Familiar Letters on Chemistry | Page 5

different animals as manure.
LETTER XV
SOURCE OF THE CARBON AND NITROGEN OF PLANTS.
Produce of Carbon in Forests and Meadows supplied only with mineral
aliments prove it to be from the atmosphere. Relations between Mineral
constituents, and Carbon and Nitrogen. Effects of the Carbonic Acid
and Ammonia of Manures. Necessity of inorganic constituents to the
formation of aliments, of blood, and therefore of nutrition.
NECESSITY OF INQUIRIES by ANALYSIS to advance
AGRICULTURE.
LETTER XVI
RESULTS OF THE AUTHOR'S LATEST INQUIRIES. Superlative
importance of the PHOSPHATES OF LIME and ALKALIES to the
cultivation of the CEREALIA. Sources of a SUPPLY of these
MATERIALS.

LETTERS ON CHEMISTRY
LETTER I

My dear Sir,
The influence which the science of chemistry exercises upon human
industry, agriculture, and commerce; upon physiology, medicine, and
other sciences, is now so interesting a topic of conversation everywhere,
that it may be no unacceptable present to you if I trace in a few familiar
letters some of the relations it bears to these various sciences, and
exhibit for you its actual effect upon the present social condition of
mankind.
In speaking of the present state of chemistry, its rise and progress, I
shall need no apology if, as a preliminary step, I call your attention to
the implements which the chemist employs--the means which are
indispensable to his labours and to his success.
These consist, generally, of materials furnished to us by nature,
endowed with many most remarkable properties fitting them for our
purposes; if one of them is a production of art, yet its adaptation to the
use of mankind,--the qualities which render it available to us,--must be
referred to the same source as those derived immediately from nature.
Cork, Platinum, Glass, and Caoutchouc, are the substances to which I
allude, and which minister so essentially to modern chemical
investigations. Without them, indeed, we might have made some
progress, but it would have been slow; we might have accomplished
much, but it would have been far less than has been done with their aid.
Some persons, by the employment of expensive substances, might have
successfully pursued the science; but incalculably fewer minds would
have been engaged in its advancement. These materials have only been
duly appreciated and fully adopted within a very recent period. In the
time of Lavoisier, the rich alone could make chemical researches; the
necessary apparatus could only be procured at a very great expense.

And first, of Glass: every one is familiar with most of the properties of
this curious substance; its transparency, hardness, destitution of colour,
and stability under ordinary circumstances: to these obvious qualities
we may add those which especially adapt it to the use of the chemist,
namely, that it is unaffected by most acids or other fluids contained
within it. At certain temperatures it becomes more ductile and plastic
than wax, and may be made to assume in our hands, before the flame of
a common lamp, the form of every vessel we need to contain our
materials, and of every apparatus required to pursue our experiments.
Then, how admirable and valuable are the properties of Cork! How
little do men reflect upon the inestimable worth of so common a
substance! How few rightly esteem the importance of it to the progress
of science, and the moral advancement of mankind!--There is no
production of nature or art equally adapted to the purposes to which the
chemist applies it. Cork consists of a soft, highly elastic substance, as a
basis, having diffused throughout a matter with properties resembling
wax, tallow, and resin, yet dissimilar to all of these, and termed suberin.
This renders it perfectly impermeable to fluids, and, in a great measure,
even to gases. It is thus the fittest material we possess for closing our
bottles, and retaining their contents. By its means, and with the aid of
Caoutchouc, we connect our vessels and tubes of glass, and construct
the most complicated apparatus. We form joints and links of connexion,
adapt large apertures to small, and thus dispense altogether with the aid
of the brassfounder and the mechanist. Thus the implements of the
chemist are cheaply and easily procured, immediately adapted to any
purpose, and readily repaired or altered.
Again, in investigating the composition of solid bodies,--of
minerals,--we are under the necessity of bringing them into a liquid
state, either by solution or fusion. Now vessels of glass, of porcelain,
and of all non-metallic substances, are destroyed by the means we
employ for that purpose,--are acted upon by many acids, by alkalies
and the alkaline carbonates. Crucibles of gold and silver would melt at
high temperatures. But we have a combination of all the qualities we
can desire in Platinum. This metal was only first adapted to these uses
about fifty years since. It is cheaper than gold, harder