98 Mr. J. J. Waterston on certain Thermomolecular 



multiplying this value of C by ©, the vapour-density or molecular 

 weight (not atomic weight) of the body, we obtain a number that 

 represents the cohesive integral of a molecule of that body at the 

 t temperature. 



Performing this computation for several bodies and comparing 

 the numbers with the respective values of h and of //,, if it is 



found that they follow the same ratio, that — is a constant 



quantity at the t temperatures of the several liquids, the legiti- 

 mate inference to be drawn is that the cohesive force of each 

 molecule is proportional to its volume //. when in the liquid state. 



This is equal to -, the quotient of vapour-density by spec. grav. 

 at t, and hence — = Cs is constant in the group of liquids. The 



r" 



following is the computation. 



Muriatic Ether. — At pp. 912, 914 of Regnault's second volume 

 we have two values of X: one at + 12°*2 is 97'70; another at 

 — 7°*2 is 95-88. The t temperature of this body being 0°, we 

 have X at 0° = 96*60 = C in this case, as Q = 0. The vapour- 

 density is 32| = © and C© = 3115, which, divided by h = 144, 



gives 21*63 as the value of the quotient — • 



lb 



Hydriodic Ether.— X = 53*20 at -5°, and 58-9 at 71°. The 

 t temperature is 62°*4, at which (p. 278) Q = 10*4, and X = 58*3 ; 



hence C = 47'9, © = 78, h=177, ^ =21-11. 



Chloroform.— At p. 836, X = 74*00 at 51°*4, the r tempera- 

 ture, and Q= 12*07 (p. 276); hence C = 61-9. And since © = 60, 



A=17L we have ^ =21 '71. 

 h 



Sulphuric Ether has - =3*00 instead of 4*11, the value com- 



fj, > 



mon to the three preceding liquids ; nevertheless the cohesion- 

 integral of its liquid molecule has the same ratio to h. Its t 

 temperature is 24°, at which Q= 12*86 (p. 275) and X = 105*2 



(p. 820); hence C = 92-3 and© = 37, h= 156*7 gives ^=21*79. 



Hi 



The mean of the four values is 21*56. 



In the same way the quotient was computed for the bichloride 

 of carbon 20*2, sulphide of carbon 21*1, turpentine 19*1, chlo- 

 ride of phosphorus 20*0. 



§ 46. It seems probable that this value of ~j- is the same for 



lb 



