Properties of Matter in the Liquid and Gaseous States. 83 



a=0-005499 from 6°-05 to 63°-79. 

 *=0*005081 from 63°*79 to 100°*1. 

 From series B, with the corresponding unit volume at 6°-62 and 

 31*06 atmospheres, we find : — 



a=O006826 from 6°- 62 to 63°*83. 

 a=0-005876 from 63°-83 to 100°-64. 

 And in like manner from series C with the unit volume at 

 6°-01 and 40*06 atmospheres :— 



a=0*009481 from 6°*01 to 63°*64. 

 a=0*007194 from 63°-64 to 100°-60. 

 The coefficient of carbonic acid under one atmosphere referred 

 to a unit volume at 6° is a== o-003629. 



From these experiments it appears that the coefficient of ex- 

 pansion increases rapidly with the pressure. Between the tem- 

 peratures of 6° and 64° it is once and a half as great under 22 

 atmospheres, and more than two and a half times as great under 

 40 atmospheres, as at the pressure of 1 atmosphere. Still more 

 important is the change in the value of the coefficient at different 

 parts of the thermometric scale, the pressure remaining the same. 

 An inspection of the figures will also show that this change of value 

 at different temperatures increases with the pressure. 



Another interesting question, and one of great importance in 

 reference to the laws of molecular action, is the relation between 

 the elastic forces of a gas at different temperatures while the volume 

 remains constant. The experiments which I have made in this part 

 of the inquiry are only preliminary, and were performed not with 

 pure carbonic acid, but with a mixture of about 11 volumes of car- 

 bonic acid and 1 volume of air. It will be convenient, for the sake of 

 comparison, to calculate, as is usually done, the values of a from these 

 experiments ■ but it must be remembered that a here represents no 

 longer a coefficient of volume, but a coefficient of elastic force. 

 Elastic force of a mixture of 11 vol. C0 2 and 1 vol. air heated 



under a constant volume to different temperatures. 

 Vol. C0 9 . 



366-1 

 366-2 

 366-2 

 256-8 

 256-8 

 256-8 



Temperature. 



Elastic Force. 







at. 



13-70 



22-90 I 



40-63 



25-74 L . 



99-73 



31-65 J 



13-70 



31-18 1 



40-66 



35-44 [ . 



99-75 



44-29 J 



(A) 



(B) 



From series Awe deduce for a unit at 13°-70 and 22*90 atmo- 

 spheres :— a=0*004604 from 13°*70 to 40°-63. 

 a= 0*004367 from 40°-63 to 99°«73. 

 And from series B : — 



a= 0-005067 from 13°-70 to 40°-66. 



a= 0-004804 from 40°-66 to 99°-75. 



The coefficient at 13°-70 and 1 atmosphere is a=0-003513. 



It is clear that the changes in the values of a, calculated from 



the elastic forces under a constant volume, are in the same direction 



as those already deduced from the expansion of the gas under a 



