﻿Chemical Constants of some Diatomic Gases. 993 



hydrogen is probably not satisfactorily covered by formula 

 (16), since the value of C P becomes appreciably reduced 

 within a region of temperature before the value of c for the 

 condensate becomes negligibly small. Hydrogen, therefore, 

 should behave in a manner intermediate between that of a 

 diatomic gas (equation lb') and that of a monatomic gas 

 (equation 7). Nernst * has applied (7) to hydrogen, and 

 after the application of small corrections, has found 

 Cn = —1*23; whereas Langen, by formula (6), finds — 3'767. 

 Equation (16) gives Ch =-2-255 (M = 2*016 ; r = l'34 

 Xl0- 8 cm.). 



8. In the case of gas molecules composed of two different 

 atoms rigidly bound together, the calculation is similar, 

 except that the angle cf> is now, since the molecule is no 

 longer symmetrical, to be taken between the limits and it. 

 In the cases to be considered it is still a sufficient approxi- 

 mation to take K 2 = r 2 . This case is, therefore, covered by 

 the addition of log 2 to (16). In the case of carbon 

 monoxide, r = l'90 x 10~ 8 , M = 28; hence C C0 = 1*205, whilst 

 Langen gives — O'Ol. For nitric oxide, ?* = 1*86 x 10~ 8 , 

 M = 30 ; hence C N0 = 1'263, whilst Langen finds 92. 

 Perhaps all that can be definitely said of Langen's values 

 for these gases is that they are somewhat larger than the 

 value for nitrogen, and it is noteworthy that Nernst's 

 empirical values for the compound gases are larger than 

 those for the elementary gases : 35 for CO and 3*5 for NO, 

 as compared with 2*8 for 2 and 2*6 for N 2 f. 



It is believed that the above method of calculation gives 

 results which are in all cases of the right order, and that 

 the values deduced by other methods are still so divergent 

 that a more searching comparison is not at present possible. 

 It is hoped that the method will shortly be extended to gases 

 with more complex molecules, in which internal motions also 

 occur. If these are considered as small vibrations, their 

 energy can be represented as the sum of squared terms in 

 the coordinates, and the above method can be applied to 

 them without difficulty. 



East London College, 



University of London. 



t Grundlagen des Neuen Wdrmesutzes, 1918, p. 150. There are a 

 few misprints in this section, e.g. in (120) — OoT should be — O'olnT, 

 and (2wm) 1 ' 2 should be (2irmf l2 > 



* Theoretische Chemie, p. 799 (1921). 



