FLAMES OF ATOMIC HYDROGEN 121 



to move transversely so that it became tan shaped. Iron rods 2 or 3 mm. 

 in diameter melted within one or two seconds when they were held 3 to 

 5 cm. above the arc. 



By directing a jet of hydrogen from a small tube into the arc, the atomic 

 hydrogen could be blown out of the arc and formed an intensely hot flame. 

 To maintain the arc in a stable condition the electrodes were brought closer 

 together (i to 3 mm.) but the arc did not remain entirely between the 

 electrodes, but extended as a fan to a distance of 5 to 8 mm. The flame of 

 atomic hydrogen, however, extended far beyond the arc. At distances of i 

 or 2 cm. from the arc molybdenum (melting point 2900 deg. K.) melted 

 with ease. Near the edge of the arc tungsten rods (m. p. 3660 deg. K.) 

 could be melted. Quartz melted with much more difficulty than molyb- 

 denum, indicating that the extreme rapidity of heating of the metals was 

 partly due to their catalytic action in causing the atoms to combine on their 

 surface. 



The use of hydrogen under these conditions for melting metals has 

 proved to have many advantages. Iron can be melted without contamination 

 by carbon, oxygen or nitrogen. Because of the powerful reducing action 

 of the atomic hydrogen, alloys containing chromium, aluminum, silicon or 

 manganese can be melted without fluxes and without surface oxidation. 

 With these flames of atomic hydrogen even fairly large pieces of aluminum 

 oxide, AI2O3, magnesium oxide, MgO, or thorium oxide, Th02 can be 

 melted with ease. The oxides thus heated show no apparent reduction tu 

 metal, perhaps because any metal that is formed is volatilized at these higii 

 temperatures. 



The technical development of methods for utilizing flames of atomic 

 hydrogen has been the work of several men, among whom Robert Palmer 

 and R. A. Weinman should be particularly mentioned. 



An article by Mr. Weinman and the writer describes the application of 

 these flames to the welding of metals. 



THE TEMPERATURE OF THE ATOMIC HYDROGEN FLAME AS 

 COMPARED TO OTHER FLAMES 



Let us suppose we could obtain atomic hydrogen in bulk at atmospheric 

 pressure and room temperature and that we could then let this "burn" to 

 the molecular form in a flame. What would be the temperature of this 

 flame and how would it compare with that of other flames? Taking the 

 heat of reaction (for 2 grams) to be 98,000 calories and taking the specific 

 heat of molecular hydrogen (for 2 grams) to be 6.5-1-0.00097, we find 

 that the heat of the reaction would be sufficient to heat the hydrogen to 

 9200 deg. K. 



