[ 466 ] 

 LVI. Intelligence and Miscellaneous Articles. 



ON THE RELATION WHICH EXISTS BETWEEN THE COHESION OF A 

 COMPOUND BODY AND THE COHESIONS OF ITS ELEMENTS. BY 

 M. J. MOUTIER. 



MHIRN has enunciated a general relation which includes the laws 

 * of Boyle and Mariotte and of Gay-Lussac as a particular case. 

 He has shown* that, dividing by the absolute temperature the product 

 of the interatomic volume into the sum of the internal and external 

 pressures, a constant number is obtained for the same body, whatever 

 its physical condition. Thus, if P be the external pressure, R the 

 internal pressure or the cohesion f , V the volume of the body, \p the 

 invariable volume occupied by the atoms, and T the absolute tempe- 

 rature, we have 



(R+PXV-jQ _ constant . 



I have endeavoured J to establish, independently of any hypothesis 

 as to the nature of thermal phenomena, that this constant is equal 

 to half the product obtained by multiplying the mechanical equiva- 

 lent of heat E by the quantity of heat necessary for raising the body 

 through one degree, independently of any external or internal work. 

 Calling M the weight of the body, K its absolute specific heat inde- 

 pendently of the physical condition, the preceding relation may then 

 be written 



(R + PKV-^MKB, 



or 



MK= g(R + P)(V-fl 

 TE 



This quantity MK represents the quantity of heat necessary to raise 

 the body one degree, independently of any external or internal work, 

 or, if we like, the quantity of heat necessary to raise the temperature 

 of the atoms through one degree. 



Connecting with this relation the law of the absolute specific heats 

 of compound bodies, we get a relation between the cohesion of a 

 compound body and the cohesions of its elements at the same tem- 

 perature. 



Suppose that the two bodies A and A', both under the pressure P 

 and at the temperature T, combine, forming a body C which we sup- 

 pose to be under the same conditions of temperature and pressure. 

 Let R and R' be the cohesions of the two bodies A and A', V and 

 V' their volumes, \p and \p' the invariable volumes occupied by the 



* Exposition Analytique et Experiment ale, 1865, p. 106. 

 f G. A. Hirn, Annates de Chimie, 4th series, vol. xi. p. 90. 

 X Comptes Rendus, vol. lxiv. p. 653. 



