The Valence of Chlorine 261 



satisfied by another monovalent atom? Is it not rather more 

 probable that this is the cause of its association, the other 

 two valences being not closed, but out and active? The com- 

 putation actually shows that the chlorine is here also tri- 

 valent. I know of no means of telling whether it is mono- 

 valent or trivalent in sodium chloride. But it is not impos- 

 sible that sodium chloride itself is a highly associated sub- 

 stance. Furthermore, its power of adding iodine indicates 

 that the chlorine may be trivalent. Friend also states that 

 sodium chloride may be Na Cl =C1 -- Na. 



Concerning the valence of the other halogens, the facts 

 are too scanty and the data too unreliable to draw a conclu- 

 sion from the cohesion, except perhaps in the case of elemental 

 bromine, which appears to be univalent. The critical data 

 of brombenzene and iodobenzene were not directly deter- 

 mined by Young, but computed from the temperature, pres- 

 sure and density curves. I do not believe that they are en- 

 tirely trustworthy, since the number of valences found in the 

 molecule is too small even if these halogens are considered 

 monovalent, unless the carbon be here trivalent, and this 

 does not seem possible. T c and V c of ethyl iodide, I com- 

 puted from Ramsay and Shields' surface-tension determina- 

 tions, and this computation is not very accurate. Hence I 

 do not attach much weight to the cohesional evidence of the 

 valence of any of these compounds of bromine and iodine. 

 There are no indications, however, that they are polyvalent. 

 That they are polyvalent is, however, indicated from their 

 action on light, their diamagnetic properties and many of 

 their chemical properties. Inasmuch, however, as the re- 

 fraction method is not very satisfactory for determining 

 valence, the question of the valence of these substances must 

 be left open, with the probability that they will be found to be 

 polyvalent like chlorine. 1 



1 The fact that bromine is monovalent in its elemental state may account 

 for its relative inertness and is confirmed by its dissociation at high tempera- 

 tures, when the atoms have been shown to have but one active valence. See 

 Friend: "The Theory of Valence," 1909, p. 18. 



