A SYSTEM

OF

THEORETICAL AND PRACTICAL

CHEMISTRY.

PART I.

SECT. I.

DEFINITION OF CHEMISTRY.

CHEMISTRY is that department of physical science the object of which is to investigate and account for the intimate changes produced in all bodies in nature by the mutual action of their parts upon each other; by means of which their physical properties are altered, and their individuality destroyed.

METHOD OF PERFORMING CHEMICAL

OPERATIONS.

In examining the changes which take place in natural bodies, chemistry employs either simple observation or operative experiment. It either observes the processes which are incessantly taking place in the great laboratory of nature, or institutes, on purpose for this or that investigation, new processes of its own.

When we observe how water is converted into ice, and ice into water; how metallic substances lose their lustre in

the open air; we then acquire chemical knowledge by simple observation. When, again, we kindle a fire, that we may see its action upon some combustible or incombustible body; when we immerse a solid into a fluid, that we may learn whether the solid will be dissolved or not, in consequence of the immersion; in these and other such cases we investigate chemical truth by experiments.

Of the chemical knowledge acquired by simple observation every man possesses more or less; and a very con siderable knowledge of the chemical changes of bodies may indeed be thus obtained. But mere unassisted observation is ever so inaccurate, so subject to accident, and so little capable of accomplishing any continuous and connected plan, that chemical inquiries almost always assume the form of experiment.

The artificial arrangement, or method which chemistry employs to favour the mutual action of bodies, consists in the proper application of those substances to each other which experience has taught us are best calculated to produce certain changes, that, in many cases, would otherwise be too minute to affect the senses individually.

Those operations themselves are called CHEMICAL PROCESSES, OPERATIONS, OR EXPERIMENTS.

GENERAL NATURE OF CHEMISTRY.

The processes of chemistry have been usually represented as either analytical or synthetical.

ANALYSIS, which is synonimous with decomposition, expresses the separation of the principles of a compound body. SYNTHESIS denotes the re-production of compound substances from simple bodies.

Analysis is divided into simple or perfect, and into complex or imperfect, analysis. It is called simple or perfect when, by means of synthesis, we can re-produce a body with the very substances which were the products of the analysis. It is complex or imperfect, when this cannot be effected. Simple analysis is the surest proof of the truth of chemical investigation: it is the most useful, and also the most rare, in all our artificial processes.

From this cursory account of the nature of the processes of chemistry, it becomes obvious that the whole art of the science consists in promoting the mutual actions of bodies

on each other, and carefully observing the phenomena that takes place. It must not be forgotten that these two methods do continually take place in the grand operations of nature, of which the chemist is only an imitator. The operations all depend on certain laws established between bodies, and require nothing more in order to their being rendered active than that the bodies should be placed into such situations as enable them to exercise their action. These important truths require to be maturely weighed and considered by the student who intends to embark in chemical pursuits.

Chemistry, therefore, consists in a detail of those facts which are founded on experiments and observations. Its basis is EXPERIENCE: from this, by regular conclusions, it deduces a THEORY, and connects a series of accurately established facts into a certain order, called a SYSTEM.

It follows from this that the evidence of chemical truth is, strictly speaking, only probable, not absolutely certain. This probability, however, is so much the greater as the experiments on which the observations are founded are more numerous, and have been more accurately performed. All possible exceptions, then, being made, we may venture to consider the results which offer themselves as true, till other facts are furnished, which by a more extensive and complete induction prove their fallacy.

It has been thus, by simple experiments and observation, that the science is become enriched with a store of facts. These facts have been gradually connected together, and arranged in such order as appeared most proper for exhibiting their reciprocal relation to each other; and at the same time for referring them to a smaller number of general heads, in order to consult them with the least difficulty, and to trace the laws that regulate them.

SECT. II.

SUBJECTS AND IMPORTANCE OF

CHEMISTRY.

CHEMISTRY, in its connexion with the operations of nature and the existence of man, is highly worthy of an accurate examination. It unfolds the causes of many important phenomena; it enables us to reason concerning those properties of bodies which most immediately concern us, and to predict their alterations; and it developes to us sublime views of the order and harmony belonging to the different parts of our system.

This branch of science has been slowly formed, in consequence of minute observations made upon natural events, and of experiments in which natural agents have been placed in new relations and though much has been done, much remains to be effected. The facts already ascertained are nevertheless sufficient to prove, that all the different known substances belonging to our globe are subjected to certain and invariable chemical laws, and that the most extensive and important chemical changes are continually taking place in the solid substance of the earth, the ocean, and in the atmosphere.

All material bodies are therefore the subjects of chemical research. The solid matters composing the terrestrial mass of the globe we inhabit; the aqueous fluids which penetrate its cavities, or float about its surface; the more subtile gazeous matter circumfused around it; the agencies of heat, light, and other imponderable substances expanded through space; are subjects for the chemical philosopher.

The events which chemistry holds out are equal to, and perhaps more important than, those which belong to mechanical philosophy. It extends itself into the province of active life. It is the nursing mother and guide of innumerable important arts. The arts of dyeing, bleaching, tanning, glass and porcelain-making, printing, the working of metals, &c. are purely chemical arts. They depend so much on that science, they are so combined

with its proper existence and its advancement, that all the steps which it makes in the knowledge of bodies, all the discoveries with which it is daily enriched, are so many new acquisitions for these arts; it perpetually improves them, adds to their processes, and creates new ones. Agriculture can only be rationally improved by calling in the assistance of the chemical philosopher; it is chemistry which explains the phenomena ogetation, germination, the growth, the ripening, and the death of plants.

To the PUBLIC ECONOMIST chemistry presents a treasure of useful information. By means of this science alone can he expect to attack with success the destroying pessilence, so far as it is an object of human prevention, and to guard against other evils to which the state of the elements give rise.

To the DOMESTIC ECONOMIST this science abounds with pleasing and wholesome lessons. It enables him to make a proper choice of meats and drinks; it directs him to those measures with respect to aliment, cookery, clothing, and respiration, which have the best tendency to promote health, enjoyment, and cheapness of living; and it sets him on his guard against unseen evils, to which those who are ignorant of its laws are continually exposed.

The GARDENER, whose employments are more curious than those of the farmer, equally needs its assistance. The nature of the different manures necessary for the various kinds of vegetables, the influence of light, the different temperatures, the quantity of moisture, the preservation of seeds, roots, plants, &c. are all founded upon chemical principles.

Chemistry likewise directs the labours of the HUSBANDMAN. In the DAIRY, milk cannot be kept sweet and fresh, butter cannot be made, cheese cannot be prepared, without a skill founded wholly upon chemical principles.

The CULINARY ART, for preparing wholesome and nutritious food; and the method of preserving bacon, hams, and other animal and vegetable substances, is entirely

chemical.

The whole PROCESS OF THE VINTAGE; the art of the brewer and distiller; the preparation of cyder, perry, home-made wines, &c. vinegar, &c. all depend upon chemical principles.