burgess: melting points of elements 17 



table represents an attempt to assign the most probable values to 

 the several melting points from a consideration of all the data 

 available, and is a revision of the list in the new Smithsonian 

 Physical Tables. 



In so far as possible, the values are reduced to a common tem- 

 perature scale, that given by the gas thermometer. In general, 

 differences between the various gas scales as recently deter- 

 mined and the thermodynamic scale are less than the uncer- 

 tainties of reproducibility by any one method. For example, 

 the four observations on the melting point of gold, by the constant 

 volume nitrogen thermometer, published within the past ten 

 years, range from 1059.3° to 1067.2° C, and the correction to the 

 thermodynamic scale is here 1° or less. Besides the direct 

 gas thermometer determinations, there are, also, for many of the 

 melting points, precise, differential checks made by electrical 

 resistance, thermo-electric, or optical thermometers. The differ- 

 ence between the melting points of gold and copper is thus known 

 to be 20° C. by auxiliary methods more closely than these tem- 

 peratures have usually been independently located by the gas 

 thermometer. 



For the range 100° to 500° C, the scale here adopted agrees 

 with the value 444.7 for the sulphur boiling point, a temperature 

 that has been many times determined, and which is perhaps the 

 best known fixed point above 300°. 



For high temperatures, the scale is satisfied very exactly by 

 taking c 2 = 14,500 in the formula for Wien's law connecting /, 

 monochromatic luminous intensity, and T, absolute temperature : 

 log I/I x = c 2 X log e (1/7 7 ! - l/T). This agrees well with the 

 gas thermometer measurements of Day and Sosman in the range 

 1000° to 1550° C. The use of Wien's law possesses the theoretical 

 advantage for extrapolation beyond 1550° in giving the thermo- 

 dynamic scale. 



In the table, elements whose melting points are well known or 

 used as standards are printed in capitals. An idea of the exact- 

 ness of our knowledge of some of the melting points is also given. 





7 



