon phosphorus as the best absorbent. With perfectly dry phos- 

 phorus and a very moderate air-current, he found that oxygen was 

 rapidly and quantitatively absorbed. 



In 1833 Brunner made a series of experiments in Berne in which he 

 determined the average oxygen content of the air as 21.0705 per cent. 

 The agreement was usually within 0.1 per cent, although occasionally the 

 variation was as high as 0.2 per cent. Of interest, also, is the fact that he 

 analyzed air taken on the Faulhorn on July 18, 19, and 20 of the same 

 year; from 14 determinations he found the oxygen varying from 20.75 to 

 21.11 per cent, the average of all being 20.915. Eight years later, in 

 July 1841, 2 Brunner made 7 experiments in the same manner as those 

 made at Berne, and found ranges from 20.75 to 20.867 per cent, with an 

 average of 20.821 per cent. The fact that this latter value is very much 

 less than those found 8 years before is explained by Brunner on the ground 

 that there was probably an error in the measurement of the size of the 

 vessel used in the earlier experiments. Brunner's article is particularly 

 valuable, as it contains a critical discussion of methods and of the limit 

 of accuracy of the various methods that had been proposed for absorbing 

 oxygen. 



While Brunner had successfully weighed the oxygen absorbed from the 

 air, he had always measured the volume of nitrogen. In 1841 Dumas and 

 Boussingault 3 published a research which in plan was quite similar to 

 that of Brunner, except that they not only weighed the oxygen but like- 



1 Brunner, Poggendorff's Annalen der Physik und Chemie, 1833, ser. 2, 27, p. 1 ; 

 also, ibid., 1834, ser. 2, 31, p. 1. 



1 Brunner, Annales de Chimie et de Physique, ser. 3, 1841, 3, p. 305. 



3 Dumas and Boussingault, Annales de Chimie et de Physique, ser. 3, 1841, 3, p. 257. 



