POPULAR CHEMISTRY. INTRODUCTORY. Why is the science of chemistry so named? Because of its origin from the Arabic, in which language it signifies "the knowledge of the composition of bodies.' The following definitions of chemistry have been given by some of our best writers : 66 Chemistry is the study of the effects of heat and mixture, with the view of discovering their general and subordinate laws, and of improving the useful arts."-Dr. Black. 'Chemistry is that science which examines the constituent parts of bodies, with reference to their nature, proportions, and method of combination."-Bergman. Chemistry is that science which treats of those events or changes, in natural bodies, which are not accompanied by sensible motions."-Dr. Thompson. "Chemistry is a science by which we become acquainted with the intimate and reciprocal action of all the bodies in nature upon each other."-Fourcroy. The four preceding definitions are quoted by Mr. Parkes, in his Chemical Catechism. Dr. Johnson (from Arbuthnot) defines "chymistry” as "philosophy by fire." Mr. Brande says It is the object of chemistry to investigate all changes in the constitution of matter, whether effected by heat, mixture, or other means.”Manual, 3rd edit. 1830. Dr. Ure says" Chemistry may be defined the science which investigates the composition of material substances, and the permanent changes of constitution which their mutual actions produce." - Dictionary, edit. 1830. Sir Humphry Davy, in his posthumous work,* says, "There is nothing more difficult than a good definition of chemistry; for it is scarcely possible to express, in a few words, the abstracted view of an infinite variety of facts. Dr. Black has defined chemistry to be that science which treats of the changes produced in bodies by motions of their ultimate particles or atoms: but this definition is hypothetical; for the ultimate particles or atoms are mere creations of the imagination. I will give you a definition which will have the merit of novelty, and which is probably general in its application. Chemistry relates to those operations by which the intimate nature of bodies is changed, or by which they acquire new properties. This definition will not only apply to the effects of mixture, but to the phenomena of electricity, and, in short, to all the changes which do not merely depend upon the motion or division of masses of matter." Cuvier, in one of a series of lectures, delivered at Paris, in the Spring of last year, says "the name chemistry, itself, comes from the word chim, which was the ancient name of Egypt;" and he states that minerals were known to the Egyptians "not only by their external characters, but also by what we at the present day call their chemical characters." He also adds, that what was afterwards called the Egyptian science, the *Consolations in Travel; or the Last Days of a Philosopher. 1830. Hermetic art, the art of transmuting metals, was a mere reverie of the middle ages, utterly unknown to antiquity. "The pretended books of Hermes are evidently supposititious, and were written by the Greeks of the lower Empire." Why is chemistry essential to man in his highest state of cultivation? Because every part of his body is covered with the products of different chemical and mechanical arts; made not only useful in protecting him from the inclemency of the seasons, but combined in forms of beauty and variety; creating out of the dust of the earth, from the clay under his feet, instruments of use and ornament; extracting metals from the rude ore, and giving to them a hundred different shapes for a thousand different purposes; selecting and improving the vegetable productions with which he covers the earth; making the winds carry him on every part of the immense ocean; and compelling the elements of air, water, and even fire, as it were, to labour for him; concentrating in small space materials which act as the thunderbolt, and directing their energies so as to destroy at immense distances; blasting the rock, removing the mountain, carrying water from the valley to the hill, &c. Or, to be more minute, the rendering skins insoluble in water, by combining with them the astringent principle of certain vegetables, is a chemical invention; and without leather, our shoes, our carriages, our equipages, would be very ill made: the bleaching and dyeing of wool and silk, cotton and flax, are chemical processes, and the conversion of them into different clothes, is a mechanical invention; the working of iron, copper, tin, lead, and the other metals, and the combining them in different alloys, by which almost all the instruments necessary for the turner, the joiner, the stonemason, the shipbuilder, and the smith, are made, are chemical inventions; even the press could not have existed in any state of perfection without a metallic alloy. The combining of alkali and sand, and certain clays and flints together, to form glass and porcelain, is a chemical process; the colours which the artist employs to frame resemblances of natural objects, or to create combinations more beautiful than ever existed in nature, are derived from chemistry;-in short, in every branch of the common and fine arts, in every department of human industry, the influence of this science is felt; and we may find in the fable of Prometheus taking the flame from heaven to animate his man of clay, an emblem of the effects of fire, in its application to chemical purposes, in creating the activity and almost the life of civil society.—Abridged from "the Last Days of a Philosopher," by the late Sir Humphry Davy. Why may real philosophers be considered to have done much by their own inventions for the useful arts ? Because the chemical or mechanical manufacturer has merely applied what the philosopher has made known; he has merely worked upon the materials furnished to him. Thus, the chlorine, or oxymuriatic gas, of Scheele, was scarcely known, before it was applied by Berthollet to bleaching; scarcely was muriatic gas discovered by Priestley, when Guyton de Morveau used it for destroying contagion. Platinum has owed it existence, as a useful metal, entirely to the labours of an illustrious chemical philosopher; look at the beautiful yellow afforded by one of the new metals, chrome; consider the medical effects of iodine, in some of the most painful and disgusting maladies belonging to human nature, as cancer and bronchocele. We *The improvements of porcelain in this country, as well as those made in Germany and France, have been entirely the result of chemical experiments; the Dresden and the Sèvres manufactories have been the work of men of science; and it was by multiplying his chemical researches, that Wedgewood was enabled to produce, at so cheap a rate, those beautiful imitations, which, while they surpass the ancient vases in solidity and perfection of material, equal them in the elegance, variety, and tasteful arrangement of their forms. |