304 THE ALLOTROPISM OF CHLORINE. [MEMOIR XX. 



show that that opinion rests on something more solid 

 than conjecture. The habitudes of many of the gaseous 

 bodies strengthen this conclusion. Oxygen refuses to 

 unite when mixed with hydrogen precisely in the man- 

 ner of chlorine, and it requires a certain modification to 

 be made in the electro-negativ 7 e element before water or 

 hydrochloric acid can result. 



Just, therefore, in the same manner that so many ele- 

 mentary bodies can put on under the influence of exter- 

 nal causes an active or passive condition, I infer, as the 

 result of the experiments brought forward in this Mem- 

 oir, that chlorine is one of these allotropic bodies, having 

 a double form of existence. That, as commonly prepared, 

 it is in its passive state; but that on exposure to the 

 indigo rays or other causes it changes and assumes an 

 active form. That, in this latter state, its affinity for 

 hydrogen becomes so great that it decomposes water 

 without difficulty, as in the experiment which this Mem- 

 oir is designed to illustrate. 



On the Relation of the Preceding Conclusions with the 

 Theory of Substitutions. 



Having thus explained the facts which appear to indi- 

 cate the allotropism of chlorine, I shall now offer some 

 considerations on its connection with the theory of sub- 

 stitutions of M. Dumas. 



Admitting the fact that the electro-negative qualities 

 of chlorine are exalted upon its exposure to the indigo 

 rays, and that the resulting effect is not a temporary 

 change, but one lasting for a considerable period of time, 

 we can give a very plain and simple account of the de- 

 composition of water by this gaseous substance under 

 the influence of sunshine. 



On the same principle that a mixture of chlorine and 

 hydrogen may be kept in the dark without union for a 



