High Temperatures. 



193 



The attempt to saturate the melted silver by allowing 

 oxygen to bubble through it and thereby to reach a definite 

 point of solidification for this condition led to no satisfactory 

 result. The thermo-element showed considerable temperature 

 oscillations throughout the solidification, but the mean, as was 

 to be expected, lay much below the other determinations. 

 Four observations gave the temperatures 939°, 938°, 942° and 

 938° — approximately the same temperature at which the 

 absorbed oxygen is given off as noted above. Curve J) (fig. 4) 

 shows one of the time curves taken under these conditions, 

 though it is by no means characteristic of all. In one case for 

 instance with the temperature falling gradually, oxygen began 

 to be given off at about 940°, whereupon the temperature 

 began to rise, and reached 963° in the next five minutes, a 

 violent spitting going on throughout the interval. At the 

 latter temperature the metal became suddenly rigid and closed 

 the porcelain tube through which the oxygen was entering. 



(2) In a Reducing Atmosphere. — Higher results and better 

 defined are obtained by preventing the access of oxygen. We 

 sought to accomplish this first by melting the silver under a 

 layer of common salt and afterward in a plumbago crucible 

 over which a second crucible was inverted as a cover. 



The time curves in both cases, for both melting and solidify- 

 ing points, showed well defined horizontal segments, as may be 

 seen from fig. 4, curves B (under Nad) and C (in graphite). 



Table XVIII contains a series of such observations from 

 which 961*5° is obtained as the melting or solidifying tempera- 



Table XVIII. 

 Melting Point of Silver in Absence of Oxygen. 



Date. 



G. 

 (gr.) 



(Amp.) 



MV. 



t 



Degrees. 



In Porcelain Crucible under NaCl. 



Nov. 33 



400 



5-3 



F 



9023 



961-7° 







10-7 



M 



9026 



961-9 







6-7 



P 



9023 



961-7 







1 1 "3 



M 



9026 



961-9 







In Graphite Crucible. 





Dec. 8 • 



352 



6-7 



F 



9018 



961-2 







9-5 



M 



9019 



961-3 







6-0 



F 



9018 



961-2 







9-3 



M 



9018 



961-2 



ture of pure silver, 

 conditions. 



No spitting was observed under these 



