AGRICULTUU^ ^ CHEMISTRY. 



orilhant, in proportion to the increase of its 

 carbon, but we find, on the contrary, that it 

 burns like tinder, exactly as if no hydrogen 

 were present. For the purposes of fuel, 

 decayed or diseased wood is of little value, 

 for it does not possess the property of burn- 

 ing with flame, a property upon which the 

 advantages of common wood depend. The 

 hydrogen of decayed wood must conse- 

 quently be supposed to be in the state of 

 water; for had it any other form, the charac- 

 ters we have described would not be pos- 

 sessed by the decayed wood. 



If we suppose decay to proceed in a liquid, 

 which contains both carbon and hydrogen, 

 then a compound containing still more car- 

 bon must be formed, in a manner similar to 

 the production of the crystalline colourless 

 naphthalin from a gaseous compound of 

 carbon and hydrogen. And if the compound 

 thus formed were itself to undergo further 

 decay, the final result must be the separation 

 of carbon in a crystalline form. 



Science can point to no process capable 

 of accounting for the origin and formation 

 of diamonds, except the process of decay. 

 Diamonds cannot be produced by the action 

 of fire, for a high temperature, and the pre- 

 sence of oxygen gas, would call into play 

 their combustibility. But there is the greatest 

 reason to believe that they are formed in the 

 humid way, that is, in a liquid, and the pro- 

 cess of decay is the only cause to which their 

 formation can with probability be ascribed. 



Amber, fossil resin, and the acids in mel- 

 lite, are the products of vegetable matter 

 which has suffered decomposition. They 

 are found in wood or brown coal, and have 

 evidently proceeded from the decomposition 

 of substances which were contained in quite 

 a different form in the living plants-. They 

 are all distinguished by the proportionally 

 small quantity of hydrogen which they con- 

 tain. The acid from mellite (mellitic acid) 

 contains precisely the same proportions of 

 carbon and oxygen as that from amber (suc- 

 cinic acid ;) they differ only in the propor- 

 tion of their hydrogen. M. Bromeis* found 

 that succinic acid might be artificially formed 

 by the action of nitric acid on stearic acid, a 

 true process of eremacausis; the experiment 

 was made in this laboratory (Giessen.) 



CHAPTER XL 



VEGETABLE MOULD. 



THE term vegetable mould, in its general 

 signification, is applied to a mixture of dis- 

 integrated minerals, with the remains of 

 animal and vegetable substp'ices. It may 

 be considered as earth in which humus is 

 contained in a state of decomposition. Its 

 action upon the air has been fully investi- 

 gated by Ingenhouss and De Saussure. 



When moist vegetable mould is placed in 

 a vessel full of air, it extracts the oxygen 



* Lie-big's Annalen, Band xxxiv., Heft 3.. 



therefrom with greater rapidity than decayed 

 wood, and replaces it by an equal volume of 

 carbonic acid. When this carbonic acid is 

 removed and fresh air admitted, the same 

 action is repeated. 



Cold water dissolves only 1( y^ 00 th of its 

 own weight of vegetable mould; and the 

 residue left on its evaporation consists of 

 common salt with traces of sulphate of pot- 

 ash and lime, and a minute quantity of "or- 

 ganic matter, for it is blackened when heated 

 to redness. Boiling water extracts several 

 substances from vegetable mould, and ac- 

 quires a yellow or yellowish brown colour, 

 which is dissipated by absorption of oxygen 

 from the air, a black flocculent deposit being 

 formed. When the coloured solution is 

 evaporated, a residue is left which becomes 

 black on being heated to redness, and after- 

 wards yields carbonate of potash when 

 treated with water. 



A solution of caustic potash becomes 

 black when placed in contact with vegetable 

 mould, and the addition of acetic acid to the 

 coloured solution causes no precipitate or 

 turbidity. But dilute sulphuric acid throws 

 down a light flocculent precipitate of a 

 brown or black colour, from which the acid 

 can be removed wit difficulty by means of 

 water. When this precipitate, after having 

 been washed with water, is brought whilst 

 still moist under a receiver filled with oxy- 

 gen, the gas is absorbed with great rapidity ; 

 and the same thing takes place when the 

 precipitate is dried in the air. In the per- 

 fectly dry state it has entnely lost its solu- 

 bility in water, and even alkalies dissolve 

 only traces of it. 



It is evident, therefore, that boiling water 

 extracts a matter from vegetable mould, 

 which owes its solubility to the presence of 

 the alkaline salts contained in the remains 

 of plants. This substance is a product 01 

 the incomplete decay of woody fibre. Its 

 composition is intermediate between woody 

 fibre and humus, into which it is converted, 

 by being exposed in a moist condition to 

 the action of vhe air. 



CHAPTER XII. 



ON THE MOULDERING OF BODIES. PAPER, 



BROWN COAL, AND MINERAL COAL. 



THE decomposition of wood, woody fibre, 

 and all vegetable bodies when subjected to 

 the action of water, and excluded from the 

 air, is termed mouldering. 



Wood, or brown coal and mineral coal, 

 are the remains of vegetables of a former 

 world; their appearance and characters 

 show, that they are products of the pro- 

 cesses of decomposition termed decay and 

 putrefaction. We can easily ascertain by 

 analysis the manner in whicn their consti- 

 tuents have been changed, if we suppose 

 the greater part of their bulk to have been 

 formed from woody fibre, 

 i But it is necessary, before we can obtain 



