264 EREMACAUSIS OR DECAY. 



and forms water, which remains in union with the 

 anhydrous benzoic acid. 



According to the experiments of Dobereiner, 160 

 parts of pyrogallic acid absorb 38*09 parts of oxygen 

 when in contact with ammonia and water ; the 

 acid being changed in consequence of this absorp- 

 tion into a mouldy substance, which contains less 

 oxygen than the acid itself. It is evident that the 

 substance which is formed is not a higher oxide ; 

 and it is found, on comparing the quantity of the 

 oxygen absorbed with that of 'the hydrogen con- 

 tained in the acid, that they are exactly in the pro- 

 portions for forming water. 



When colourless orcin is exposed together with 

 ammonia to the contact of oxygen gas, the beauti- 

 ful red- coloured orcein is produced. Now, the 

 only changes which take place here are, that the 

 absorption of oxygen by the elements of orcin and 

 ammonia causes the formation of water ; 1 equiva- 

 lent of orcin CIS H12 O8, and I equivalent of 

 ammonia, NH3 absorb 5 equivalents of oxygen, and 

 5 equivalents of water are produced, the composition 

 of orcein being CIS H 10 O8 N. (Dumas.) In this 

 case it is evident, that the oxygen absorbed has 

 united merely with the hydrogen. 



But, although it appears very probable that the 

 oxygen acts primarily and principally upon hydro- 

 gen, the most combustible constituent of organic 

 matter in the state of decay ; still it cannot thence 



