To express the composition of a compound body, Berzelius has proposed signs, by means of which, a glance will suffice to show what otherwise must have required a long periphrase to enunciate. Each radical is represented by the initial of its Latin name. If two radicals have the same initial letter, they are distinguished in the following manner. Combustible bodies, not metallic, are designated by the first letter alone ; such metals as have the same initial being distinguished by a second letter. Thus C denotes carbon ium ; Co. = cobalt ; Cu.= cuprum ; Sn. = Stannum ; Sb.= subium ; 0 signifies oxygen ; but as in compound bodies it is a more general ingredient than any other element, Berzelius proposes to mark the num ber of its atoms by dots placed above the initial letter. Thus, for example, &= C 2 0= carbonic acid ; Fe = Fe ± 30 = red oxyd of iron. This expedient renders the formula shorter and more easily understood. When a compound body contains several molecules of a conMust ible element, the number of its atoms i, annexed on the . 7 right, like an exponent in algebra. Thus, .41. = SU!.
phatc of alumina, means that there are three molecules of sulphur or sulphuric acid for one of alumina ; but if it were required to denote that a body contains, for example, two particles of the sulphate of alumina, the number is placed on the left ; and it then multiplies all the letters which follow it. Thus, A. S. + 2 4/. is the formula, exhibiting the composition of alum. To determine the relative weight of the molecules, Berzelius compares them with that of oxygen, supposed to be unity ; a method which has likewise been proposed by Dr. Wollaston. The number of molecules contained in an oxyd being known, it is easy to find the w eight of molecule of the radical. The oxyd of iron, for instance, is composed of 100 parts iron, and 44.25 parts oxygen : these 44.25 parts form three molecules of oxygen ; from which it follows that : 100 : : 1, (the weight of oxygen,) : 6.78, the weight of the molecule of iron. NI. Berzelius has given the following table, exhibiting the weight of the several radicals, and the composition as well as weight of their oxyds.
But we have still to discuss a very important point in regard to the corpuscular hypothesis, and its application to observed facts. Admitting that bodies are composed of entire atoms, in all the following modes: 1 A for example with 1 A, 2 A with 3B, 3 A with 4 B, or 5, or 7, or 8, or 9 B, A with 10 B, and lastly 99 A with 100 B; it fol lows, that combinations may take place according to an almost infinite number of proportions, the differences of which would finally become such, that no analysis could be exact enough to discover them. This, however, does not, in fact, take place; consequently the molecules cannot combine, (at least in the case of inorganic substances,) in all numbers whatever; and, therefore, it is necessary to inquire what are the proportions, according to which the molecules of elementary bodies are found actually com bined. On surveying the analyses hitherto made of inor
ganic substances, Berzelius thinks he has found that nearly all of them are compounded in such a way, that one of the elements occurs only in a single molecule; and from this fact he has drawn the conclusion, hat such substances are characterized in their composition by the circumstance of one element, in comparison with the rest, always entering by a single molecule. Some exceptions to this rule were at first considered by him as proceeding from our inade quate acquaintance with the number of molecules in such bodies ; but after a more comprehensive examination, he is of opinion that there exist combinations of two molecules of one element, with three of another ; which, however, he in clines to believe do not occur between two elements alone, but require the pressure of a third to effect their union. Thus the subsulphate of oxyd of copper is composed of 3 Cu. + 2 8, whilst no combination of 3 Cu. + 2 S, is known to exist, or can exist, as Berzelius thinks ; because nothing more than a force purely mechanical seems requisite to divide it into one molecule of S C, and one of S 2 C. A priori, it cannot be decided whether, in the compass of inorganic nature, molecules do not combine in still more complicated numbers; such as 3 4 + 4 B, + 5 B, &c. &c.; but so far as actual experience allows us to decide, it is reasonable to suppose that no such combinations occur. On attempting to discover the cause why the molecules, in all inorganic substances, combine only according to pro portions so limited, we arrive at certain boundaries, over which it is not permitted for the present to extend the empire of science. We cannot explain how it happens, that if oxygen be added to a solution, say of (= the subsulphate of the protoxide of iron,) there results not an . Fe S2, hut a division of the compound into Fe S' and j%ez The phenomenon naturally depends no less on the forces which cause the elements to combine, than on the change of Corm produced upon the new molecules created by the addition of oxygen ; and so long as we remain ignorant of the greater part of what concerns these two circumstances, we shall be obliged to content ourselves with simply knowing the facts. It is alike blamable not to speculate at all about the causes of phenomena, and to push the speculation to a length, where, no longer being guided by experiment, it becomes altogether fictitious and imaginary.