111 MURIATIC ACID. Potash Soda Lime Magnesia SULPHURIC ACID. Soda Baryta NITRIC ACID. Potash Soda Lime Lime Magnesia Ammonia Alumina Magnesia Ammonia Alumina Alumina He gave also two tables of his famous double elective attraction, or compound attraction. The examples given are numerous, and would take too much room. The form is exactly the same as given below as Elliot's, no numbers being used. Elliot published Bergman's tables, with the addition of figures, to show the relative force which one bore to another. He says, "suppose that (see Encycl. Method. Dict. de Chymie, vol. i., p. 552) potash and sulphuric acid attract each other with the force of 9; that oxide of silver and nitric acid attract each other with the force of 2; that the affinity of nitric acid, with potash, is 8, and that of sulphuric acid, with oxide of silver, 4. As 8+ 4 is greater than 9+ 2, decomposition takes place, and two new compounds are formed, nitrate of potash and sulphate of silver." He then made the symbols so:— G. Morveau continued this schema or symboles, finding new numbers, and he has put into a short table his results. This is a more definite way of showing the relation of bodies to each other than we have yet seen. Table of the numerical expression of the affinities of five Acids and seven Bases, according to the constant relations indicated by the most familiar observations.* "the At the same time he says,† relating to the figures, numbers which I have employed have no certain basis, but because they agree with a sufficient number of the most familiar observations, they may be used without inconvenience, until we recognise the necessity of changing them, so as to make them agree with other results." Fourcroy gave numbers also on similar principles, but Morveau objects to them as being so small that it was not easy to find intermediate ones, whilst he objects to Kirwan's numbers which gave the weight of the base as the amount of the affinity, because this did not agree with results. In these schemes of double decomposition there seems to be a tacit agreement, that the acid which saturated one base, would saturate the second. Kirwan experimented very much in the direction which Bergman had followed. He is another of those who nearly discovered the atomic theory, who laboured in a legitimate direction, but whose discoveries and theories on the subject are merged in the higher and simpler law. A brief extract will give his results. "The discovery of the quantity of real acid in each of the mineral acid liquors, and the proportion of real acid taken up by a given quantity of each basis at the point of saturation, led me, unexpectedly, to what seems to be the true method of *Dict, de Chymie, Vol. I., p. 558. † Page 557. investigating the quantity of attraction which each acid bears to the several bases to which it is capable of uniting; for it was impossible not to perceive, first, that the quantity of real acid, necessary to saturate a given quantity of basis, is inversely as the affinity of each basis to each acid. 2ndly. That the quantity of each basis, requisite to saturate a given quantity of each acid, is directly as the affinity of such acid to each basis. Thus 100 grains of each of the acids require for their saturation a greater quantity of fixed alkali than of calcareous earths, more of this earth than of volatile alkali, more of this alkali than magnesia, and more of magnesia than of earth or alum, as may be seen in the following table. Quantity of Basis taken up by 100 grs. of each of the Mineral Acids. "As these numbers agree with what common experience teaches us concerning the affinity of these acids with their respective bases, they may be considered as adequate expressions of the quantity of that affinity, and I shall in future use them as such. Thus the affinity of vitriolic acid to fixed vegetable alkali, that is, the force with which they unite, or tend to unite, to each other, is to the affinity with which that same acid unites to calcareous earth, as 215 grs. to 110; and to that which the nitrous acid bears to calcareous earth as 215 grs. to 96," &c.* He adds a similar table of metals and acids. Kirwan gives here what would lead to the atomic weights of the bodies had he known the law which appears to have been first published by Richter; one obtained the atomic weights as the measure of affinities, the other reciprocal * Philosophical Transactions Abridged, Vol. XV., p. 335-6, year 1783. This was read, I believe, in 1782. affinities, but neither knew the other's results, and both were lost sight of. The one (Ritcher) did not know that he had got close upon a universal law, the other (Kirwan) did not know that he had got the mode of expressing that universal law, but used it for what it was little worth, an expression of affinity. We now come to Wenzel, one of those men whose names have been brought forward as a much neglected philosopher, and to whom almost every writer on the history of science, who has had occasion to mention him in later years, has been anxious to award the due honour. We see his book constantly quoted. Some writers give us his words, others give us what appears such a clear explanation of his ideas that we feel no more to be wanting. I had been long anxious to obtain his works, but after advertising in Germany, and inquiring in several towns and large libraries in this country, as well as in France and Germany, I did not obtain the volume, and proceeded without it. I afterwards found that a duplicate copy existed at the Munich Royal Library, and was fortunate enough to obtain it, duplicate copies being generally disposed of. Having read it carefully over, I found no such passages as are imputed to him; and, therefore, read it still more carefully again, and then a third time, but they did not exist. Having written to two eminent historians of science for an explanation, I find that neither had seen the volume; but one of them informed me that the mistake had been rectified in a supplement to the "Handwoerterbuch der Chemie u. Physik."* The reciprocal saturation which results when two salts decompose each other, is the discovery, the honour of which has long been given to Wenzel. It is a curious fact that not only does he not see this, but he sees and explains the con It is by Dr. J. S. C. Schweigger, and has been since published as a pamphlet (Ueber die Stoechiometrische Reihen im Sinne Richter's), &c., Halle, 1853. trary, as he shews us that in double decomposition something always remains unsaturated; but generally very little remains. One is sorry that being so near a law, he had not the slightest conception of it. The most important part of his work, as far as our purpose is concerned, seems to me to be contained in the following sentences. The title of the work is "The Doctrine of the Affinity of Bodies." I shall not give the original, although scarce, as the work, from the fact above stated, has lost its great importance. In the Preface, he 66 says, at first my only intention was to make for my own use a treatise which should contain the order of the ascertained affinities and the circumstances under which they acted, lest I should not be able to remember them. But it occurred to me that others might find it useful also, if it were more worked out. For this end I endeavoured to explain the cause and the law of affinity on a good foundation, and the circumstances under which the bodies combine as well as the true relation of their weights towards each other. Page 4. "It is of itself clear that any combination of bodies must have a constant unchangeable proportion, which can neither be greater nor smaller without some cause acting externally, because, otherwise, nothing certain could be decided on by comparing them. It therefore necessarily follows, that every possible combination of two bodies stands in the most exact relationship with every other, and this relation expresses the degree of combination. Page 9. "These smallest particles of each body have at all times, in a natural state, a determinate figure; but the whole mass of the body takes a form according as chance or art gives it, without causing any change in the smallest particles, just as the tender fibres or tubes in a piece of wood remain always the same, although the whole piece may be in the shape of a ball or a cube." Carl Friedrich Wenzel, Lehre von der Verwandschaft der Koerper. Dresden, 1777. Y |