The following general rules may be adopted as guides in all our investigations respecting chemical synthesis. Ist. When only one combination of two bodies can be obtained, it must be presumed to be a binary one, unless some cause appear to the contrary. 2d. When two combinations are observed, they must be presumed to be a binary and a ternary. 3d. When three combinations are obtained, we may expect one to be a binary, and the other two ternary. 4th. When four combinations are observed, we should expect one binary, two ternary, and one quaternary, &c. 5th. A binary compound should always be specifically heavier than the mere mixture of its two ingredients. 6th. A ternary compound should be specifically heavier than the mixture of a binary and a simple, which would, if combined, constitute it; &c. 7th. The above rules and observations equally apply, when two bodies, such as G and D, D and E, &c. are combined. From the application of these rules, to the chemical facts already well ascertained, we deduce the following conclusions: Ist. That water is a binary compound of hydrogen and oxygen, and the relative weights of the two elementary atoms are as : 7, nearly; 2d. That ammonia is a binary compound of hydrogen and azote, and the relative weights of the two atoms are as 1: 5, nearly; 3d. That nitrous gas is a binary compound of azote and oxygen, the atoms of which weigh 5 and 7 respectively; that nitric acid is a binary or ternary compound according as it is derived, and consists of one atom of azote and two of oxygen, together weighing 19; that nitrous oxide is a compound similar to nitric acid, and consists of one atom of oxygen and two of azote, weighing 17; that nitrous acid is a binary compound of nitric acid and nitrous gas, weighing 31; that oxynitric acid is a binary compound of nitric acid and oxygen, weighing 26; 4th. That carbonic oxide is a binary compound, consisting of one atom of charcoal, and one of oxygen, together weighing nearly 12; that carbonic acid is a ternary compound, (but sometimes binary) consisting of one atom of charcoal, and two of oxygen, weighing 19; &c. &c. In all these cases the weights are expressed in atoms of hydrogen, each of which is denoted by unity. In the sequel, the facts and experiments from which these conclusions are derived, will be detailed; as well as a great variety of others from which are inferred the constitution and weight of the ultimate particles of the principal acids, the alkalis, the earths, the metals, the metallic oxides and sulphurets, the long train of neutral salts, and in short, all the chemical compounds which have hitherto obtained a tolerably good analysis. Several of the conclusions will be supported by original experiments. From the novelty as well as importance of the ideas suggested in this chapter, it is deemed expedient to give plates, exhibiting the mode of combination in some of the more simple cases. A specimen of these accompanies this first part. The elements or atoms of such bodies as are conceived at present to be simple, are denoted by a small circle, with some distinctive mark; and the combinations consist in the juxtaposition of two or more of these; when three or more particles of elastic fluids are combined together in one, it is to be supposed that the particles of the same kind repel each other, and therefore take their stations accordingly. Enough has been given to shew the method; it will be quite unnecessary to devise characters and combinations of them to exhibit to view in this way all the subjects that come under investigation; nor is it necessary to insist upon the accuracy of all these compounds, both in number and weight; the principle will be entered into more particularly hereafter, as far as respects the individual results. It is not to be understood that all those articles marked as simple substances, are necessarily such by the theory; they are only necessarily of such weights. Soda and Potash, such as they are found in combination with acids, are 28 and 42 respectively in weight; but according to Mr Davy's very important discoveries, they are metallic oxides; the former then must be considered as composed of an atom of metal, 21, and one of oxygen, 7; and the latter of an atom of metal, 35, and one of oxygen, 7. Or, soda contains 75 per cent. metal and 25 oxygen; potash, 83.3 metal and 16.7 oxygen. It is particularly remarkable, that according to the above-mentioned gentleman's essay on the Decomposition and Composition of the fixed alkalies, in the Philosophical Transactions (a copy of which essay he has just favoured me with) it appears that "the largest quantity of oxygen indicated by these experiments was, for potash 17, and for soda, 26 parts in 100, and the smallest 13 and 19.' The figure [32] for sulphuretted hydrogen is incorrect: it ought to be I atom of hydrogen instead of 3, united to 1 of sulphur. See list. The plate opposite contains the arbitrary marks or signs chosen to represent the several chemical elements or ultimate particles. 21. An atom of water or steam, composed of 1 of oxygen and I of hydrogen, retained in physical contact by a strong affinity, and supposed to be surrounded by a common atmosphere of heat; its relative weight I I .8 22. An atom of ammonia, composed of 1 of azote and 1 of hydrogen......6 23. An atom of nitrous gas, composed of 1 of azote and 1 of oxygen...12 24. An atom of olefiant gas, composed of 1 of carbone and I of hydrogen...6 25. An atom of carbonic oxide composed of 1 of carbone and I of oxygen 12 26. An atom of nitrous oxide, 2 azote + 1 oxygen. I I .17 27. An atom of nitric acid, 1 azote + 2 oxygen ...... 19 28. An atom of carbonic acid, 1 carbone +2 oxygen 19 29. An atom of carburetted hydrogen, 1 carbone +2 hydrogen ...... .7 30. An atom of oxynitric acid, 1 azote + 3 oxygen .26 31. An atom of sulphuric acid, I sulphur +3 oxygen .34 32. An atom of sulphuretted hydrogen, 1 sulphur +1 hydrogen............16 33. An atom of alcohol, 3 carbone +1 hydrogen ...16 ......... 34. An atom of nitrous acid, 1 nitric acid + 1 nitrous gas .........3I 35. An atom of acetous acid, 2 carbone +2 water......... ..........26 36. An atom of nitrate of ammonia, 1 nitric acid + 1 ammonia + 1 water 33 37. An atom of sugar, 1 alcohol + 1 carbonic acid ..35 THE COMBINATION OF GASES EXPERIMENTS on the relative weights in which chemical elements combine sufficed to lead Dalton to his modern revival of the atomic theory. But such experiments alone would have failed to bring to light all the laws of chemical action and all the inferences which may be drawn from them. In a new problem it is always well to begin by examining the simplest case in which it appears. The great merit of the work of the distinguished French chemist Gay-Lussac on the combination of gases lies in his appreciation of the fact that in gases, or elastic fluids as he calls them, the disturbing force of cohesion is negligible, so that the phenomena of chemical combination appear in their simplest form. MEMOIR ON THE COMBINATION OF GASEOUS SUBSTANCES WITH EACH OTHER (Read before the Philomathic Society, 31st Dec., 1808.) SUBSTANCES, whether in the solid, liquid, or gaseous state, possess properties which are independent of the force of cohesion; but they also possess others which appear to be modified by this force (so variable in its intensity), and which no longer follow any regular law. The same pressure applied to all solid or liquid substances would produce a diminution of volume differing in each case, while it would be equal for all elastic fluids. Similarly, heat expands all substances; but the dilatations of liquids and solids have hitherto presented no regularity, and it is only those of elastic fluids which are equal and independent of the nature of each gas. The attraction of the molecules in solids and liquids is, therefore, the cause which modifies their special properties; and it appears that it is only when the attraction is entirely destroyed, as in gases, that bodies under similar conditions obey simple and regular laws. At least, it is my intention to make known some new properties in gases, the effects of which are regular, by showing that these substances combine amongst themselves in very simple proportions, and that the contraction of |