204 Holborn and Day — Gas Thermometer at 



Originally the two elements had agreed for all positions to 

 within 5 microvolts. 



Further examples could be cited, but we will confine our- 

 selves to two where efforts were made to restore the damaged 

 elements. 



The element C, cut from the same wire as T a was in use for 

 a long time for high temperatures in a long oven and there 

 exposed to these gases, after which the following differences 

 were obtained by comparison with the normal elements Gr and 

 H under unchanged condition's of temperature distribution. 



t 



H-C 



G-C 



200° 



+ 5MV 



+5MV 



' 300 



+ 5 



+6 



400 



+ 4 



+5 



500 



— 11 



+6 



600 



— 13 



+7 



700 



— 14 



+ ' 



800 



— 13 



+5 



900 



— 12 



+7 



1000 



— 13 



+7 



1100 



— 10 



+8 



1200 



— 9 



+8 



When this same element C was introduced into the short 

 oven containing melted copper however, where the conditions 

 of temperature distribution were very different, it gave 10,092 

 MV as the melting temperature while the two normal elements 

 showed 10,212 microvolts. 



C was then taken out, glowed electrically at full white heat 

 for several hours and again introduced into the copper cruci- 

 ble (with proper porcelain protection of course), when it gave 

 10,170 under the same conditions as before. 



The same measurement was then a third time repeated after 

 5 cm had been cut from both wires at the hot junction — the 

 electromotive force now proved to be 10,220 microvolts. In 

 this condition further measurements were made of the melting 

 points of lead, cadmium and zinc with results 2513, 2460 and 

 3371 microvolts respectively, all in good agreement with the 

 normal values. 



As has been said the glowing was done electrically, as much 

 as 17 amperes being sent through the wires. Connected in 

 series both wires glow with equal intensity at high tempera- 

 tures, the smaller resistance of the platinum when cold being 

 offset by its larger temperature coefficient. 



An element B of the same group was used several times in 

 an oven tube of a new material which was being tried for the 

 first time, up to a temperature of 1600°. 



