as connected voilk the Theory of Substitutions. 34-3 



portion of the molecule, and occupies the place of the hydro- 

 gen removed. This function is in many instances that of the 

 hydrogen itself, and it is this fact which is the remarkable 

 point in the phaenomena of substitution, that an intensely elec- 

 tro-negative body can act the part of a positive body. It is 

 this fact which is leading chemists to the conclusion, that the 

 properties of compound bodies arise as much from the mode 

 of grouping of their constituent atoms, as from the qualities of 

 those atoms themselves. 



But if it be admitted that the experiments related in this 

 memoir establish the aliotropism of chlorine, then it is plain 

 that a very different, and perhaps satisfactory account, of the 

 phaenomena of substitution may be given. 



As has already been said, no difficulty can arise in account- 

 ing for the removal of hydrogen from organic bodies, or for 

 the first fact just alluded to. This removal will ensue when- 

 ever processes are resorted to which bring the chlorine into an 

 active state. When we expose acetic acid and chlorine to 

 the sun, the latter becomes active, gains the quality of uniting 

 with hydrogen, and chloracetic acid forms. Probably the 

 same change could be brought about by the aid of spongy 

 platina and heat. Upon the second fact, the similarity of 

 function discharged by the chlorine which has replaced the 

 hydrogen atoms with the function of those atoms themselves, 

 a flood of light is thrown by other phaenomena of aliotropism. 

 If a piece of iron be dipped in hydrated nitric acid, though it 

 may be acted on for a few moments, it rapidly becomes pas- 

 sive ; and so with the chlorine atoms which have substituted 

 the hydrogen. In the circumstances under which they are 

 placed they rapidly revert from the active to the passive state. 

 They no longer are endued with an intense electro-negative 

 quality, they have assumed the condition of inactivity. The 

 fact that chlorine in chloracetic acid simulates the functions of 

 hydrogen in acetic acid, is not more remarkable than that 

 iron touched by platina under nitric acid simulates the proper- 

 ties of that noble metal. 



Do not therefore these considerations seem to point out, that, 

 if we admit the fact that simple substances can exist in differ- 

 ent states, in a passive and active form, the phaenomena of sub- 

 stitution are deprived of much of their singularity ? 



Thus, to recall once more the same 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 

 chloracetic acid exhibits a double phaenomenon, — -Ist, the ex- 

 istence of active chlorine expressed by the removal of hydro- 

 gen, activity having been communicated by the rays of the 



