260 Albert P. Mathews 



and with one hydrogen united to the chlorine. I do not wish 

 to lay stress on this point until by a careful determination 

 of the critical data the number of valences in the molecule 

 shall have been exactly determined, but it may be pointed 

 out that, if methyl chloride be written as : 



H \ 



>C = C1 H, 



H/ 



the reason why it decomposes into methylene and hydrochloric 

 acid appears at a glance, since such a double bond is always 

 a source of weakness; and similarly with ethyl chloride, which 

 would be in reality ethylidene chlorhydrate, decomposing into 

 ethylidene and hydrochloric acid. One can also more easily 

 understand in this way the decomposition of chloroform 

 into dichloro- methylene and hydrochloric acid, as the for- 

 mula 



C1 \ 



j | >C = C1 H 



CK 



shows. Phosgen will arise from the dichlormethylene uniting 

 with oxygen. 



The evidence, then, from such various sources as the be- 

 havior, toward light, the diamagnetic properties and cohesion 

 is unanimous that chlorine is polyvalent and not monovalent; 

 many of the chemical and physiological properties of chlorine 

 compounds are also more easily understood on the hypothesis 

 of its trivalency. We may, therefore, conclude that in all 

 these compounds chlorine is trivalent. 



The question which must now be settled is no longer 

 whether chlorine is trivalent, but whether it is ever mono- 

 valent. It is certainly trivalent in most of these compounds 

 in which it was supposed to be monovalent; it is trivalent even 

 in its elemental state. It remains to be seen whether it is 

 ever monovalent. In hydrochloric acid it would appear to 

 be monovalent; but it is exactly here that association takes 

 place. Is it without significance that exactly that compound 

 associates which has but one of the valences of the chlorine 



