RESEARCHES UPON THE CHEMICAL PROPERTIES OF GASES. 209 



presence of sodium acetate for the quantitative determination (by absorption) of 

 oxygen in a gas mixture. According to this author, the change from colorless to 

 greenish blue renders the solution a suitable reagent for the recognition of oxygen. 

 Very minute quantities of oxygen can be detected. The preparation of the reagent 

 (reduction from chromic chloride by zinc in presence of hydrochloric acid) is 

 effected in a Woulfe bottle, through which the gas is already passing, and the air 

 thus removed previous to the test. 



Fuming sulphuric acid is said to dissolve oxygen (B. Lean, J. Cli. Soc, 1892, 

 p. 880). 



IS^othing need be said here concerning the detection of oxygen when occurring 

 in large quantities in a gas mixture. 



The general study of gas reactions has not yet attracted the attention it de- 

 serves. The majority of articles bearing upon the subject have referred only inci- 

 dentally to reactions by which a particular gas, or group of gases, may be recog- 

 nized. 



Every effort has been made to cite references to all published statements con- 

 cerning reactions which I have detailed. It is probable, however, that many have 

 been overlooked. 



In conclusion, I have to express my thanks to Messrs. R. B. Carnahan, Gustav 

 Miller and Henry Phillips, for assistance in the work, and especially to Mr. Henry 

 T. Weed. 



