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VI. The Specific Heats of Metals and the Relation of Specific Heat to Atomic 



Weight. Part III. 



By W. A. TILDEN, D.Sc., F.R.S., Professor of Chemistry in the Royal 



College of Science, London. 



Received March 9, Read March 17, 1904. 



THE law of NEUMANN assumes that when an atom enters into chemical combination it 

 retains the same capacity for heat as when in the nncombined or elemental state. 

 This generalisation is, however, based on the values observed for the mean specific 

 heats of elements and their compounds between and 100 (!.* 



Attention was directed in Part II. of this invest igationt to the great differences 

 found in the influence of temperature on the specific heats of various metals, such as 

 aluminium on the one hand, and silver or platinum on the other. The experiments 

 now about to be described were undertaken with the object of ascertaining to what 

 extent these differences persist in the compounds of such elements. 



If the calculated atomic heats of elements in combination are equal at various 

 temperatures through a considerable range to the sum of the atomic heats of the same 

 in the separate state at the same temperatures, then the difference between any two 

 must be due to a fundamental difference in the atoms of the elements concerned and 

 not to a difference in their states of aggregation when separate. 



The specific heats of nickel sulphide and silver sulphide have already been compared 

 through a range of temperature from 182 to + 324 C., but owing to the low 

 melting-point of sulphur, arid especially to the occurrence of several allotropic 

 modifications of this element in the solid state, it was not thought worth while to 

 attempt determinations of its specific heat at various temperatures for this purpose. 



The only element which seemed to present the assemblage of characters required 

 for the purpose contemplated was tellurium. I am indebted to Dr. T. K. ROSE for a 

 supply of tellurium which had already been refined by several dissolutions in aqua 

 regia and precipitation by sulphurous acid. It was further purified by fusion with 

 potassium cyanide, solution in water, and precipitation by exposure to air. 

 Compounds of silver, nickel and tin with tellurium were made by the following 



* REGNAULT, 'Ann. Chim, Phys.' [3], 1, 129; KOPP, 'Phil. Trans.,' 1865. 

 t 'Phil. Trans.,' A vol. 201, p. 37 (1903). 

 (364.) T 2 27.5.04 



