308 THE ALLOTROPISM OF CHLORINE. [MEMOIR XX. 



the phenomena of substitution are deprived of much of 

 their singularity. 



Thus, to recall once more the example to which I have 

 before referred, and which has been so well illustrated 

 by the researches of M. Dumas, the transmutation of 

 acetic into chlor-acetic acid exhibits a double phenom- 

 enon. 1st. The existence of active chlorine, expressed 

 by the removal of hydrogen, activity having been com- 

 municated by the rays of the sun, or by some other ap- 

 propriate method. 2d. The existence of passive chlorine 

 in the particles of chlor-acetic acid. 



I consider that, were no other instances known, the 

 two cases cited by Berzelius of the double forms of silicic 

 acid and arsenious acid establish the fact that a given 

 allotropic condition 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 iedine, bromine, etc., in which, in the resulting com- 

 pound, those energetic electro-negative 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 allotropisins, 

 we may designate the ordinary form of chlorine made 

 by the action of hydrochloric acid on peroxide of man- 

 ganese as Cl/3, and admit that this passes into the con- 

 dition Cla by the action of the solar rays, contact of plat- 

 inum, or a high temperature; and that in any case of 

 substitution the hydrogen is removed under the con- 

 dition Cla, and the resulting compound contains Cl/3, 



