^" 3*4 Prof. Draper on the 'Allotropisvi of Cklori?ie, 



'sun, or by some other appropriate method; 2nd, the existence 



'of passive chlorine in the particles of chloracetic acid. 



ihuiy consider, that were no other instances known, the two 



-'eases cited by Berzelius of the double forms of silicic acid and 

 arsenious acid establish the fact, that a given allotropiccondi- 



' tion may be continued by an elementary atom when it goes 

 into union with other bodies. And I regard the various cases 



■ in which hydrogen is replaced by iodine, bromine, &c., in 

 which in the resulting compound those energetic electro-ne- 

 'gative elements fail to give any expression of their presence 

 and activity, as analogous to other common and too much 



- overlooked facts. Chlorine which is in the dark may be kept 

 in contact with hydrogen without exhibiting any of its latent 

 energies. Touched by an indigo ray it instantly assumes the 

 active state, and a violent explosion is the result. 



To use therefore the same nomenclature to which Berzelius 

 has resorted in the case of other allotropisms, we may desig- 

 nate the ordinary form of chlorine, procured by the action of 

 chlorohydric acid on peroxide of manganese, as Cl/3, and 

 admit that this passes into the condition Ci« by the action of 

 the solar rays, contact of platina, or a high temperature; and 

 that in any case of substitution, the hydrogen is removed under 

 the condition CI «, and the resulting compound molecule con- 

 tains Cl/3; the assumption of the passive state disguising the 

 presence of the electro-negative atom. 



The explanation here given of the phaenomena of substitu- 

 tion involves the position, that chlorine, when brought in rela- 

 tion with carbon, under certain circumstances, is thrown into 

 the passive state, — the state CI |3. We naturally look for di- 

 rect evidence that this is the case. It seems to me that there 

 are many well-known chemical facts v^hich tend to establish 

 this passive condition. In the first case to which we turn, the 

 chlorides of carbon, the inactive state is established in a stri- 

 king manner. The affinity which exists between chlorine and 

 carbon is apparently feeble, yet when these bodies have once 

 united, the chlorine is brought into such a condition that it 

 has lost the quality of being detected by the ordinary tests 

 which determine its presence. How strongly does this con- 

 trast with the case of chlorohydric acid ! a feeble affinity unites 

 carbon and chlorine, and intense affinity unites hydrogen and 



V chlorine ; yet in the former case the chlorine is undiscoverable 

 by the most common tests, in the latter it yields to them all. 

 And the causes are obvious ; in the one case it is in the pas- 

 sive, in the other in the active condition. 



I have hitherto spoken of the active and passive states as 

 though they were fixed points in elementary bodies, and as 



