PART II. 



THE CHEMICAL PROCESSES OF FERMENTATION, DECAY, 

 AND PUTREFACTION. 



CHAPTER I. 



Chemical Transformations. 



Woody fibre, sugar, gum, and all such organic compounds, 

 suffer certain changes when in contact with other bodies — that 

 is, they suffer decomposition. 



There are two distinct modes in which these decompositions 

 take place in organic chemistry. 



When a substance composed of two compound bodies, crystal- 

 lized oxalic acid for example, is brought in contact with concen- 

 trated sulphuric acid, a complete decomposition is effected upon 

 the application of a gentle heat. Now, crystallized oxalic acid 

 is a combination of water with the anhydrous acid ; but concen- 

 trated sulphuric acid possesses a much greater affinity for water 

 than oxalic acid, so that it attracts all the water of crystallization 

 from that substance. In consequence of this abstraction of the 

 water, anhydrous oxalic acid is set free ; but, as this acid cannot 

 exist in a free state, a division of its constituents necessarily 

 ensues, by which carbonic acid and carbonic oxide are produced, 

 and evolved in the gaseous form in equal volumes. In this 

 example, the decomposition is the consequence of the removal 

 of two constituents (the elements of water), which unite with 

 the sulphuric acid, and its cause in the superior affinity of the 

 acting body (the sulphuric acid) for water. In consequence of 

 the removal of the component parts of water, thf> remaining ele- 



