and the Oxidability of certain substances upon common Oxygen. 25 



with light is^ to exalt the chemical affinities of free common 

 oxygen to such an extent as to render that element capable of 

 destroying indigo just as well as ozone does. I have reason to 

 believe that indigo is not the only organic substance which is 

 indirectly oxidized by sulphurous acid^ for I have succeeded in 

 destroying some very strongly coloured organic matters by the 

 joint agency of light, sulphurous acid and common oxygen. 



It is worthy of remark, that the amount of the exalting effects 

 produced by light conjointly with sulphurous or tartaric acids, 

 &c. upon oxygen far surpasses the sum of the effects brought 

 about singly by those agents. Insolated oxygen or air of itself 

 certainly is capable of discharging the colour of indigo solution, 

 and so is oxygen placed under the exciting influence of sulphu- 

 rous acid, tartaric acid> &c. unassisted by light ; but in both cases 

 the action is very slow, whilst it is rapid if both causes be work- 

 ing together. The facts, that linseed oil, on being shaken with 

 copper filings and atmospheric air in sunlight, soon turns green, 

 brass in contact with fatty matters assumes the same colour, 

 mercury contained in a divided state in the unguentum mercu- 

 riale is gradually transformed into the protoxide, fibrous mat- 

 ters impregnated with oils are now and then spontaneously set 

 on fire, &c., seem to be connected with the exciting influence 

 exerted by oxidable matters upon ordinary oxygen. 



If, according to Berzelius and others, ozone be but an allo- 

 tropic modification of common oxygen, we must admit that phos- 

 phorus, like electricity, has the power of causing that extraordi- 

 nary change of condition in common oxygen, and are led to sup- 

 pose that phosphorus stands not alone in this respect. Indeed, 

 my late researches on oil of turpentine, &c. show that many other 

 substances make oxygen act (even independently of light) as 

 phosphorus does. 



Now these facts seem to give room to the conjecture, that 

 many oxidable matters and oxygen, on being put in contact with 

 one another, exert a peculiar influence upon each other previous 

 to their chemically uniting with one another. As to phosphorus, 

 oil of turpentine, &c., it seems as if the first action produced 

 upon common oxygen be the allotropification of that body, and 

 the oxidation of phosphorus the sequel, and not the cause of the 

 formation of ozone. I therefore think it not impossible, that at 

 least some of those strange chemical phsenomena, called cata- 

 lytic, may be connected with an action similar to that pro- 

 duced by phosphorus, oil of turpentine, &c. upon oxygen, i. e. 

 depend upon allotropic modifications of elementary bodies brought 

 about by the mere contact of certain substances. Certainly we 

 do not know as yet in what the allotropic modifications consist, 

 and how they are effected ; but whatever they may depend upon 



