Compound substances may contain two or more elements. When the composition of a substance is determined by splitting the compound into its elementary constituents a chemical analysis of that substance is said to have been made; and if the proportions by weight in which each of the constituents is present be determined, a quantitative analysis of the substance has been made, etc.
By chemical action, we signify that which occurs when two or more substances so act upon one another as to produce a third substance differing altogether from the original ones in properties; or when a substance is brought under such conditions that it forms two or more bodies differing from the original one in properties. Chemistry is called an experimental science. In investigating all the materials within his reach, whether solid, liquid, or gaseous, whether contained in the earth, sea, or air; whether belonging to the mineral, animal, or vegetable creation, the chemist finds himself obliged to divide substances into two classes: (1) compound substances—those which he is able to split up into two or more essentially different materials; (2) elements or simple substances—those which he is unable thus to split up, and out of which nothing essentially different from the original substances has been obtained.
Compound bodies are made up of two or more elementary substances chemically combined with each other; thus sulphur, copper, lead, are elementary bodies; out of each of these nothing different from sulphur, copper, lead, can be obtained; whereas when two of these bodies are heated together, a compound is formed from which both of the original elementary constituents can at any time be obtained. Water is a compound body—it can be split up into two elementary gases, hydrogen and oxygen; common salt, again, is a compound of a gas (chlorine) with a metal (sodium); and limestone, clay, sugar, and wax may serve as examples of compound bodies; whilst phosphorus, charcoal, iron, mercury, and gold may be mentioned as belonging to the class of simple substances.
As to physical properties of gases—they have weight, volume, diffusion, density, etc.
Theologians insist that there is a God, a God that was first introduced to us by a man with the name of Abraham, advertised by Moses, and has been palmed off upon the masses as a something exceedingly wonderful. A multitude of men who find it to their interest to advocate his pretended claims, are still doing their utmost to sustain their God. We are trying to discover where he is to be found, whether he is a local or a universal God, what he is composed of, whether he resides on earth permanently or transiently, whether he controls the entire solar system or more systems, whether he occasionally takes a trip to other planets; and if he has created everything we want to find out how he has created it. For that reason we have to search, taking a glimpse among the stars, in the earth, atmosphere, etc. Since geology does not respond favorably, we are trying to discover what this earth is composed of. The elementary bodies at present recognized amount to sixty-four in number. Of these about fifty belong to the class called metals. Several of them are of recent discovery, and as yet very imperfectly known. The distinction between metals and certain non-metallic substances or metalloids, although very convenient for purposes of description, is entirely arbitrary, since the classes graduate into each other in the most indefinite manner. The following is a complete list of the elementary substances known, giving their names, symbols, and combining weight:
| Symbols. | METALLOIDS. | Combining Weight. | |||||
| Elements of life: of primary importance. |  | O | Oxygen | [1]II | 16 | ||
| H | Hydrogen | I | 1 | ||||
| N | Nitrogen | V | 14 | ||||
| C | Carbon | IV | 12 | ||||
| Elements of secondary importance. |  | Cl | Chlorine | I | 35 | .5 | |
| Br | Bromine | I | 80 | ||||
| I | Iodine | I | 127 | ||||
| F | Fluorine | I | 29 | ||||
| P | Phosphorus | V | 31 | ||||
| S | Sulphur | VI | 32 | ||||
| Si | Silicon | IV | 28 | ||||
| B | Boron | III | 11 | ||||
| Se | Selenium | VI | 79 | .5 | |||
| Te | Tellurium | VI | 179 | ||||
| Mechanics, arts, science, and medicine. |  | Al | Aluminium | IV | 27 | .4 | |
| Ca | Calcium | II | 40 | ||||
| (Cuprum) | Cu | Copper | II | 63 | .5 | ||
| (Ferrum) | Fe | Iron | IV | 56 | |||
| (Plumbum) | Pb | Lead | IV | 207 | |||
| Mn | Manganese | IV | 55 | ||||
| (Hydrargyrum) | Hg | Mercury | II | 200 | |||
| (Kalium) | K | Potassium | I | 39 | .1 | ||
| (Argentum) | Ag | Silver | I | 108 | |||
| (Natrium) | Na | Sodium | I | 23 | |||
| (Stannum) | Sn | Tin | IV | 118 | |||
| Zn | Zinc | II | 65 | .3 | |||
 | (Stibium) | Sb | Antimony | V | 122 | ||
| As | Arsenic | V | 75 | ||||
| Ba | Barium | II | 137 | ||||
| Bi | Bismuth | V | 210 | ||||
| Cr | Chromium | VI | 52 | .2 | |||
| Co | Cobalt | IV | 58 | .7 | |||
| (Aurum) | Au | Gold | III | 197 | |||
| In | Indium | IV | 74 | ||||
| Mg | Magnesium | II | 24 | ||||
| Ni | Nickel | IV | 58 | .7 | |||
| Pd | [2]Palladium | IV | 106 | .6 | |||
| Pt | Platinum | IV | 197 | .5 | |||
| Sr | Strontium | II | 87 | .5 | |||
| Ti | Titanium | IV | 50 | ||||
| W | Tungsten | VI | 184 | ||||
| U | Uranium | IV | 120 | ||||
| Little known, rarely used. |  | Be | Beryllium | II | 9 | .3 | |
| Cd | Cadmium | II | 112 | ||||
| Cs | Cæsium | I | 133 | ||||
| Cr | Cerium | IV | 92 | ||||
| D | Didymium | II | 95 | ||||
| E | Erbium | II | 112 | .6 | |||
| Ir | Iridium | IV | 198 | ||||
| La | Lanthanum | II | 92 | ||||
| Li | [3]Lithium | I | 7 | ||||
| Mo | Molybdenum | VI | 96 | ||||
| Nb | Niobium | V | 94 | ||||
| Os | Osmium | IV | 199 | .2 | |||
| Rh | Rhodium | IV | 104 | .4 | |||
| Rb | Rubidium | I | 85 | .4 | |||
| Ru | Ruthenium | IV | 104 | .4 | |||
| Ta | Tantalum | V | 182 | ||||
| Tb | Terbium | ||||||
| Tl | Thallium | III | 204 | ||||
| Th | Thorium | II | 231 | .5 | |||
| V | Vanadium | V | 51 | .3 | |||
| Y | Yttrium | II | 61 | ||||
| Zr | Zirconium | III | 89 | .6 | |||
All matter is made up of very small particles which are chemically indivisible and which are termed atoms, and the atom of each elementary substance differs essentially from that of every other. All the atoms of each element are alike, and chemical compounds are formed by the combination of unlike atoms. Hence the smallest particle of a compound consists of a group of atoms. This group, which can be divided by chemical but not by mechanical means, is termed a molecule. The smallest particle of an element in a free state is, however, not a single atom, but a group of atoms mechanically indivisible, or a molecule. This explains why elementary bodies act more energetically and enter more readily into combination at the moment of their liberation from a combination than when in the free state.
When chemical changes occur, it is the molecules which react upon one another, and the change consists in the change of position of certain atoms contained in the groups. When an element is set free from a compound, the liberated join together to form molecules, unless some body is present with which the element can combine.
By an atom we therefore understand the smallest portion of a chemical element which can enter into a chemical compound; by a molecule, the smallest portion of a simple compound body which can occur in the free state or which can take part in a chemical action.
All the elements, with the single exception of fluorine, combine with oxygen to form oxides. In this act of combination, which is termed oxidation, heat is always, and light is frequently, given off. When bodies unite with oxygen, evolving light and heat, they are said to burn, or undergo combustion. All bodies which burn in the air burn with increased brilliancy in oxygen gas; and many substances, such as iron, which do not readily burn in the air, may be made to do so in oxygen.