TRANSFORMATIONS OF ORGANIC SUBSTANCES. 69 



Temperature, Light, Galvanism, or any other influ- 

 ence, the act of transformation is a purely chemical 

 process. Combination and Decomposition can take 

 place only when the elements are disposed to these 

 changes. That which chemists name affinity indi- 

 cates only the degree in which they possess this 

 disposition. It will be shown, when considering the 

 processes of fermentation and putrefaction, that every 

 disturbance of the mutual attraction subsisting be- 

 tween the elements of a body gives rise to a trans- 

 formation. The elements arrange themselves accord- 

 ing to the degrees of their reciprocal attraction into 

 new combinations, which are incapable of further 

 change under the same conditions. 



The products of these transformations vary with 

 their causes, that is, with the different conditions on 

 which their production depended ; and are as innu- 

 merable as these conditions themselves. The chem- 

 ical character of an acid, for example, is its unceas- 

 ing disposition to saturation by means of abase;* 

 this disposition differs in intensity in different acids ; 

 but when it is satisfied, the acid character entirely 

 disappears. The chemical character of a base is 

 exactly the reverse of this, but both an acid and a 

 base, notwithstanding the great difference in their 



* Liebig applies the term base to compounds which unite with acids 

 and neutralize their characters. The product is a salt. When the 

 characters of both acids and bases disappear the compound is neutral. 



Some acids contain oxygen, others hydrogen. Several metals form 

 acids with oxygen ; but the greater number of metallic oxides, are, in 

 their relations, totally different from the acids. They form conipounds, 

 which, for the most part, are insoluble in water ; those soluble in water 

 have an alkaline taste, and possess the property of restoring the blue 

 color of vegetables, which have been reddened by acids. These also 

 change many vegetable yellows to red or brown. The alkalies are 

 soluble bases. Many salts redden vegetable blues, and others again 

 restore the blue color of vegetables reddened by acids ; in the first 

 instance, the salt possesses an acid, and in the latter an alkaline, 

 reaction. 



A simple body, which is capable of forming either an acid or a base, 

 is termed a radical; a compound radical consists of two or three simple 

 radicals, and comports itself in a similar manner to the simple radicals; 

 that is, it is capable of forming acids and bases. 



