SOURCE OF THE CARBON. 139 



nite compound as soluble gcine, but makes the substance so 

 called consist of crcnic and apocrenic acids, combined in part, 

 with bases forming in fact a mass of salts. 



Liebig disregards all these different substances, and calls 

 the whole humus or humic acid. This geine or humic acid 

 of soils, appears to be identical in composition with a sub- 

 stance, noticed by Vauquelin in the bark of the elm, and 

 which is the product of vitality called ulmin, and ulmic acid. 

 It is in fact, elm-gum, or mucillage. It was also called humic 

 acid. But Berzelius regards the ulmic or humic acid of soils, 

 which is the product of decay or death, as different from that 

 which is the product of life. There are also several artificial 

 compounds, which are nearly identical with humic acid. 

 " Ulmin, humic acid, coal of humus and humin,^^ says Liebig, 

 " are names applied to different modifications of humus. 

 They are obtained by treating peat, woody fibre, or brown 

 coal with alkalies ; by decomposing sugar, starch, or sugar of 

 milk by means of acids ; or by exposing alkaline solutions of 

 tannic and gallic acids to the action of the air." The soluble 

 parts he calls huinic acid; and the insoluble, humin or coal 

 of humus. Liebig has attempted to show, that these artifi- 

 cial products, although they have received the same name, 

 humic acid, are as different in composition, as sugar, acetic 

 acid and resin ;* and that there is not the slightest ground 

 for the belief, that any one of them "exists in nature in the 

 form, and endowed with the properties, of the vegetable con- 



* Thus the sulphate of potash and saw-dust, when fused form hu- 

 mic acid containing 72 parts of C in 100 (Peligot). Turf and brown 

 coal yield an acid containing 58 parts of C in 100 (Sprengel). Di- 

 lute sulphuric acid and sugar yield 57 parts of C (Malaguti). Muriat- 

 ic acid and sugar or starch yield 64 per cent, of C (Stein). Malaguti 

 states, that humic acid contains an equal number of equivalents of oxy- 

 gen and hydrogen ; but according to Sprengel, the oxygen is in ex- 

 cess, and Peligot estimates the excess to be 14 equiv. of oxygen to 

 6 of hydrogen ; but, Hermann makes the humic acid of soils to be 

 composed of 58 parts of C, 2.10 of hydrogen, and 39.90 of oxygen. 



