1864.] Dr. Kopp on the Specific Heat of Solid Bodies. 239 



nious plan of Barrett, which is shown to be capable of improvement and 

 extension. Parts of the excellent work of the late Mr. David Jones, * Ta- 

 bles of Life Annuities,' pubhshed under the care and suggestion of the 

 Society for the Diffusion of Useful Knowledge, founded on those ideas of 

 Barrett, are by the author here improved and extended so as to give methods 

 easier for common purposes, and capable of extension to almost all diffi- 

 culties which are likely to occur in the calculation of the value of property. 



II. " Investigations of the Specific Heat of Solid and Liquid Bodies.'^ 

 By Hermann Kopp, Ph.D. Communicated by T. Graham, 

 Esq., Master of the Mint. Received April 16, 1864. 



(Abstract.) ^ 



In the first part the author discusses the earlier investigations on the 

 specific heat of solid bodies, and on the relations of this property to their 

 atomic weight and composition. In this historical report he gives a com- 

 plete analysis of the various opinions published on the subject. 



In the second part the author describes the method he has used for 

 determining the specific heat of solid bodies. This method is based on the 

 method of mixtures. The substance investigated is placed in a glass tube, 

 together with some liquid which does not dissolve it, and the tube is heated 

 in a mercury bath, and then rapidly immersed in a calorimeter containing 

 water. Equalization of temperature takes place rapidly, through the inter- 

 vention of the liquid in the tube. The thermal effect (increase of tempe- 

 rature in the water of the calorimeter) is determined. Preliminary expe- 

 riments give the means of allowing for the thermal effect due to the glass 

 and to the liquid in it, and of thereby obtaining the thermal effect produced 

 by the solid substance. The author gives a complete description of the 

 apparatus and of the mode of using it, and also of the means of determin- 

 ing the ancillary magnitudes which require to be taken into account. The 

 entire method is very simple, and it brings the determination of specific 

 heat out of the restricted sphere of the physical cabinet, with its compli- 

 cated apparatus, within reach of the ordinary appliances of the chemical 

 laboratory. It is also applicable to small quantities, and to such sub- 

 stances as cannot bear a high temperature. The author discusses the 

 possible deficiencies as well as the advantages of this method as compared 

 with those of Neumann and of Eegnault. 



In the third part the author gives his determinations of a very great 

 number of solid bodies. The specific heat of many of them had been 

 determined by Neumann, or by Regnault ; and the almost universal agree- 

 ment of the numbers found by their methods and by his own proved the 

 comparability of his results with those of other physicists. Where there 

 is a considerable difference, the cause is discussed. By far the greatest 



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