p. C. WILHELMSEN, R. LUMRY AND H. EYRING 79 



the system with oxygen free hydrogen, the hght from the luminol 

 was extinguished. It required less than a minute of bubbHng hydrogen 

 through the system before the hght from the luminol faded below the 

 visible threshold. The luminous bacteria continued to glow for a cou- 

 ple of minutes after the luminol ceased luminescing. This indicates 

 that a higher concentration of oxygen is required by the luminol to 

 produce a visible light than is required by luminous bacteria. 



If the ferricyanide solution is now added to the luminol solution by 

 tilting the A tube, the bright chemiluminescence characteristic of the 

 reaction luminol and ferricyanide when saturated with air is produced. 

 An hour of bubbling hydrogen through the solutions did not visibly 

 affect the intensity of the light produced by luminol and ferricyanide. 

 This means that a smaller quantity of oxygen is required in this case 

 than is used with luminous bacteria — a very small quantity indeed 

 considering that a partial pressure of 0.0007 mm Hg of O2 is all that 

 is required by bacteria ( Harvey and Morrison, 1923 ) . However, when 

 the hydrogen was bubbled through the system for twenty-four hours, 

 the light produced by the addition of ferricyanide to luminol became 

 faint and of short duration. Bremer (1953) performed a similar group 

 of experiments where the oxygen was removed by repeated freezing 

 of the solution and evacuation of the space above. She has reported 

 results similar to those just described. 



The small residual amount of light produced with luminol and 

 ferricyanide in the supposed absence of oxygen is possibly due to a 

 small trace of oxygen still remaining. However, Bremer (1953) was 

 not able to extinguish the residual glow by extended treatment with 

 repeated freezing and evacuation of the system, and the present 

 authors found no difference in the light obtained when the hydrogen 

 was passed through the system for one day or for five days. The 

 hydrogen employed in these experiments was purified by passing over 

 platinized asbestos and might conceivably have contained a small 

 trace of oxygen. The existence of a second, less efficient mode of 

 chemiluminescence is the alternative. Another line of evidence that 

 makes it troublesome to exclude the existence of this less efficient 

 reaction comes from another source. 



It has been found that hydrazine and ferricyanide give out a feeble 



