Fig. 1.Fig. 2Fig. 3.
Fig. 1 is a compound atom of Sulphuric Acid, consisting of an atom of Sulphur united intimately with three of Oxygen; fig. 2 is an atom of Peroxide of Nitrogen, NO4; and fig. 3, an atom of Nitric Acid, composed of Nitrogen 1 atom. Oxygen 5 atoms, or in symbols NO5.
The term "atomic weight" substituted for equivalent proportion.—If we suppose that the simple atoms of different kinds of matter differ in weight, and that this difference is expressed by their equivalent numbers, the whole laws of combination follow by the simplest reasoning. It is easy to understand that an atom of one element, or compound, would displace, or be substituted for, a single atom of another; therefore, taking as the illustration the decomposition of Iodide of Potassium by Chlorine,—the weight of the latter element required to liberate 126 grains of Iodine is 36 grains, because the weights of the atoms of those two elementary bodies are as 36 to 126. So again, in the reaction between Chloride of Sodium and Nitrate of Silver, a compound atom of the former, represented by the weight 60, reacts upon a compound atom of the latter, which equals 170.
Therefore in place of the term "equivalent" or "combining proportion," it is more usual to employ that of "atomic weight." Thus the atomic weight of Oxygen is 8, represented by the symbol O; that of Sulphur is 16; hence the atomic weight of the compound atom of Sulphuric Acid, or SO3, is necessarily equal to the combined weights of the four simple atoms; id est, 16 + 24 = 40.
ON THE CHEMISTRY OF ORGANIC SUBSTANCES.
By "organic" substances are meant those which have possessed life, with definite organs and tissues, in contra-distinction to the various forms of dead inorganic matter, in which no structural organization of that kind is found.
The term organic however is also applied to substances which are obtained by chemical processes from the vegetable and animal kingdoms, although they cannot themselves be said to be living bodies; thus Acetic Acid, procured by the distillation of woody fibre, and Alcohol, by fermentation from sugar, are strictly organic substances.
The class of organic bodies embraces a great variety of products; which, like inorganic Oxides, may be divided into neutral, acid, and basic.
The organic acids are numerous, including Acetic Acid, Tartaric, Citric, and a variety of others.
The neutral substances cannot easily be assimilated to any class of inorganic compounds; as examples, take Starch, Sugar, Lignine, etc.