THE OllGANIC ELEMENTS. 29 



and still holds by Schulze's opinion, either cannot or will not see. I can 

 confirm all that Berzelius has said on this subject in his Chemistry.* 



7. Humus (Humin, Humic Acid, Ulmin, Ulmic Acid, &c.). If dead 

 animal and vegetable matters are exposed to the action of moisture and 

 the atmosphere, oxygen from the air is absorbed ; the nitrogen unites 

 with hydrogen to form ammonia, which, either alone or in combina- 

 tion with carbonic acid formed at the same time, disappears if it be not 

 fixed by some acid previously present or formed at the same time. The 

 carbon forms carbonic acid ; the hydrogen, combining with the oxy- 

 gen of the air, forms water, and with its nitrogen, if the decompo- 

 sition takes place in a closed vessel, or as it does in the soil, forms am- 

 monia ; at last nothing remains but the inorganic salts of the plant 

 or animal. Between these changes, however, a number of other sub - 

 stances occur. The indifferent, insoluble, richly carbonaceous mass, 

 when it is black, is called Humin ; when brown, Ulmin. Further, 

 from these five acids present themselves, humic, ulmic, geinic, crenic, 

 and apocrenic acids. They were long regarded as substances between 

 resin and wax, and can be obtained in considerable quantities from 

 vegetable mould composed of leaves six years old, by washing with 

 ether. The acids combine with the alkalies, and even with the earths, 

 and form soluble salts which constitute the so-called humus-extract. 

 The mixture of these substances, combined with portions of the rocks 

 which form the surface of the earth, constitute the arable land or cul- 

 tivable soil, and which is the natural and most promising medium of 

 growth for the greater proportion of plants. The first-formed in time is 

 the ulmic acid, which consists of C 40 H 14 O 12. This, through ab- 

 sorption of 2 O, and the separation of 2 H O, is converted into humic 

 acid, C 40 H 12 O 12 ; and this, through the absorption of 91 O, and the 

 separation of 40 CO 2 and 24 H O, is changed into geinic acid, C 40 

 H 12 O 14. These three acids are almost insoluble in water, and are 

 precipitated by strong acids from alkaline humus-extract. There re- 

 mains in the solution crenic acid (C 24 H 12 O 16), and apocrenic acid 

 (C 48 II 12 24) : the last through acetate of copper, and the first 

 through acetate of copper and carbonate of ammonia, are precipitated as 

 crenate and apocrenate of copper. The following may be taken as an 

 example of the formation of these substances : 



C H O N 

 7 Eq. of Cellulose + 80 = 84 70 78 



2 Eq. Humin . . = 80 24 24 



4 Carbonic acid 4 80 

 46 Water . = 46 46 



84 70 78 

 1 Eq. Protein -f 4 Eq. O. = 40 31 16 10 



1 Eq. Humin . . =40 15 15 



1 Water . 0110 



5 Ammonia . 15 10 



40 31 16 10 



For further information on these substances, the reader may consult 

 Mulder, Bulletin des Sciences Phys. et Nat. en Neerlande Annee, 1840, 

 liv. i., and Physiological Chemistry. 



* Gutta Fercha belongs to this group of vegetable products. TKANS. 



