CHEMISTRY. 



173 



vegetable kingdom, which analyzes plants and their 

 immediate products ; and a chemistry of the animal 

 kingdom, which studies all substances derived from 

 living and dead animals. This last is subdivided 

 into ' physiological chemistry, which considers the 

 changes produced in animal substances by the opera- 

 tion of life ; pathological chemistry, which traces the 

 changes produced by disease or organic defects; 

 therapeutic or pharmaceutic chemistry, which teaches 

 the nature and preparation of medicines, shows the 

 means of preserving them, and exposes the preten- 

 sions of empirics; hygietic chemistry, which acquaints 

 us with the means of constructing and arranging our 

 habitations, so as to render them healthy, of examin- 

 ing the air which we must breathe in them, guard- 

 ing against contagious diseases, choosing wholesome 

 food, discovering the influence of occupation, fashion, 

 and custom on the health. Agricultural chemistry 

 treats of the nature of plants and soils, and the laws 

 of production. Sir Humphrey Davy first gave it the 

 character of a science. It treats, 1. of the general 

 powers of matter which have any influence on vege- 

 tation, of gravity, cohesion, chemical affinity, heat, 

 light, electricity, the elements of matter, especially 

 such as are found in vegetables, and the laws of their 

 composition and arrangement ; 2. of the organiza- 

 tion of plants, their structure, the chemical compo- 

 sition of their organs, and the substances found in 

 them, &c. ; 3. of soils ; 4. of the nature of manure. 



Chemistry, finally, exerts an influence on the rou- 

 tine of domestic life, and on the arts. It simplifies 

 and regulates the daily offices of the housekeeper ; 

 renders our dwellings healthy, warm, light ; assists 

 us in preparing clothing, food, drink, &c. : it teaches 

 the best way of making bread ; preparing and puri- 

 fying oils ; of constructing bakehouses, ovens, and 

 hearths ; of bleaching and washing all kinds of stuff; 

 of producing artificial cold, &c. The application of 

 chemistry to the arts and manufactures is, however, 

 still more important and extensive. Here its aim is 

 to discover, improve, extend, perfect, and simplify 

 the processes by which the objects to be prepared 

 may be adapted to our wants. We close our re- 

 marks with the observation, that a knowledge of 

 chemistry may frequently be useful in judicial pro- 

 ceedings, in exposing crime; e. g., in cases of 

 poisoning, counterfeiting coins and written docu- 

 ments, &c. 



Chemical Classification and Nomenclature. The 

 chemist finds a small number of bodies, from which 

 only one kind of matter can be obtained, in the pre- 

 sent state of his knowledge, and by the instruments 

 and agents which he now has at his disposal. On 

 the other hand, there is a large number of bodies, 

 from which he obtains several kinds of matter. The 

 former he calls elements or simple bodies ; the latter, 

 compound bodies. The number of simple bodies now 

 known is fifty-three : that of the compounds is much 

 greater, and might, at first, appear to be infinite, 

 since not only a difference of elements, but even a 

 difference of the proportions in which they are com- 

 bined, makes an essential difference hi the properties 

 of the compound. It is, however, much less than 

 would be supposed, and even less than the number 

 of possible combinations of simple bodies. Twelve 

 of the simple bodies are oxygen, iodine, chlorine, 

 bromine, fluorine, hydrogen, ooron, carbon, phos- 

 phorus, sulphur, azote, and selenium ; and forty-one 

 are metals (q. v.). The five first are called support- 

 ers of combustion, because they combine with the 

 others, producing a disengagement of heat and light, 

 and acidifying principles, because they are also capa- 

 ble' of producing acids by a similar combination. 

 The forty-eight others are called simple combustibles, 

 because their union with the supporters of combus- 



tion, above mentioned, is a real combustion. Com- 

 pound bodies, as has been observed, are not so 

 numerous as might be supposed. They result, 1. 

 from the combination of oxygen, or one of the other 

 simple supporters of combustion, with one of the 

 simple combustibles; such are the acids: 2. from 

 that of a simple body combined with oxygen, with 

 another similar compound; such are the salts: 3. 

 from that of two, three, rarely four, simple combus- 

 tibles with one another : 4. from that of oxygen with 

 hydrogen and carbon, forming vegetable matter : 5. 

 from that of oxygen with hydrogen, carbon, and azote, 

 forming animal matter. Combustibles combined 

 with the simple supporters of combustion are some 

 times called burned bodies ; from the number of their 

 elements, they are also called binary compounds. 

 When their taste is acid, and they have the property 

 of reddening vegetable blues, they are termed acids. 

 If they are not acid to the taste, and have the pro- 

 perty of turning blue what has been reddened by 

 acids, they are distinguished by the termination ide, 

 as oxide, chloride, &c. If only one of the latter class 

 is formed, that is, if the supporter of combustion will 

 unite with the combustible in only one proportion, 

 we call this compound simply the oxide, chloride, &c., 

 of the combustibles ; as, oxide of carbon. If they 

 unite in several proportions, we call the first, or that 

 which contains the smallest proportion of oxygen, 

 &c. , protoxide, &c. ; the second, deutoxide ; the 

 third, tritoxide. The highest is also called per- 

 oxide. So, if only one acioT is formed, we designate it 

 by the name of the combustible, with the termination 

 ic. Thus carbon with oxygen forms carbonic acid. 

 If several are formed, that which contains the larger 

 proportion of the acidifying principle is designated 

 by the termination ic, and that which contains less, 

 by the termination ous. Thus sulphur forms sul~ 

 ,phuric acid and sulphurous acid. If there are still 

 intermediate compounds, we annex hypo (signifying 

 less), to designate a lower degree of acidity. Thus 

 we should have sidphuric, hyposulphuric ; sulphur- 

 ous, hyposulphurous. In the acids and oxides, chlor- 

 ides, &c., the combustible is called the base. When 

 the base is the same, the peroxide, &c., always con- 

 tains less oxygen, &c., than the lowest acid. For 

 the names of compounds of two binary burnt bodies, 

 no rules have been adopted to express the union of 

 two oxides, two acids, or an acid with a non-metallic 

 oxide. But those formed of acids and metallic oxides 

 are called salts, and their individual names are form- 

 ed by changing the termination of the acid and plac- 

 ing it before the name of the metal ; the termination 

 ous is changed into ite, and ic into ate ; sulphurous 

 acid with the oxide of tin would form sulphite of tin ; 

 sulphuric acid and tin, sulphate of tin. If the same 

 acid combines with more than one oxide of the same 

 metal, then we prefix the characteristic of the oxide 

 to the name of the acid ; thus sulphuric acid, com- 

 bined with the protoxide of iron, forms the protosul- 

 phate, with the peroxide, the persulphate, of iron. 

 Other substances have also the property of uniting 

 with acids, neutralizing them, and forming compounds 

 analogous to salts. There are no general rules for 

 the names of these compounds ; but the substances 

 themselves are called salifiable bases. The rules of 

 nomenclature, in regard to the combination of the 

 combustibles, vary : 1 . If the constituents are metais, 

 they form alloys. 2. If the compounds are solid or 

 liquid, and formed of a metallic and a non-metallic 

 combustible, we give to the latter the termination 

 uret ; as, carbon with iron forms carburet of iron, li 

 both are non-metallic, the termination uret may be 

 attached to either; as, phosphuret of sulphur, or 

 sulvhuret of phosphorus. 3. If the compound is 

 gaseous, we name the gas or one of the gases, if it 



