D. A. Kreider — Oxygen in Air and Aqueous Solution. 361 



Aet. LIU. — The Determination of Oxygen in Air and in 

 Aqueous Solution ; bj D. Albert Kheider. 



[Contributions from the Kent Chemical Laboratory of Yale University, LX.] 



While there is little to be hoped for by way of improve- 

 ment in the accuracy of present known methods for the deter- 

 mination of oxygen in the air, some choice as to manipulation 

 may nevertheless be desirable, and a process which is not lim- 

 ited wholly to the methods and apparatus of ordinary gas 

 analysis will doubtless often be found serviceable. 



The very satisfactory results which I have obtained in the 

 determination of perchlorates by the action of the liberated 

 oxygen upon hydriodic acid through the medium of nitric 

 oxide^ has led me to test this action upon the oxygen of the 

 air, where only the smaller amount of oxygen and its greater 

 dilution with nitrogen might be expected to be unfavorable. 

 However with the apparatus and manipulation herein described 

 it will be seen that the method affords a means for the deter- 

 mination of the oxygen of the air or of dissolved oxygen with 

 ease and rapidity and with sufficient accuracy for all practical 

 purposes. 



The method in brief is simply the conducting of a known 

 volume of air through a strong solution of hydriodic acid in 

 the presence of nitric oxide; subsequently neutralizing the 

 acid with potassium bicarbonate and titrating the liberated 

 iodine with standard decinormal arsenic solution from which 

 the equivalent volume of oxygen is readily calculated. By 

 several simple devices, to be described, all calculations may be 

 done away with and the percentage of oxygen seen imme- 

 diately by the volume of arsenic solution required for the titra- 

 tion. 



The volume of oxygen found by means of the arsenic solu- 

 tion is, of course, under the standard conditions of tempera- 

 ture and pressure (0° and 760""°"), and it is therefore essential 

 either to calculate this volume into that which it would occupy 

 under the conditions of the experiment, or to reduce to the 

 standard conditions of temperature and pressure the volume 

 of air taken. The latter plan is the more satisfactory since by 

 Lunge's ingenious devicef the reduction can be readily 

 effected without any calculation and independently of chang- 

 ing temperature and pressure. For my purpose the following 

 arrangement of two burettes answered admirably. One 

 burette graduated to 120°™' contained over mercury the same 



* This Journal, 1, 287. \ Zeitschr. fur Ang. Chem. 1890, 139. 



