FORMATION OF CARBONIC \CID. 



f of the oxygen absorbed have not united with the carbon. It is 

 highly probable, that during the oxidation of the hydrogen, a 

 portion of the carbon had united with the oxygen contained in the 

 hsematin, and had separated from the other elements as carbonic 

 acid. 



The experiments of De Saussure upon the decay of woody 

 fibre show that such a separation is highly probable. Moist 

 woody fibre evolved one volume of carbonic acid for every 

 volume of oxygen which it absorbed. It has just been mentioned 

 that carbonic acid contains its own volume of oxygen. Now, 

 woody fibre contains carbon and the elements of water, so that 

 the result of the action of oxygen upon it is exactly the same, 

 as if pure charcoal had combined directly with oxygen. But 

 the characters of woody fibre show, that the elements of water 

 are not contained in it in the form of water ; for, were this the 

 case, starch, sugar, and gum must also be considered as hydrates 

 of carbon. 



But if the hydrogen does not exist in woody fibre in the form 

 of water, the direct oxidation of the carbon cannot be considered 

 as at all probable, without rejecting all the facts established by 

 experiment regarding the process of combustion at low tempera- 

 tures. 



If we examine the action of oxygen upon a substance con- 

 taining a large quantity of hydrogen,. such as alcohol, we find 

 most distinctly, that the direct formation of carbonic acid is the 

 last stage of its oxidation, and that it. is preceded by a series of 

 changes, the last of which is a complete combustion of the hy- 

 drogen. Aldehyde, acetic, formic, oxalic, and carbonic acids, 

 form a connected chain of products arising from the oxidation of 

 alcohol : and the successive changes which this fluid experi- 

 ences from the action of oxygen may be readily traced in them. 

 Aldehyde is alcohol minus hydrogen ; acetic acid is formed by 

 the direct union of aldehyde with oxygen. Formic acid and 

 water are formed by the union of acetic acid with oxygen. 

 When all the hydrogen is removed from formic acid, oxalic acid 

 is produced ; and the latter acid is converted into carbonic acid 

 by uniting with an additional portion of oxygen. All these pro- 

 ducts appear to be formed simultaneously, by the action of oxid- 



