a healthy condition, and by removing the healthy from contact with the diseased. This form of poison does not appear capable of travelling through the air like that of cholera and influenza. When brought in contact with chlorine, alcohol, sulphurous acid, and when exposed to a temperature even considerably under the boiling point of water, it is rendered inert. According to the opinion of some, the poison of typhus and yellow fever appear capable of passing into the atmosphere in a finely divided state, resembling vapour, and of thus disseminating their influence, and entering into the blood of those exposed to its action. The poison, or seed, will only take effect, however, in a congenial soil; that is, in diseased blood- as in those who have been imperfectly fed, or who have been weakened by over exertion; by an impure diet, or by alcoholic fluids, which interfere with digestion, and debilitate the entire system. EXPLANATION OF CHEMICAL TERMS. A. ABSORPTION (ab from, and sorbeo, I suck up). The entrance of one body between the particles of another, as water into a sponge. ACID. A body which unites with a base. AFFINITY (ad, and finis, allied to). An attraction between two or more bodies. ALCOATE. A combination of alcohol. ALLOTROPY (λos, another, тρоños, habit). A body having dif ferent physical characters; as carbon in its four forms. ALLOY. A compound of two or more metals. AMALGAM. A compound of mercury and another metal. ANALYSIS — (avάλvois). Resolution, or a loosing of the consti tuents. ANNEALING. The process of removing the brittleness from glass. AQUA REGIA. A mixture of 1 part Nitric, and 2 parts Chlo rohydric acids. AQUEOUS. Watery. ATMOSPHERE (αTμos, vapour, and σpaipa, a sphere). B. BALANCE. stances. An apparatus for determining the weights of sub BAROMETER (Bapu, heavy, μeтpov, a measure). A measurer of the weight of the air, fig. 60. BASE. A body which unites with an acid. BASINS. Vessels, more or less deep, for evaporation of porcelain, glass, and metal. BATH. A vessel, containing generally a fluid, which is so arranged as to heat a substance. They may be mercurial, water, steam, or sand. BLOWPIPE. A tube for propelling the flame of a candle or lamp horizontally. C. CAOUTCHOUC. Indian rubber, an exudation from certain trees. CAPILLARY-TUBE. A tube of such small bore as to resemble the diameter of a hair (capilla). CAPSULES. Small basins or vessels of porcelain, glass, or platinum, &c. CATALYSIS (KaTa, from, λvw, I loose). An action of contact or surface. CEMENT. A composition for causing two bodies to adhere; as Parker's, iron, soft. CENTIGRADE, or Celsus. Thermometric scale, in which the freezing point is 0° and boiling point 100o.- To reduce Centigrade to Fahrenheit, multiply by 1.8, and add 32. Thus 50 C × 1·8 = 90.0 + 32 = 122° F. CHARCOAL. The residue from the ignition of wood in close vessels or under cover. CHEMICAL ACTION. The insensible action of one atom of matter on another. COKE. The carbon remaining when coal is burnt in close vessels. CORK BORERS. Cylinders of tin for cutting corks. CRUCIBLE. A vessel for withstanding intense heat, formed of platinum, silver, porcelain, clay, iron, or charcoal. CRYSTAL. A definite form. CUBIC INCH BOTTLE. For measuring the bulk of fluids, and taking specific gravities. D. DECANT. To pour off a fluid from a residue. DECOCTION. The water which has been boiled with an organic substance. DECOMPOSITION. DECREPITATION. A radical change in the composition of a body. The peculiar sound produced when common salt is heated, arising from the sudden extrication of water. DEFLAGRATION. The luminous decomposition of a body by heat; as when nitre is thrown on red hot coals. DENSITY. Specific weight or gravity, fig. 7. DESICCATION. The operation of drying thoroughly. DETONATION. An explosion. DIAMOND-CUTTER. Fragments of diamond made into a paste for cutting glass. DIGESTION. The process of allowing a solid to remain in contact with a fluid, in order to dissolve some portion of it. DIMORPHISM. A body having two crystalline forms. EARTHENWARE. A mixture of clay and flint, used for making vessels. EBULLITION. The act of boiling. EDULCORATION. The act of washing free from salts. EFFERVESCENCE. matter. The rapid escape of a gas, as when vinegar is A measurer of electricity. The relative weight of the ultimate particles of EREMECAUSIS. Slow combustion, as the rotting of trees by the formation of carbonic acid and water. EUDIOMETER. A tube for exploding gases in. EVAPORATION. The conversion of a liquid into vapour. F. FAHRENHEIT'S THERMOMETRIC SCALE. The boiling point 212°; the freezing point 32°. To bring Fahrenheit to Centigrade, subtract 32, and divide by 1.8. Thus 122° F.−32=90÷1·8= 50° C. FILTERING PAPER. Unsized white paper. FILTRATION. The act of passing a fluid through a filter. FLASKS. Thin glass bottles made to stand heat. FLUX. A substance which when heated with another forms a glass, as borax, nitre, black flux, &c. FOIL. Thin leaves of metal. FORMULA. A concise method of expressing the composition of a body. SO, is the empirical, SO2+ 0, the rational formula for sulphuric acid, as expressing the mode of its decomposition. FUEL. A substance which gives out heat when burned. FUNNELS. Conical vessels of glass for the support of filters. FURNACE, An enclosed fire-place of brick, earth, or iron. G. GAS. Any species of air, or elastic fluid. GASOMETER. A fluid measurer or holder of gases. GAUGE. A measure, as a rain gauge. GRADUATION. GRANULATION. GUTTA PERCHA. The act of dividing into degrees. Conversion into grains. An exudation from a tree (Isonandra gutta). Q HYDROMETER. H. A measurer of the density of fluids. HYGROMETER. A measurer of the quantity of moisture in air. HYDRATE. A compound of water and another body, (vdwp, water.) HYDROUS. Applied to a body containing water. HYDRACIDS. IGNITION. Acids containing an element with hydrogen. I. The act of exposing to a red heat. INFUSION. A solution of a substance by digestion in water. INSULATION. Separation by itself. ISOMORPHOUS. Bodies having the same crystalline form, and capable of replacing each other. ISOMERIC. Bodies having the same formula. LAMPS. Vessels for burning oil, alcohol, gas, for the application of heat. LEYDEN JAR. A glass vessel for collecting electricity. LIQUEFACTION. The conversion into a fluid. LITMUS PAPER. Paper coloured with an infusion of litmus, a blue colour. LIXIVIATION. The act of dissolving salts. LUTES. Pastes for connecting tubes. LYE. A solution of caustic alkalies or soap. M. MACERATION. The act of steeping. MAGNETISM. The property which iron may be made to assume of pointing to the north and attracting iron. MELTING. The act of a solid becoming fluid. MORTAR. An instrument of agate, marble, earthenware, iron, or steel, for grinding powders. MUFFLE. A clay vessel for oxidating metals by heat. NEUTRALIZATION. acid nor alkaline. N. The action of rendering a solution neither |