CHYMISTRY. The science which teaches the composition and properties of material substances, together with the changes they undergo. The extensive utility of this science is shown by its immediate connection with the arts, subservient to the subsistence or the com forts of man. Dying, bleaching, tanning, glassmaking, the working of metal; &c. are chymical operations. In agriculture Its use is very important, because it explains the phe nomena of the action of manure, &c. The culinary arts, the arts of baking, brewing, distilling, &c. owe their improvement to chym istry. In medicine it affords invaluable as sistance, by giving the medical man a know ledge of the various substances used as medi cines. In short, there is scarcely any art, trade, or manufacture, that does not depend, either immediately or remotely, upon the knowledgeof this science. Besides, it enlarges the mind, by affording us a more extensive and intimate knowledge of nature, and pro cures for us some of the most sublime plea sures and rational enjoyments. Chymista now distinguish bodies generally into simple and compound substances.
Simple substances comprehend such as have hitherto not been decompounded. Of these some are denominated combustibles, because they can undergo combustion, or, Mother words, can burn, as hydrogen, carbon, phosphorus, and borax, besides the alkalis, earths and metals. Some are supporters of combustion, which, though not of themselves capable of undergo ing combustion, are necessary to produce this effect in other bodies, of which there are three, namely, the three gaseous bodies, oxygen, chlorine, and iodine. There is one body, namely, azoteor nitrogen gas, which is proper ly an incombustible, because it neither under goes combustion in itself, or supports it in other bodies. To this list of simple substances must be added four others, which are consi dered as such by modern chymists, namely, light and heat, which were formerly looked upon as properties of matter, and electricity and galvanism. Light, beat, and electricity, are powerful chemical agents, which produce the most important phenomena.
Compound substances are formed by the union of simple substances with each other, or by that of compound substances with others. That which forms the basis as it were of the combination in this case, is denominated the base or radical ; this may either be en acidifia ble base or a salifiable base ; thus phosphorusis the acidifiable base in phosphoric acid, and pot ash is the salifiable base in the sulphate of pot ash. Acids hold the first rank among the compounds. These are formed by the combina tion of oxygen with some acidifiable base, and are distinguished according to the proportion of the oxygen which enters into the acid by the terminations is and ous, as nitric acid and ni trous acid, sulphuric acid and sulphurous acid, &c., the former of which, namely, the nitric and sulphuric acid, denote the large dose or por tion of the oxygen ; the latter, namely, nitrous acid, the smaller portion. There are also me tallic bases, which are distinguished by the termination um, as potassium, the base of pot sodhim, the base of soda. When the compounds possess no sensible properties of an acid, the co?chinations with oxygen, chlorine, and iodine, form a class of compounds diode by the termination ids, if they are supporters of combustion, and et if they are combustibles, as the oxide, chloride, or 'iodide of amenia potash, soda, itc., the salphuret of
potassium, phosphoret of carbon, &c.
Acids for the mem part combine with lies, earths, and metallic oxides, and form an other important class of campotmds called salts ; these are distinguished by iy the termn st-1 den oleic when the acid contains the larger portion of oxygen, and that of he when the acid contains the smalls portion ' • thus the combination of sulphuric acid and potash is a sulphate of potash, and that of sulphurous acid with potash is a sulphite of potash Salts are denominated neutral when. the separate quali ties of the component principles are not appa• rent, but when the acid prmi'mm, the pre fix super is added, and when the base pre dominates it is denoted by the prefix sob ; thus the sulphate of potash denotes the salt in its perfect state, without any excess oldie sul phuric acid or the potash ; the sapersalphate of pxm-h is the setae salt with an excess of acid; the sulselphate of potash is the same salt with an excess of base. When an acid combines with two bases, this clam of com pounds is distiagnislbed by the name of triple skis, = the tartrate of potash and soda, that ls, the combiumioa of tartaric acid with potash and soda.
The ownlinatioas of metals with each other are called alloys, except those which mercury forms with any other metal, which are called on To this list of compound substances most be added several compound combustibles, as alcohol, ether, resins, bitumens, oils, and also some formed by the combination of fixed oils with alkalies, earth, and metallic oxide. Be sides, water and atmospheric air, which had heretofore been looked upon as stances, arenew ranked among the compormds Cmial action consists of two parts, namdy, deoonapoiLion and combination. When the constituent parts of bottles are sepa rated from each other, the bodies are said to he deoomposed, and the act of separating them is called decompothion : on the other hand, when bodies are so intimately united as to form new and distinct substances, this thymic:ad union is rfistiaguirthed by the name of combination. The ciwmical inrestiganen of buries, therefore, proceeds in two ways, namely, by analysis, that is, the !operation of bodies by a series of decompositions and otmkinzrions, to crane at the knowledge of the constituent parts; and synthesis, by a series of processes to form new compounds ; and these two forms of in vestigaticn may accompany and assist each other : Epsoln salts may be analyzed and shown to consist of sulphuric acid and mag nesia, or it may be synthetically compounded by combining magnesia with salpittoic acid, when Epsomsilts, in the farm of crywals,, will be the revolt Chymical investigations proceed on the principle of attraction, in its different forms of affinity, cohezion, ide, and also oa that of repulsion. The different process required in this unestigatiMi are stibnite), necaraliza. tion, prmiptation, a,, distills filth" sablimation, litiriation, reduction, edelaration, dement:ion, fulmination, tie, each of which teams may be found explained in its prope. place