PART III. 



ORGANIC CHEMISTRY 



CHAPTER I. 



SECTION I. 



PRELIMINARY OBSERVATIONS. 



BY organic substances are meant definite chemical compounds, 

 found ready formed in organized beings, and their modifications 

 produced by artificial processes which may be greatly varied. 

 These substances are known to be definite in composition when 

 they are crystallizable, or when they enter into compounds that 

 are crystallizable ; or have, if liquid, a fixed boiling point. 

 In their number, which has been vastly increased by late re- 

 searches, are found many acids, several alkaline bodies, and a 

 large class of neutral substances which cannot be assimilated to 

 any class of inorganic compounds. Recent inquiries have 

 disclosed some unexpected relations between different organic 

 substances, and supplied the means of associating groups of 

 them from similarity of composition. There is the same evi- 

 dence of the existence in these substances of compound radicals, 

 which may be transferred from a state of combination with one 

 element to another, as in the compounds of the inorganic kingdom 

 allowed to contain such constituents \ although the organic radicals 

 cannot be isolated and exhibited in a separate state, except per- 

 haps in a single instance. The radicals most characteristic of 

 organic compounds, hitherto investigated, are of the basyle 

 class, bodies resembling therefore the metallic elements in their 

 functions and the series of compounds with salt radicals which 

 they are capable of forming. Of all these hypothetical radicals 

 ammonium has served as the prototype ; they are allowed how- 



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