130 



Mr. W. L. Upson : Observations 



C-Cu. The arc was very steady ; of a purple colour, 

 except at the point of junction with the copper, where 

 there was a small region of green colour. A small 

 deposit of carbon quickly formed on the copper. If this 

 were not continually removed, the arc soon assumed the 

 characteristics of carbon-carbon. The deposit on the 

 apparatus was very slight. The carbon terminal burned 

 away quite rapidly, assuming a three-stage form, as 

 shown in fig. 3. 



Fisr. 3. 



4S ^jCi'aT&T. 



Bull Tied 



Blacfa 



C-Fe. This arc continually splutters and hisses, and is 

 very hard to measure. It is very bright ; more blue 

 (from iron) than purple (from carbon). When the iron 

 has reached a certain temperature, bubbles form- 

 probably magnetite — and the energy consumption in- 

 creases. The arc, however, now becomes steady. It was 

 drawn out to 0*5 in. with 5 amperes and 80 volts 

 across the arc. 



C-Al. This arc started more readily than when its poles 

 were reversed. There appears not to be any very heavy 

 formation of aluminium oxide acting as an insulator on 

 the end of the Al electrode. But once started, the arc 

 was not very stable, and would not be drawn out to more 

 than 0*3 in. with a current of from 10 to 12 amperes. 

 The Al electrode was deeply pitted and very hard, con- 

 taining a deposit of carbon embedded in it. The 

 apparatus was coated with a light grey deposit of Al, but 

 not so thickly as in the case of the Al-C arc in hydrogen. 

 The end of the carbon was rounded, and showed in- 

 dications of a crater form. A pungent odour was 

 emitted as in the case of the same electrodes with current 

 reversed. 



