HYDROGEN INTO ATOMS 197 



at 2300°, an amount probably sufficient to account for the anomalies 

 found by Siegel. 



Thus, the explosion method gives additional evidence for the dissocia- 

 tion of hydrogen and confirms the substantial accuracy of the results. 



RATE OF FORMATION OF ACTIVE HYDROGEN 



It has been shown -- that the disappearance of hydrogen in contact 

 with a heated filament is caused by the deposition of atomic hydrogen on 

 the bulb. 



The present theory enables us to calculate the rate at which atomic 

 hydrogen should be formed in contact with a tungsten wire. The rate at 

 which atomic hydrogen is deposited on the bulb should naturally be less 

 than that at which it is formed by the wire. 



In the paper referred to, it was stated that the disappearance of hy- 

 drogen "was often quite marked when the wire was at a temperature as 

 low as 1300° K.," but very few quantitative data at such low temperatures 

 were given. By looking through the original notes of these experiments, 

 I find that at low temperatures the highest rates of disappearance were as 

 follows : 



Experiment 160. Filament temperature 1200° K. In seven minutes 

 the pressure fell from 16.4 to 15.6 microns, although at 1100° K. no 

 decrease in pressure could be observed. The surface of the filament was 

 0.15 sq. cm. The rate of disappearance was 1.4 cubic millimeters of H2 

 per minute per sq. cm. of surface. 



Experiment 173. With the filament at 1270° the pressure decreased 

 from 16.2 to 15.0 microns in three minutes. The surface of the filament 

 was the same as before. This corresponds to a rate of 3.7 cubic mm. 

 per minute per sq. cm. 



In each case the hydrogen continued to disappear at a gradually de- 

 creasing rate for a half-hour or more. Because of this fatigue effect we 

 shall here consider only the initial rates. 



Let us now calculate the rate at which atomic hydrogen should have 

 been produced by wires at these temperatures. In Equation 26 we may 

 place pi = o; p2 = P and may neglect the second term of the denominator 

 at these low pressures and temperatures. Since the factor \/2kR is equal 

 to 17.15 and tti is unity, we thus obtain 



K = 32S. VT7f7o)VP. (76) 



In this equation 00 is the rate of dissociation of hydrogen in grams per 

 second per sq. cm. of filament surface. Let R be the rate of dissociation 

 ^'^ Jour. Amer. Chem. Soc, 34, 1310 (1912). 



