[ 47 ] 



II. The Influence of Temperature on the Specific Heat of 

 Aniline. By E. H. Griffiths, M.A* 



[Plates I. & II.] 



OUR knowledge of the effect of changes of temperature 

 upon the specific heat of substances is limited. The 

 reason of this is evident, for, in addition to the difficulties of 

 thermometry, the experimental methods usually adopted are 

 based on comparisons in which water is used as a standard, 

 and our knowledge of its capacity for heat at different tem- 

 peratures is far from satisfactory. The conclusions of Rowland 

 (1879), of JBartoli and Stracciati (1893), and my own 

 investigation completed in 1892, all point to the fact that the 

 specific heat of water diminishes as the temperature rises to 

 20° C, at which temperature Bartoli and Stracciati find it is 

 a minimum. My observations did not extend beyond 27° C, 

 up to which temperature I found no signs of a minimum, 

 which Rowland places at about 34° C. When such discre- 

 pancies exist with regard to the standard, it is not surprising 

 that the conclusions arrived at regarding other substances are 

 unsatisfactory. 



For other reasons water is by no means an ideal standard 

 for calorimetry. Its capacity for heat is so great that the 

 changes in temperature caused by the immersion in it of 

 bodies whose specific heats are small are too minute to be 

 measured with exactness under ordinary circumstances. 

 The difficulty is surmounted in practice by causing the 

 immersed body to cool through a considerable range. Other 

 errors are, however, introduced by this method, for the 

 transference of the hot body into the cool water can rarely be 

 conducted without loss of heat. What we require is a liquid 

 of small capacity for heat whose temperature-coefficient of 

 specific heat is accurately known. It should also, if possible, 

 be a liquid easily obtainable in a fairly pure state and should 

 have a low vapour-pressure at ordinary temperatures. I 

 believe that in Aniline we possess such a liquid, and I hope to 

 be able to adduce sufficient evidence to lead to the conclusion 

 that its specific heat is now known with considerable accuracy 

 over a range of 15° to 52° 0. 



The method I have adopted is an old one, viz. a supply of 

 heat to the interior of the calorimeter by means of an im- 

 mersed conductor whose ends are kept at a constant potential- 

 difference. I admit that there are difficulties inseparable from 



* Communicated by the Physical Society : read October 26, 1894. 



