66 Composition of the Atmosphere 



SUMMARY OF HISTORICAL DIGEST. 1 



While the earliest studies of the composition of the atmosphere can 

 hardly be considered as giving results of quantitative significance, these 

 researches stimulated greatly the study of chemistry in general and air- 

 analysis in particular, the great interest in the composition of the atmos- 

 phere leading to the rapid development of many methods of analyses. 



Seldom has a philosophical instrument or a chemical process attracted 

 so much attention as did the eudiometer, which utilized the reaction be- 

 tween nitric oxide and air. Although soon discarded for methods better 

 founded scientifically, the apparatus nevertheless was a ready and port- 

 able means for increasing the interest of investigators and diffusing a 

 knowledge of the composition of the air. The successors of this method, 

 2. e., methods involving the use of absorbents like alkaline sulphides or 

 phosphorus, or employing explosion with hydrogen, all of which depended 

 upon volumetric measurements, soon demonstrated the difficulties in air- 

 analysis difficulties which taxed the ingenuity and the patience of prac- 

 tically all the prominent chemists. 



One figure in this early history of air-analysis shines out above all 

 others that of the scholarly, isolated Scheele. That Scheele may rightly 

 be designated as the pioneer in the study of the chemistry of the air few 

 who examine the literature can deny. His results, while admittedly of no 

 quantitative significance, do nevertheless imply a knowledge of the chem- 

 istry of the air, of its composition, and of the possibilities of change in its 

 composition, which was expressed no more clearly by other writers many 

 years later. 



Eudiometric observations were exclusively relied upon during the first 

 50 years of the development of air-analysis, but later gravimetric methods 

 were introduced by Brunner and Dumas in which the oxygen was ab- 

 sorbed by copper or phosphorus, and was subsequently weighed. Then 

 there followed a return to the hydrogen-explosion method, which was ad- 

 vanced to the highest degree of accuracy by Bunsen, Regnault, Frankland 

 and Ward, and Morley. Meanwhile the interesting method of Liebig, 

 employing an alkaline solution of pyrogallic acid, and the copper eudio- 

 meter of von Jolly made their appearance. 



In all of these earlier researches we find that while the chemical proc- 

 esses involving the absorption of oxygen from the atmosphere were capa- 

 ble of innumerable refinements, the grossest errors were due to purely 



1 In compiling the historical material in this book I have been greatly aided by Miss 

 B. Clark, librarian of the William Ripley Nichols Library of the Massachusetts Institute 

 of Technology; and Mrs. Austin Holden, of the Library of the American Academy of 

 Arts and Sciences; and my thanks are especially due to Dr. J. S. Billings and his associate, 

 Dr. Henryk Arctowski, of the New York Public Library. The facilities of the library of 

 the Harvard Medical School, the Library of Congress, and the Surgeon General's Library 

 have also been freely drawn upon. 



I am also much indebted to Dr. E. P. Cathcart, of Glasgow, 1911-1912 Research 

 Associate of the Carnegie Institution of Washington, attached to this laboratory, for hia 

 painstaking and critical reading of the entire manuscript of this book. 



