362 Prof. Draper on the Allotropism of Chlorine 
such as a slight elevation of temperature and the contact of cer- 
tain bodies. ‘Thus iron, which is so easily oxydized under ordi- 
nary circumstances, appears to lose its affinity for oxygen after 
it has been touched under the surface of nitric acid by a piece 
of platina. It then puts on the attributes of a noble metal, and 
simulates the properties of platina and gold. 
This remarkable instance of the passage from an active to a 
passive state, as Berzelius remarks, may lead to a conjecture re- 
specting the true condition of certain gases. No one can reflect 
on the inactivity of nitrogen gas under ordinary circumstances, 
contrasted with its equally extraordinary activity as a constituent 
of organic bodies, without being struck with the apparent con- 
nexion of that phenomenon with these of allotropism. And 
though Berzelius with his customary caution merely insinuates 
that nitrogen can exist under two forms; the facts which are 
here developed in relation to chlorine appear to show that that 
opinion rests on something more solid than conjecture. 'The 
habitudes of many of the gaseous bodies strengthen this conclu- 
sion. Oxygen gas refuses to unite when mixed with hydrogen 
precisely in the manner of chlorine, and it requires a certain 
modification to be made in the electro-negative element before 
water or hydrochloric acid can result. 
Just therefore in the same manner that so many elementary 
bodies can put on under the influence of external causes an ac- 
tive or passive condition, I infer, as the final result of the exper- 
iments brought forward in this memoir, that chlorine is one of 
these allotropic bodies, having a double form of existence. 'That, 
as commonly prepared, it is in its passive state; but that on ex- 
posure to the indigo rays, or other causes, it changes and assumes 
the active form. 'That, in this latter state, its affinity for hydro- 
gen becomes so great that it decomposes water without difficulty, 
as in the experiment which this memoir is designed to illustrate. 
On the relation of the preceding conclusions with the theory of 
substitutions. 
Having thus explained the facts which appear to indicate the 
allotropism of chlorine, I shal! now offer some considerations 
on its connection with the theory of substitutions of M. Dumas. 
Admitting the fact that the electro-negative qualities of chlo- 
rine are exalted upon its exposure to the indigo rays, and that 
