11 
DECOMPOSITION OR PUTREFACTION OF VEGETABLES. 
The following extract is taken from Hugh Reid's " Chemistry of Nature" 
lately published, a little work of great merit, calculated to be extremely useful, not 
only merely to those who desire to acquire some knowledge of the chemistry of 
natural objects, but also to those who have not the means or opportunity of pro- 
secuting chemical experiments, and as well, highly edifying to the general reader ; 
" containing upwards of 300 pages." 
" All vegetables, when the principle of life has departed from them, begin 
spontaneously to be decomposed (to putrefy). The elements which enter into the 
composition of plants, when left entirely to the disposal of their chemical affinities, 
have a tendency to separate from each other, and form new compounds, very dif- 
ferent from those which compose the living plant. This is termed the *' spontane- 
ous decomposition" of vegetables. The substances formed by the new arrange- 
ment of the elements of the veojetable are aerial and colourless ; — hence the 
entire disappearance of the vegetable, as if it had been totally annihilated when 
life ceased to preserve its particles together in the vegetable form. 
" The compounds formed, when the vegetable dies and putrefaction goes on, 
are, carbonic acid, water, carbonic oxide, and carburetted hydrogen. The two 
former are the chief results of the decomposition ; the two latter are formed more 
sparingly, and principally when there is not a free supply of oxygen to the 
substance undergoing decomposition. The carbon and hydrogen of the plant have 
a constant tendency to unite with oxygen, and form carbonic acid and water. 
Now there is never present in the vegetable a sufficient quantity of oxygen to 
convert all the carbon into carbonic acid, and all the hydrogen into water ; hence, 
if there be not a sufficient supply of oxygen to produce these compounds presented 
from external sources, as from the air, the two other matters are formed, one of 
which (carbonic oxide) requires a less quantity of carbon than the carbonic acid, 
while the other (carburetted hydrogen) requires no oxygen, consisting of carbon 
and hydrogen." 
" In vegetables which decay under water, carburetted hydrogen is abundantly 
formed ; hence arises the gas which is found so plentifully in summer in stagnant 
waters containing quantities of putrefying vegetables." 
" The spontaneous decomposition of vegetables goes on most rapidly when they 
are exposed to the air, kept moist, and preserved at a degree of warmth higher 
than the usual temperature of the atmosphere. Putrefaction is retarded or almost 
prevented if the vegetable be dried, so that its own moisture is expelled, carefully 
excluded from air and moisture, and kept cold. The influence of heat in pro- 
moting the decay of vegetables depends upon the repulsive power it possesses, by 
which it disposes the various elements to assume the gaseous form. Animals and 
vegetables are frequently found in snow or ice, in a high state of preservation." 
