254 Albert P. Mathews 



known that sodium chloride will add iodine, presumably by 

 the extra valences of the chlorine. 1 



There is good ground, therefore, for doubting whether 

 chlorine is ever monovalent. This question can be tested 

 easily by the cohesion method. 



Before proceeding to the actual computations it must 

 be decided whether the cohesion method detects only valences 

 actually employed in binding atoms together, or stretching 

 between the atoms; or whether it detects in addition the re- 

 serve valences; and also valences which do not extend to 

 atoms, but which are open, in an active form, and ready to 

 combine if the opportunity arises. It is clear from my former 

 paper that concealed, polarized, resting or reserved valences 

 do not play any part in cohesion ; or, at any rate, they are not 

 to be counted in the number of valences affecting the cohesion. 

 Thus oxygen has certainly two reserve valences which are 

 usually in an inactive or resting state. In many compounds 

 examined, not more than two valences could be attributed 

 to the oxygen as affecting its cohesion. These two reserve 

 valences played no role as long as they were inactive. Sim- 

 ilarly, nitrogen has the power of opening up at least seven 

 valences, but it was actually found that only one, two or 

 three valences played a role in the cohesion of the nitrogen 

 compounds, depending on how many active valences the atom 

 had. The reserve, or inactive, valences played no part. 

 Carbon is usually quadrivalent, but it is suspected of having 

 the power of becoming hexavalent; but the number of valences 

 active in carbon compounds was always two, or four. If 

 these reserve valences of carbon exist they do not affect 

 cohesion. Sulphur, too, although it may be hexavalent, has 

 only four of its valences playing a part in the cohesion of sulphur 

 dioxide; the two reserve valences are inactive on the cohesion. 



It is clear, then, that the cohesion does not detect, and 

 consequently it is not affected by, those reserve valences 

 which are polarized, or resting, or, which are, as it were, 

 like antennae, withdrawn or folded, within the atom. 



1 See Friend: "The Theory of Valency," London, 1909, pp. 58 et seq. 



