496 PRINCIPLES OF CHEMISTRY 



a constant volume) of argon was determined by Kayleigh and Ramsay "by the 

 method of the velocity of sound (see Chapter XIV., Note 7 and Chapter VII., 

 Note 26) and was found to be nearly 1'GG, that is greater than for those gases 

 whose molecules contain two atoms (for instance, CO,H 2 ,N 2 , air, &c., for 

 which" 7c is nearly 1'4) or those whose molecules contain three atoms (for 

 instance, C0 2 ,N 2 0, &c., for which ft is about 1'3), but closely approximate 

 to the ratio of the specific heats of mercury vapour (Kundt and Warburg, 

 fc = 1*67). And as the molecule of mercury vapour contains one atom, so it 

 may be said that argon is a simple gaseous body whose molecule contains 

 one atom. 10 A compound body should give a smaller ratio. The experi- 

 ments upon the liquefaction of argon, which we shall presently describe, speak 

 against the supposition that argon is a mixture of two gases. The import- 

 ance of the results in question makes one wish that the determinations of the 

 ratio of the specific heats (and other physical properties) might be confirmed 

 with all possible accuracy. 11 If we admit, as we are obliged to do for the 

 present, that argon is a new element, its density shows that its atomic weight 

 must be nearly 40, that is, near to that of K = 39 and Ca = 40, which does 

 cot correspond to the existing data respecting the periodicity of the properties 



10 This portion of Rayleigh and Ramsay's researches deserves particular attention as, 

 80 far, no gaseous substance is known whose molecule contains but one atom. Were it 

 not for the above determinations, it might be thought that argon, having a density 20, 

 has a complex molecule, and may be a compound or polymerised body, for instance, N 5 

 or NX n , or in general X n ; but as the matter stands, it can only be said that either (1) 

 argon is a new, peculiar, and quite unusual elementary substance, since there is no 

 reason for assuming it to contain two simple gases, or (2) the magnitude, k (the ratio of 

 the specific heats) does not only depend upon the number of atoms contained in the 

 molecules, but also upon the store of internal energy (internal motion of the atoms in 

 the molecule). Should the latter be admitted, it would follow that the molecules of very 

 active gaseous elements would correspond to a smaller k than those of other gases having 

 an equal number of atoms in their molecule. Such a gas is chlorine, for which k = T33 

 (Chapter XIV., Note 7). For gases having a small chemical energy, on the contrary, a 

 larger magnitude would be expected for k. I think these questions might be partially 

 8e.ttled by determining k for ozone (O 3 ) and sulphur (S 6 ) (at about 500). In other words, 

 I would suggest, though only provisionally, that the magnitude, k = T6, obtained for 

 argon might prove to agree with the hypothesis that argon is N 3 , formed from N 2 with 

 the evolution of heat or loss of energy. Here argon gives rise to questions of primary 

 importance, and it is to be hoped that further research will throw some light upon them. 

 In making these remarks, I only wish to clear the road for further progress in the study 

 of argon, and of the questions depending on it. I may also remark that if argon is NS 

 formed with the evolution of heat, its conversion into nitrogen, N 2 , and into nitride 

 Compounds (for instance, boron nitride or nitride of titanium) might only take place at a, 

 very high temperature. 



11 Without having the slightest reason for doubting the accuracy o f Rayleigh and 

 Ramsay's determinations, I think it necessary to say that as yet (February 1895) I am 

 only acquainted with the short memoir of the above chemists in the ' Proceedings of the 

 Royal Society,' which does not give any description of the methods employed and results 

 obtained, while at the end (in the general conclusions) the authors themselves express 

 some doubt as to the simple nature of argon. Moreover, it seems to me that (Note 10) 

 there must be a dependence of k upon the chemical energy. Besides which, it is not 

 clear what density of the gas Rayleigh and Ramsay took in determining k. (If argon be 

 N 5 , its density would be near to 21.) Hence I permit myself to express some doubt as to 

 whether the molecule of argon contains but one atom. 



