354 
SCIENCE OF CHEMISTRY DISPLAYED. 
nical separation is any longer practicable; the 
particles are so minute as to elude all search. 
Yet ‘this does not hinder us from regarding 
such a compound as still a mere mixture, and 
its properties are accordingly intermediate 
between those of the liquids mixed. But this 
is far from being the case with all liquids. 
When a solution of potash, for example, and 
another of tartaric acid, each perfectly liquid, 
are mixed together in proper proportions, a 
great quantity of solid saline substance falls 
to the bottom of the containing vessel, 
which is quite different from potash or tar- 
taric acid, and the liquid from which it sub- 
sided offers no indications by its taste, or 
other sensible qualities, of the ingredients 
mixed, but of something totally different from 
either. It is evident that this is a phenonae- 
non widely different from that of mere mix- 
ture : there has taken place agreatand radical 
change in the intimate nature of the ingre- 
dients, by which anew substance is produced 
which had no existence before ; and it has 
been produced by the union of the ingre- 
dients presented to each other, for, when 
examined, it is found that nothing has been 
lost, the weight of the whole mixture being 
the sum of the weights mixed. _ Yet the 
potash and tartaric acid have disappeared 
entirely, and the weight of the new product 
is found to be exactly equal to that of the 
tartaric acid and potash employed, taken 
together, abating a small portion held in so- 
lution in the liquid, which may be obtained, 
however, by evaporation. They have, there- 
fore, combined, and adhere to one another 
with a cohesive force sufficient to form a 
solid out of a liquid ; a force which has been 
called into action by merely presenting them 
to each other in a state of solution.”'*' 
As it is the object of Chemistry to deter- 
mine the composition of different substances, 
therefore, if we could reduce all bodies to 
their elementary principles, and discover 
the proportions in which these principles 
must be combined in order to recompose such 
bodies, the science of Chemistry would be 
complete. This, however, is far from being 
the case, notwithstanding the extraordinai-y 
discoveries that have rewarded the labours of 
those philosophers who have paid attention 
to this important branch of knowledge. But 
though we allow that much remains to be 
achieved by future experimentalists ere Che- 
mistry can be said to make any near approach- 
es to perfection, yet it must be admitted, that 
the improvements which have taken place 
in this science in our own times are of no 
common importance, since its first principles 
have been fixed on the firm basis of experi- 
ment, and a luminous system, founded on 
facts, has superseded those obscure and hy- 
pothetical speculations which occur in the 
writings of the older chemical authors. 
Among the most important discoveries of 
modern philosophers, we may reckon those 
which relate to that inherent tendency wrhich 
matter possesses to form new combinations. 
* Herschel’g Discourse on the Study of Na- 
tural Philosophy, pp. 298, 
This property of matter gives rise to many 
of those operations of nature which we view 
■without surprise, only because they are com- 
mon ; and it is not less concerned in seve- 
ral of the most striking and extraordinary 
phenomena of nature and art. Thus, when 
we procure light or heat by burning any 
combustible substance, as, for instance, wood, 
chemical action takes place between the 
inflammable matter contained in the wood, 
and part of the air of the room in which the 
wood is burned ; in consequence of which, a 
new kind of air is formed, the greater part of 
which flies off with the smoke. The respira- 
tion of animals affords another instance of 
chemical action. When air is taken into the 
lungs, a part of it combines with something 
which separates from the blood ; in conse- 
quence of which combination, the air becomes 
altered in its properties, as must be obvious 
to every one who considers that the atmos- 
phere of a crowded apartment, not properly 
ventilated, is soon rendered so noxious as to 
occasion considerable inconvenience, and even 
faintness, to those whose constitutions are 
delicate. 
On taking a survey - of the various bodies 
around us, -we may observe that some among 
them, which we reckon inert, because from 
the influence of habit, or other causes, they 
make but a slight impression on our senses, 
are yet endowed with active powers or pro- 
perties, which render them capable of pro- 
ducing remarkable changes in other bodies. 
Thus, water, which is insipid to the tongue, 
and which, in its operation on living animals 
and vegetables, acts slowly and almost im- 
perceptibly, will yet, if placed in contact with 
a lump of salt or sugar, speedily reduce 
either from the solid to the liquid state. 
Atmospheric air, though it is necessary for 
the support of animal and vegetable existence, 
and gives rise to scarely any sensations but 
such as depend on variations of temperature, 
yet this widely extended gaseous body, by 
its union with other substances, sometimes 
produces the most striking phenomena. 
Thus, the explosion of fire-damp in coal-mines 
can only happen when the inflammable gas, 
so called, is mixed with a certain portion of 
common air. 
One of the most obvious modes of distin- 
guishing bodies is that which depends on 
their different degrees of density ; whence the 
arrangement of substances into the respec- 
tive classes called solids, liquids, and gases, 
already noticed. But these distinctions can- 
not be advantageously employed as the basis 
of a chemical classification of natural bodies, 
for reasons which have been already stated. 
Hence, some other mode of discrimination 
and arrangement becomes requisite, and 
such a one may be most properly derived 
from considering the chemical relations of 
different kinds of matter, and the products 
derived from their action on each other. 
There are some bodies which, by no known 
mode of treatment without addition, can be 
made to form more than one species of mat- 
ter ; for, however they may be divided, or 
subdivided, each particle still possesses the 
