AGRICULTUKAL CHEMISTRY. 141 



formed. The fact that hydrogen is more susceptible of oxydation than 

 carbon, to a certain extent explains the production of these bodies. 



In the decay of sugar under the action of ferments there appears 

 in an analogous manner a series of intermediate bodies, which differ 

 in character according to the circumstances under which the fermen- 

 tation is conducted. 



The intermediate products of the decay of vegetable matters, wood, 

 &c, accumulate in large masses, especially where submersion in water 

 cuts off the free access of oxygen and keeps the temperature reduced. 

 In this way the peat of swamps and bogs is formed, and the immense 

 coal beds now buried in the rock strata of the earth are doubtless 

 nothing but the peat of a former geological epoch altered in its 

 character by further chemical agencies. 



The final products of complete decay are universally the same, 

 whatever may be the intervening stages. The carbon of organic 

 bodies is oxydized to carbonic acid. The hydrogen is mainly converted 

 into water. Nitrogen unites more or less with hydrogen, forming am- 

 monia: in part, however, it escapes in the free state. Sulphur and phos- 

 phorus arc converted into sulphuric and phosphoric acids. The fixed 

 mineral matters remain. 



Combustion, or burning, is likewise a process of oxydation. It 

 differs from decay in the rapidity with which it occurs, and in the 

 different intermediate products that result; but otherwise it is the 

 same, its final issues being identical with those of decay. Combus- 

 tion may, in fact, be called a quick decay, as decay has been termed 

 by Liebig, a slow burning — ercmecausis. It is easy to illustrate, by 

 simple experiments, the formation of water, carbonic acid, and am- 

 monia in the burning of organic substances. 



When burning non-nitrogenous bodies, as the wax and cotton of a 

 lighted taper, are looked upon, under ordinary circumstances, we 

 gain the impression, indeed, that the) r themselves waste away, but 

 we perceive no result of the fire except light and heat. If, how- 

 ever, an inverted dry glass bottle be lowered over the flame, and 

 held so for a time, a mist presently gathers on its interior walls, and 

 after a little drops of a liquid may be collected which are pure water. 

 The bottle still being kept in the same position, we shortly see the 

 flame becoming smaller, and its light dimmer, making it evident that 

 something in the air which feeds the flame is being exhausted from 

 the limited space that surrounds it. If, now, the bottle be removed, 

 and have a little clear lime-water agitated in it. there will at once be 

 formed a copious precipitate, as the chemist technically designates it, 

 of carbonate of lime, the lime-water having served to make the in- 

 visible carbonic acid that resulted from the union of atmospheric 

 oxygen with the carbon of the Avax, evident to the sense of sight. 



During the combustion of a nitrogenous body, in addition to water and 

 carbonic acid, we may detect ammonia. Thus, if the smoke of a cigar be 

 puffed against moist turmeric paper, (paper saturated with the yellow 

 coloring principle of the turmeric or curcuma root, which is turned 

 brown by alkalies,) the change of color at once shows the presence of 

 ammonia. This body is always found in the soot of chimneys, where 



