Thermo-electric Interpolation Formulce. 



Table X, 

 Barus Melting and Boiling Points. 



487 





Computed 

 by Eq. 3. 



Computed 

 by Log. Eq. 



Data by other Observers. 



Mercury (B. Pt.) 

 Zinc 



o 

 357 

 420 

 446 

 638 

 694 

 782 

 929 

 986 



1091 



1096 



1435 

 1476 



1585 

 1757 



359 

 423 

 449 

 641 

 697 

 782 

 926 

 985 



1090 



1095 



1441 



1485 

 1597 

 1783 



356-76 

 417-57 

 444-53 

 635 



930 



968 



954 

 1072 

 1035 

 1082 

 1054 



1450 

 1500 

 1775 



Callendar and Griffiths. 

 i> »> 

 >) >> 



Le Chatelier. 



Deville and Troost. 



Holborn and Wien. 



Violle. 



Holborn and Wien. 



Violle. 



Holborn and Wien. 



Violle. 



Carnelly and Williams. 



Violle. 



Violle. 



Sulphur (B. Pt.) 



Aluminium 



Selenium (B. Pt.) 

 Cadmium (B. Pt.) 



Zinc(B. Pt.) 



Silver 



Gold 



Copper 



Bismuth 



Nickel 



Palladium 



Platinum 





Remark. 



Review of the laborious researches which have been devoted 

 to the direct comparison of thermo-electric elements with the 

 air thermometer, mainly for the purpose of advancing the 

 art of pyrometry, has enforced the conviction that, at least 

 for the immediate future, this end would be better served by 

 accurate gas-thermometer measurements of melting-points of 

 metals. Each such determination made upon a reducible 

 metal of known high purity under proper reproducible con- 

 ditions fixes an enduring and reproducible reference-point, 

 a pyrometric " bench mark." And there are enough inex- 

 pensive metals, together with a possible system of simple 

 alloys, to give points of sufficient frequency. These would 

 then afford a convenient means of obtaining accurately known 

 high temperatures for purposes of study of all high temperature 

 phenomena, and particularly for calibrating thermo-electric, 

 electrical resistance, optical, or other secondary pyrometric 

 interpolation apparatus, — for it must be remembered that all 

 such apparatus is necessarily secondary, the gas thermometer 

 being inevitably the primary. 



On the other hand, comparison with the air thermometer of 

 a thermo-couple, or of a resistance pyrometer, or the study of 



