284 THE ALLOTKOPISM OF CHLORINE. [MEMOIR XX. 



MEMOIR XX. 



ON THE ALLOTKOPISM OF CHLOEINE AS CONNECTED WITH 

 THE THEOEY OF SUBSTITUTIONS. 



From the American Journal of Science and Art, Vol. XLIX. ; Philosophical Mag- 

 azine, Nov., 1845. 



CONTENTS : Chlorine exists in two states, active and passive. Decompo- 

 sition of water by it in the sunlight. Facts connected with this de- 

 composition. The relations of chlorine and hydrogen. The allotro- 

 pism of chlorine. Connection of these facts with the theory of substi- 

 tutions. 



THE researches of M. Dumas on chemical types have 

 shown that between chlorine and hydrogen remarkable 

 relations exist, indicating that the electrical characters 

 of elementary atoms are not essential, but rather inci- 

 dental properties. The extension of these researches 

 has given much weight to the opinion that the electro- 

 chemical theory may be regarded as failing to account 

 for the replacement of such bodies as hydrogen by chlo- 

 rine, bromine, oxygen, etc. I do not know that as yet 

 any direct evidence has been offered that the electrical 

 character of an atom is not an essential quality, but one 

 that changes with circumstances. It appears to be 

 rather a matter of inference than of absolute demonstra- 

 tion. 



It is the object of this Memoir to furnish such direct 

 evidence, and to show that chlorine, the substance which 

 has given rise to the discussions connected with the 

 theory of substitutions, under the very circumstances 

 contemplated, has its electro-chemical relations changed. 



More than two years ago I brought before the British 



