334 EXPERIMENTAL INVESTIGATIONS. 



thermic molecular repulsion, and regard chemical affinity as 

 being antagonised by physical repulsion. 



Pursuing the series of analogies from the decomposition of 

 euchlorine at a low temperature, that of ammonia at a higher, 

 that of metallic oxides at a higher, and so on to oxide of 

 hydrogen, there appears to be an extensive series of facts 

 which afford strong hope of a generalised antagonism be- 

 tween thermic repulsion and chemical affinity, and a con- 

 sequent establishment of the law of continuity in reference to 

 physical and chemical attraction. 



The deposit from chlorine, to which I have alluded in my 

 paper, I have since examined, and though it differs in colour 

 from that described in books, I find it is a protochloride of 

 platinum, formed at the expense of the platinum wire. The 

 larger portion of the chlorine in the tube combines with the 

 hydrogen of the aqueous vapour, and the muriatic acid is 

 absorbed by the water ; when the experiment terminates the 

 gaseous volume is reduced to nearly one-half, and this residue 

 is oxygen; 



This effect induced me to try an ignited wire on other 

 analogues of chlorine, and I tried bromine and chloride of 

 iodine in the apparatus (fig. 5). The tube was filled with the 

 liquid, and its extremity was in the first experiments im- 

 mersed in another narrow tube of the same liquid as that 

 which filled it. When the platinum wire was ignited perma- 

 nent gas was given off, both from the bromine and from the 

 chloride of iodine, which gas on examination proved, to my 

 surprise, to be oxygen. In one experiment I collected half a 

 cubic inch of gas from an equal volume of chloride of iodine. 

 As the experiment in this form required too large a quantity 

 of the liquid to enable me to observe any change which might 

 take place in its character, I repeated it with a tube five feet 

 long, bent in two angular curves. A small quantity of the 

 liquid was placed in the extremity of the tube containing the 

 wire, which was so arranged as to be the lowest point ; the 

 angles were placed in cold water and the experiment pro- 

 ceeded with ; my object was to enable the dense vapour of 

 the liquids to shelter them from the atmosphere, there being 

 no satisfactory method of shutting them in and yet allowing 



