504 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



nitrogen is wanted in the form of nitric acid, and where power is 

 available the simplicity of the arc furnaces makes the rapid installa- 

 tion of a large battery of them relatively easy. The cumbersome 

 and expensive part of the arc installation has always been the large 

 stone towers for absorbing in water the gases after leaving the 

 furnaces. On this part of the process, however, there seems excellent 

 opportunity for radical improvement, and during the past year this 

 laboratory has made decided progress in this direction, especially on 

 the use of solid adsorbents for the preliminary concentration of the 

 active gases. The sam& procedure is also applicable in the manufac- 

 ture of nitric acid by the oxidation of ammonia. This line of investi- 

 gation is being actively continued and the results thus far obtained 

 are being prepared for publication. 



ELECTRIC DISCHARGE IN GASES. 



While there at present seems little hope of greatly reducing the 

 consumption of electric power in the arc process proper, the study 

 of electric discharge in nitrogen both by itself and mixed with other 

 gases under a wide range of pressure and other conditions presents 

 an extremely promising field for investigation which the laboratory 

 is energetically developing. Aside from the possibility that out of 

 such investigations may eventually come knowledge enabling us to 

 more efficiently apply the electric current to the direct fixation of 

 nitrogen, even greater importance is attached to this work because 

 of the light it may throw upon the ultimate structure and chemical 

 properties of the atoms and molecules here involved. In the present 

 state of development of the art it would seem primarily through 

 such knowledge as this that further fundamental improvements in 

 any of the processes of nitrogen fixation can most confidently be 

 looked for. This forms an extension of the work on ozone and active 

 nitrogen mentioned in last year's report. Particularly significant is 

 the progress made this past year in regard to the properties and be- 

 havior of active nitrogen which is formed when powerful electric 

 discharges are passed through pure nitrogen at low pressure. Under 

 these conditions the nitrogen after leaving the path of the discharge 

 continues to glow for an appreciable time and reacts readily with 

 many substances toward which ordinary nitrogen is quite inert. 



In the arc process as commercially practiced, electrical, thermal, 

 and photochemical phenomena are so closely intertwined as to be 

 indistinguishable. The electrical investigations of the laboratory 

 just referred to aim, among other things, at isolating and studying 

 the electrical and photochemical parts of these phenomena. 



THERMAL PROCESSES. 



On the other hand, the study of the purely thermal aspect of the 

 phenomena occurring in the arc is also of great importance. This 

 has found its practical expression, for instance, in the Haiiser 

 process, by which a certain amount of nitric acid was made by the 

 Germans during the war. In this process the heat of explosion 

 of a mixture of air and coal gas replaces that of the electric arc. 

 If working under this principle it should prove possible to combine 

 even a moderate recovery of both power and the oxides of nitrogen, 

 it is easy to imagine important developments ultimately in this 

 direction. The laboratory has as yet devoted very little detailed 



