FLAMES OF ATOMIC HYDROGEN 141 



tungsten rods 3.2 mm. in diameter which made an angle of 55 degrees with 

 one another. The rate of flow of hydrogen which hathed the electrodes was 

 14.2 liters per minute (30 cubic feet per hour). From the temperature 

 rise of the copper block the heat delivered to the surface was found to 

 correspond to 3100 watts when the electrode tips were 3 to 5 mm. from 

 the copper surface. This decreased to 2800 watts at 13 mm., 2500 at 25 mm., 

 and 2200 at 35 mm. With the arc turned off but the molecular hydrogen 

 burning in the air, the rate of heating corresponded to 250 watts with the 

 electrodes 6 mm. from the surface. Subtracting this energy delivered by 

 the combustion of the hydrogen in the air, we find that the energy carried 

 to the metal by the atomic hydrogen ranged from 2850 to 1950 watts. 

 Thus with the electrodes 3 mm. from the metal 82 per cent of the power 

 input into the arc was delivered to the copper surface. This efficiency 

 became 78 per cent at 6 mm., 71 at 13 mm., 65 at 25 mm., and 55 per cent 

 at 35 mm. The energy corresponding to the complete combustion of 14.2 

 liters of hydrogen per minute is 2360 watts. Actually, only 250 watts or 

 1 1 per cent of this reaches the copper. The total energy of the arc and the 

 flame of molecular hydrogen is 5870 watts, of which 3100 watts or 53 

 per cent is delivered to the copper. 



An oxy-acetylene flame from a standard welding torch consuming 30.6 

 liters of oxygen per minute (64.8 cubic feet per hour) and 28.6 liters of 

 acetylene per minute (60.6 cubic feet per hour) delivered energy at the 

 rate of 4400 watts to the copper surface. A smaller torch consuming 13.7 

 liters of oxygen per minute and 13.0 of acetylene (29.0 and 27.5 cubic 

 feet per hour, respectively) gave energy to the copper at the rate of 3900 

 watts. If we take the heat of combustion of the acetylene to be 302,000 

 calories corresponding to complete oxidation according to reaction I, the 

 efficiency of the heat delivery by these flames is 17.6 per cent with the larger 

 torch and 34.2 with the smaller. The energy deUv&red is, however, 52 and 

 loi per cent, respectively, of the heat energy generated if the combustion 

 proceeded only as far as indicated by reaction III. 



The data in Table II and the foregoing results show that the intense 

 heat of the atomic hydrogen flame extends a considerable distance beyond 

 the arc between the electrodes. Some measurements were also made of the 

 length of time required to melt the end of rods 6.3 mm. in diameter 

 (J4 inch) of Armco iron which were held in the flame at different distances 

 from the electrode tips, the axis of the rods being perpendicular to the 

 direction of motion of the flame gases. The rods were at room temperature 

 when introduced into the flame. Table III gives the time in seconds before 

 fusion at the end of the rod occurred. 



Every refractory material which has been tried, except carbon, can 

 be melted with comparative ease by the atomic hydrogen flame. Many sub- 



