THE VALENCE OF OXYGEN, SULPHUR, NITROGEN 



AND PHOSPHORUS DETERMINED FROM THE 



MOLECULAR COHESION 



BY ALBERT P. MATHEWS 



i. The valence of oxygen 



In my paper on the relation of molecular cohesion to 

 molecular weight and valence, 1 in which the number of valences 

 were computed from the value "a" of van der Waals' equa- 

 tion, I considered oxygen to be bivalent except in the case of 

 oxygen gas. The question of the quadri valence of oxygen 

 was not taken up, because I wished to get the main point of 

 the connection of valence and cohesion well established be- 

 fore discussing particulars. But as it is believed by many 

 that oxygen is at times quadrivalent and as this possibility 

 has such an important bearing on theories of association and 

 solubility and, indeed, on the ionizing powers of water, and 

 is also full of importance in physiology, it is interesting to 

 examine the oxygen compounds of that table for evidence 

 in favor of tetravalence. 



One atom of oxygen is supposed by Stieglitz, Arm- 

 strong, and Goldschmidt 2 to be quadrivalent in the esters. 

 In the first table, therefore, I have incorporated the results 

 of a determination from the molecular cohesion by the usual 

 formula :n == a 3/2 X 3.2 X io 5 /(mol. wt.), of the total number 

 of valences per molecule, and compared it with the number of 

 valences computed if one oxygen is quadrivalent. I have 

 taken only those esters whose critical data were recently 

 very carefully determined by Young. All of these esters 

 associate a little at low temperatures, but their vapors are 

 normal for some degrees below the critical temperature, 

 except possibly that of methyl formate. 



1 Mathews: Jour. Phys. Chem v 17, 181 (1913). 



2 Zeit. Elektrochemie, 10, 221 (1904). 



