i6 McDoUGALL AND HOWLES, Nitric Acid from Air. 



Several attempts were made to substitute some other 

 material in place of platinum-iridium for the electrodes, 

 but no very great success was achieved. In one case rods 

 of calcium oxide 6 mm. in diameter were prepared, and 

 it was possible to get the high-tension current to pass 

 through these on warming. The appearance of the 

 electric flame was, however, altered, being much thinner 

 and straighter than when platinum-iridium was used. It 

 was also very unsteady, with a tendency to constantly 

 creep back from the point of the electrode to the metal 

 connection. 



In continuing these experiments it was thought 

 desirable to observe the behaviour of the electric flame 

 when produced directly, by means of a high-tension 

 alternator, and, also to try under what conditions the 

 flame could be maintained and worked in parallel. 

 Messrs. Johnson and Phillips were kind enough to grant 

 permission for the experiments to be carried out in their 

 testing-house. 



An alternator, frequency 50, capable of generating 

 7,500 volts, was placed at our disposal, and the general 

 arrangement of the apparatus is shown by Fig. 6. 



A number of electrodes arranged in parallel circuit 

 were supported in a framework of wood, each electrode 

 being capable of adjustment. The voltage at the termi- 

 nals of the alternator was registered b\- means of an 

 electrostatic voltmeter. A similar instrument gave the 

 voltage at the electrodes when the discharge was passing. 

 An ampere-meter inserted in the circuit also enabled the 

 current taken to be read. 



The experiments were begun with a tension of 3,000 

 volts. All attempts to establish a flame when no choking 

 was included in the circuit resulted in failure. The elec- 

 trodes were immediately fused, the current meanwhile 



