42 AKGON, A NEW CONSTITUENT OF THE ATMOSPHERE. 



ill tlie gas, both expressed as heat ; L\. is caused both by molecular and atomic 

 iiiDtiou. Now as the specitic heats arc practically independent of temperature, 



H,-H„ C. 



IIj — IIq = C,., or si)ecific heat at constant volume; and K, — K^. which may be 

 teiined M, is the proportion of this heat which is employed in [iroducing and 

 main tain ill" translatioual motion of the molecules. Therefore 



o 



M i (C„ - Cv) Cp - C>. 2 



— = ; and = — 



C, C, M 3 



In words, the heat used in expanding the gas bears to the heat producing molecular 

 motion 2:3. Hence the ratio M = | X 2.00 = 3.00. The specific heat of the 

 molecular weight taken in grammes of a uKuiatoinic gas is therefore 3.00 calories for 

 constant volume, and for constant jn-essure, 3.00 + 2.00 = 5.00. The ratio between 

 these numbers is 1 : 1.66; and tliis latio has been fouml experimentally for mercury 

 gas by Kundt and Warburg (Joe. c/'f.). That it has also been found for argon is 

 equally a proof of the monatomic nature of its molecules. A nioiiatomic gas can 

 only be an element, or a mixture of elements, and hence it follows that argou is 

 not of a compound nature. 



Fi-om Avogadro's law, the density of a gas is half its molecular weight ; now 

 the density of aigon is a[)[iroxiniately 20, hence its molecular weight must be 40. 

 But its molecule is identical with its atom ; hence its atomic weight, or, if it be a 

 mixture, the mean of the atomic weights of the constituents of that mixture, ivgard 

 being had to the pioportion in which they are present, must be 40. 



Chemists will recognize this fact ivs of the most startling nature ; but the 

 data are clear, and we can only weleonie any confirmation by independent 

 experimenters. 



We are not yet able to state with certainty whether aigon is a mixture, or, if 

 it be, of how many elements it consists. The spectroscojtic evidence points in 

 favor of at least two components ; but of itself it is not conclusive. Attempts will 

 be made to effect a separation, if possible, of tlie elements wliicli give such dis- 

 similar spectra, when tin; current passes from positive to negative, or in the 

 conti-ary direction. But, as yet, time hjis not allowed of any expeiiments with such 

 an object. 



The relation of argon to other elements remains to be discussed. We inclined 

 for long to the view that it (or they) was possibly the representative of the three 



