328 Prof. Draper 07i the Allotropism of Chlorine^ 



More than two years ago I brought before the British As- 

 sociation some of the facts. They were subsequently published 

 in the Philosophical Magazine, in a memoir on " Tithonized 

 Chlorine," July 1844'), The connexion of these experiments 

 with the discussion between the theory of substitutions and 

 the electro-chemical theory is obvious. 



Very recently M. Berzelius has published an important 

 paper on the Allotropism of Simple Bodies *, the object of which 

 is to point out that many of those bodies can assume different 

 qualities by being subjected to certain modes of treatment. 

 Thus carbon furnishes three forms — charcoal, plumbago and 

 diamond. 



To a certain extent these views coincide with those which 

 have offered themselves to me from the study of the properties 

 of chlorine. They are not, however, altogether the same. M. 

 Berzelius infers that elementary bodies can, as has been said, 

 assume under varying circumstances different qualities. The 

 idea which it is attempted to communicate in this memoir is 

 simply this ; that a given substance, such as chlorine, can pass 

 from a state of high activity, in which it possesses all its well- 

 known properties, to a state of complete inactivity, in which 

 even its most energetic affinities disappear; and that between 

 these extremes there are innumerable intermediate points. 

 Between the two views there is therefore this essential differ- 

 ence ; from the former it does not appear what the nature of 

 the newly-assumed properties may be; from the latter they 

 must obviously be of the same character, and differ only in in- 

 tensity or degree, diminishing from stage to stage until com- 

 plete inactivity results. 



In the case of chlorine, the same activity which is commu- 

 nicated by the indigo rays can also be communicated by a high 

 temperature, or by the action of platina. The term " titho- 

 nized chlorine," which I formerly used, is therefore too re- 

 stricted, and indeed in this view of the case improper. The 

 simple appellations active and passive, are perhaps the best, 

 and I shall therefore employ them. 



The points which this memoir is intended to establish are, — 



I. That chlorine gas can exist under two forms. In the 

 same way that metallic iron can exist as active or passive iron, 

 chlorine can assume the active or passive state. 



II. Having established the fact of the allotropism of chlo- 

 rine, I shall then show its connexion with the Theory of Sub- 

 stitutions of M. Dumas, and how the most remarkable points 

 in that theory may be easily accounted for. 



The time perhaps has not yet arrived for offering a com- 



* A translation of this paper was published in Taylor's Scientific Me- 

 moirs^ part xiv., 1845. — Ed. 



