COMPOSITION OF HUMUS. 31 



humus, and humin, are names applied to modifica- 

 tions of humus. They are obtained by treating peat, 

 woody fibre, soot, 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 modifications of humus which are soluble in 

 alkalies, are called humic acid ; while those which 

 are insoluble have received the designations oi humin 

 and coal of humus* 



The names given to these substances might cause 

 it to be supposed that their composition is identical. 

 But a more erroneous notion could not be enter- 

 tained ; since even sugar, acetic acid, and resin do 

 not differ more widely in the proportions of their 

 constituent elements, than do the various modifica- 

 tions of humus. 



Humic acid formed by the action of hydrate f of 



* The soluble matters were formerly called by the eminent Swedish 

 chemist Berzelius, extract of humus^ and the insoluble geine (from the 

 Greek yyj^ the earth), also apotheme and carbonaceous humus. This 

 substance is now known to be composed of various ingredients, and of 

 these the two acids, which have received the names of Crenic and 

 ^pocrenic, are particularly interesting. 



See Professor Hitchcock's Report, and American Journal of Science, 

 Vol. XXXVL, Art. XII. 



Dr. S. L. Dana considers geine as forming the basis of all the nour- 

 ishing part of all vegetable manures, and, in the three states of" vegeta- 

 ble extract, geine, and carbonaceous mould," to be the principle which 

 gives fertility to soils long after the action of common manures has 

 ceased. See Report on the reexamination of the Economical Geology 

 of Massachusetts. In the Third Report on the Agriculture of the State 

 of Massachusetts, 1840, Dr. Dana remarks, that geine "is the decom- 

 posed organic matter of the soil. It is the product of putrefaction ; 

 continually subjected to air and moisture, it is finally wholly dissipated 

 in air, leaving only the inorffanic bases of the plant, with which it was 

 once combined. Now, whetner we consider this as a simple substance, 

 or composed of several others, called crenic, apocrenic, puteanic, ulmic 

 acids, glairin, apotheme, extract, humus, or mould, agriculture ever 

 has and probably ever will consider it one and the same thing, requir- 

 ing always similar treatment to produce it; similar treatment to render 

 it soluble when produced; similar treatment to render it an effectual 

 manure. It is the end of all compost heaps to produce soluble geine, 

 no matter how compound our chemistry may teach this substance to 

 be." Page 191. 



f Hydrates are compounds of oxides, salts, &c., with definite quan- 

 tities of water, — a substance from wlych all the water has been re- 

 moved is anhydrous. Even after exposure to a red heat, caustic potash 

 retains water. 



