On the Connexion of Catalytic Phenomena with AUotropy. 441 



exposed to heat than ia the cold^ ^ as follows from, the fact that 

 oil of turpentine quite free from O, spread out in a thin layer and 

 exposed in summer to the air and light, dries up to resin in far 

 shorter time than is the case under the same circumstances in 

 winter. This formation of resin, like the oxidation of sulphurous 

 to sulphui'ic acid, or of indigo-blue to isatine, is not effected by 

 0, but by 0. 



If the allotropy of oxygen had not been discovered, and if the 

 allotropizing property of oil of turpentine wei'e still unknown, the 

 fact, that this gas, standing in contact with oil of turpentine, 

 oxidizes a series of substances towards which it is of itself che- 

 mically indifferent, would be considered as a contact or catalytic 

 action of the oil. We may now, however, go a step further, and 

 may refer the oxidizing actions caused by the oil of turpentine, 

 like so many other so-called catalytic actions, to an allotropic 

 modification of oxygen, produced in this case by the oil of tur- 

 pentine. 



The comportment, not only of the rest of the camphene oils 

 and of common aether, but also of several other organic sub- 

 stances, is similar to that of oil of turpentine. One of the most 

 interesting of these is contained in the juice of many mushrooms, 

 and I showed, last year, that it takes up common oxygen even 

 in the dark, and so changes it that it may be readily transferred 

 to other oxidizable substances; a substance, therefore, which 

 again is comparable to binoxide of nitrogen as aa exciter of 

 oxygen and carrier of 0. 



Substances quite analogous, as far as this chemical action is 

 concerned, are found in a large number of plants, and pro- 

 bably occur more or less extensively in all. I have found them 

 in the most various species of plants ; and I will here add, that 

 the wide diffusion of such organic ozonizing substances may be 

 very easily proved by means of freshly-prepared tincture of gua- 

 iacum. Every substance by which this resin-solution is turned 

 blue has the property of transforming into O ; and everything 

 which causes this coloration, even without the presence of 0, is 

 to be considered as a carrier of 0. 



Indigo-blue dissolved in sulphuric acid is another very valu- 

 able means of recognizing the various conditions of oxygen, and 

 may be applied for this purpose in many cases in which the 

 tincture of guaiacum could not be iised. Since this colouring 

 matter can be oxidized to isatine by O, but not by 0, it can be 

 conjectured from the decolorization, or from the uuchangeability 

 of the indigo solution, whether under the given circumstances O 

 has been changed into or not. 



I have already shown, years ago, that tincture of indigo is 

 decomposed by common oxygen, when both bodies are placed 



Phil. May. S. 4. Vol. 13. No. 88. June 1857, 2 II 



