THE VALENCE OF THE ARGON GROUP AS DETER- 

 MINED FROM THE MOLECULAR COHESION 



BY ALBERT P. MATHEWS 



The valence of the argon group of elements is one of the 

 most interesting problems in chemistry. They are very 

 generally regarded as zero valent, chiefly owing to the posi- 

 tion they take in the periodic system between strongly electro- 

 positive and electro-negative, univalent elements. That they 

 are monatomic is undoubted, but they might be monatomic, 

 like mercury vapor, and still have valence. Ramsay 1 made 

 the suggestion, indeed, that they combine into molecules 

 at other than ordinary temperatures. To account for the 

 atomic weight of argon, which computed from the density is 

 39.9 if the gas is monatomic, he suggested that argon is a 

 mixture of many monatomic molecules with a few diatomic 

 molecules. The ratios of the specific heats as determined is 

 1.659; whereas if there were 5 percent of diatomic molecules 

 it would be 1.648. The theoretical number, if the gas is 

 entirely monatomic, is 1.667. After discussing this possi- 

 bility, however, Ramsay says: ''But on the whole the pre- 

 sumption is against the hypothesis that argon is a mixture 

 of monatomic and diatomic molecules." 



There is some evidence that argon is not entirely lacking 

 in chemical affinity. Berthelot, 2 by the action of the electric 

 discharge on a mixture of argon and benzene vapor, or of 

 argon and carbon bisulphide, produced a brownish deposit 

 on the glass from which argon could be reobtained. Ramsay, 3 

 in commenting on the absence of the argon lines in the sun's 

 spectrum, suggests, as a reason, that it enters into combina- 

 tion only at high temperatures, these compounds being 

 endothermic; and he cites 4 several observations indicating 



1 Ramsay: "Gases of the Atmosphere," London, p. 231 (1902). 



- Berthelot: Comptes rendus, 120, 581, 660, 1316 (1895); 124, 113 (1897). 



3 Ramsay: Loc. cit., p. 261. 



4 Ramsay: See footnote, p. 538, to article by C. Trenton Cooke: Zeit. 

 phys. Chem., 55, 537 (1906). 



