304 Mr E. H. Griffiths, On the 'Volume Heat' of Aniline. [May 18, 



employed by Bunsen are less affected by changes in the capacity 

 for heat of water, but, on the other hand, they involve some 

 assumption as to the ratio of the " mean thermal unit " to the 

 thermal unit at other temperatures. 



While these doubts exist regarding the standard, the data 

 obtained by the comparison of other bodies with that standard 

 are of little absolute value. 



In the Philosophical Magazine for January, 1895, I have given 

 an account of some observations on the specific heat of aniline 

 over the temperature range 15° to 52° C. To whatever objections 

 the method there described may be open, it is certain that the 

 values there given are independent of any assumption as to the 

 capacity for heat of water. The following facts may, therefore, 

 be of some interest. 



During last autumn Mr C. Green, of Sidney Sussex College, 

 was so kind as to make for me a series of determinations on the 

 density of aniline over the above temperature range. The instru- 

 ment used was Sprengel's Pyknometer. I can from personal 

 observation answer for the care with which the observations were 

 made. The expansion of the glass was determined by a series of 

 preliminary experiments, and three independent sets of determi- 

 nations gave the following values for the density of Aniline. 



Table I. 



One determination only was made at 20°. 



If we multiply the capacity for heat at different temperatures 

 by the density at those temperatures, we get the capacity for heat 

 of equal volumes, a quantity which I propose to distinguish by the 

 term "volume heat." 



In the following table, col. ii (extracted from page 77 of the 

 paper above referred to) gives the values of the specific heat (S^) 

 of Aniline at temperatures 0^. 



Column III gives the density (d^) at the same temperature as 

 determined by Mr Green. 



Column IV gives the " volume heat." 



