Phlogistic hypothesis, 1st, The whole tenour of the antiphlogistic doctrines necessarily points to such an order; but in considering the facts under other points of view, solutions may be found, which, if not so simple, account for the phenomena with at least equal facility. If hidrogen, according to an hypothesis to which I have often referred, be considered as the principle which gives inflammability, and as the cause of metallization, then our list of simple substances will include oxigen, hidrogen, and unknown bases only; metals and inflammable solids will be compounds of these bases with hidrogen; the earths, the fixed alkalis, metallic oxides, and the common acids, will be compounds of the same bases, with water. Arguments in The strongest arguments in favour of this notion, in addifavour of this. tion to those I have before stated, which at present occur to me, are, First, The properties which seem to be inherent in certain bodies, and which are either developed or concealed, according to the nature of their combinations. Thus sulphur, when it is dissolved in water either in combination with hidrogen or oxigen, uniformly manifests acid properties; and the same quantity of sulphur, whether in combination with hidrogen, whether in its simple form, or in combination with one proportion of oxigen, or a double proportion, from my experiments, seems to combine with the same quantity of alkali. Tellurium, whether in the state of oxide or of hidruret, seems to have the same tendency of combination with alkali; and the alkaline metals, and the acidifiable bases, act with the greatest energy on each other. 2d. Second. The facility with which metallic substances are revived, in cases in which hidrogen is present. I placed two platina wires, positively and negatively electrified from 500 double plates of 6 inches, in fused litharge; there was an effervescence at the positive side, and a black matter separated a the negative side, but no lead was produced; though when litharge moistened with water was employed, or a solution of lead, the metal rapidly formed. The difference of conducting power may be supposed to produce some difference of effect, yet the experiment is favourable to to the idea, that the presence of hidrogen is essential to the production of the metal. Third. Oxigen and hidrogen are bodies, that in all 3d. cases seem to neutralize each other; and therefore, in the products of combustion, it might be expected, that the natural energies of the bases would be most distinctly displayed, which is the case; and in oximuriatic acid, the acid energy seems to be blunted by oxigen, and is restored by the addition of hidrogen. In the action of potassium and sodium upon ammonia, Arguments though the quantity of hidrogen evolved in my experiments against it. is not exactly the same, as that produced by their action upon water; yet it is probable, that this is caused by the imperfection of the process*: and supposing potassium and sodium to produce the same quantity of hidrogen from ammonia and water, the circumstance at first view may be conceived favourable to the notion, that they contain hidrogen, which, under common circumstances of combination, will be repellent to matter of the same kind; but this is a superficial consideration of the subject, and the conclusion cannot be admitted; for, on the idea that in compounds containing gaseous matter, and perhaps compounds in general, the elements are combined in uniform proportions; then, whenever bodies known to contain hidrogen are decomposed by a metal, the quantities of hidrogen ought to be the same, or multiples of each other. Thus in the decomposition of ammonia by potassium and sodium, two of hidrogen and one of nitrogen remain in combination, and one of hidrogen is given off; and in the action of water on potassium to form potash, the same quantity of hidrogen ought There seems to be always the same proportion between the quantity of ammonia which disappears, and the quantity of hidrogen evolved; i. e. whenever the metals of the alkalis act upon ammonia, (supposing this body to be composed of 3 hidrogen, and 1 of nitrogen, in volume, 2 of hidrogen and 1 of nitrogen remain in combination, and 1 of hidrogen is set free. And it may be adduced as a strong argument in favour of the theory of definite proportions, that the quantity of the metals of the alkalis and nitrogen, in the fusible re. sults, are in the same proportions as those in which they exist in the alkaline nitrates. to Composition of sulphuret ted hidrogen. to be expelled. From my analysis of sulphuretted hydrogen it would appear, that, if potassium in forming a combination with this substance sets free hidrogen, it will be nearly the same quantity, as it would cause to be evolved from water. And if the analysis of Mr. Proust and Mr. Hatchett of the sulphuret of iron be made a basis of calculation, iron, in attracting sulphur from sulphuretted hidrogen, will liberate the same proportion of hidrogen as during its solution in diluted sulphuric acid; and taking Mr. Dalton's law of proportion, the case will be similar with respect to other metals: and if such reasoning were to be adopted, as that metals are proved to be compounds of hidrogen, because in acting upon different combinations Containing hidrogen they produce the evolution of equal proportions of this gas, then it might be proved, that almost any kind of matter is contained in any other. The same * The composition may be deduced from the experiments in the last Bakerian lecture, which show, that it contains a volume of hidrogen equal to its own. If its specific gravity be taken as 35 grains, for 100 cubical inches, then it will consist of 2:27 of hidrogen, and 32 73 of sulphur. When sulphuretted hidrogen is decomposed by common electricity, in very refined experiments, there is a slight diminution of volume, and the precipitated sulphur has a whitish tint, and probably contains a minute quantity of hidrogen. When it is decomposed by Voltaic sparks, the sulphur is precipitated in its common form, and there is no change of volume; in the last case the sulphur is probably iguited at the moment of its production. In some experiments lately made in the laboratory of the Royal Institution, on arseniuretted and phosphuretted hidrogen, it was found, that, when these gasses were decomposed by electricity, there was no change in their volumes; but neither the arsenic nor the phosphorus seemed to be thrown down in their common states; the phosphorus was dark coloured, and the arsenic appeared as a brown powder: both were probably hydrurets. This is confirmed likewise by the action of potassium upon arseniuretted and phosphuretted hidrogen: when the metal is in smaller quantity than is sufficient to decompose the whole of the gasses, there is always an expansion of volume; so that arseniuretted and phosphuretted hidrogen contain in equal volumes inore hidrogen than sulphuretted hidrogen, probably half as much more, or twice as much more. From some experiments made on the weights of phosphuretted and arseniuretted hidrogen, it would appear, that 100 cubic inches of the first weigh about 10 grains, at the mean temperature and pressure, and 100 of the second about 15 grains. quantity quantity of potash, in acting upon either muriate, sulphate, or nitrate of magnesia, will precipitate equal quantities of magnesia; but it would be absurd to infer from this, that potash contained magnesia, as one of its elements; the power of repelling one kind of matter, and of attracting another kind, must be equally definite, and governed by the same circumstances. Potassium, sodium, iron, mercury, and all metals, that I have experimented upon, in acting upon muriatic acid gas evolve the same quantity of hidrogen, and all form dry muriates; so that any theory of metallization, applicable to potash and soda, must likewise apply to the common metallic oxides. If we assume the existence of water in the potash formed in muriatic acid gas, we must likewise infer its existence in the oxides of iron and mercury, produced in similar operations. of ammonia of The solution of the general question concerning the The nature of presence of hidrogen in all inflammable bodies will undoubt- the amalgam edly be influenced by the decision upon the nature of the importance in amalgam from ammonia, and a matter of so much im- deciding the question. portance ought not to be hastily decided upon. The difficulty of finding any multiple of the quantity of oxigen, which may be supposed to exist in hidrogen, that might be applied to explain the composition of nitrogen from the same basis, is undoubtedly against the simplest view of the subject. But still the phlogistic explanation, that the metal of ammonia is merely a compound of hidrogen and nitrogen; or that a substance which is metallic cau be composed from substances not in their own nature metallic, is equally opposed to the general tenour of our chemical reasonings. I shall not at present occupy the time of the Society, by entering any farther into these discussions; hypothesis can scarcely be considered as of any value, except as leading to new experiments; and the objects in the novel field of electrochemical research have not been sufficiently examined, to enable us to decide upon their nature, and their relations, or to form any general theory concerning them, which is likely to be permanent. teries. III. The Croonian Lecture. On the Functions of the Heart and (Concluded from p. 68.) I shall proceed to inquire, in the third place, into the na Functions of the muscular ture and extent of the functions, which are to be attributed fibres of the coats of the ar- to the muscular fibres of the coats of the arteries; and I apprehend, that it will appear to be demonstrable, that They have less effect on the they are much less concerned in the progressive motion of motion of the the blood, than is almost universally believed. The argublood, than is ments, which may be employed to prove this, are nearly generally supposed the same that I have already stated, in examining the moArguments to tion of a fluid, carried along before a moving body in an prove this. open canal; but in the case of an elastic tube, the velocity of the transmission of an impulse being rather diminished than increased by an increase of tension, the reasoning is still stronger and simpler; for it may here be safely asserted, that the anterior parts of the dilatation, which must be forced along by any progressive contraction of the tube, can only advance with the velocity appropriate to the tube, and that its capacity must be proportionate to its length and to the area of its section: now the magnitude of its section must be limited by that degree of tension, which is sufficient to force back through the contraction what remains of the displaced fluid; and the length, by the difference of the velocity appropriate to the tube, and that with which the contraction advances: consequently, if the contraction advance with the velocity of a pulsation, as any contractile action of the arteries must be supposed to do, this length necessarily vanishes, and with it the quantity of the fluid protruded; the whole being forced backwards, by the distending force which is exerted by a very small diSupposition, lated portion immediately preceding the contraction. It traction follows might indeed be imagined, that the contraction follows the the pulsation pulsation with a velocity somewhat smaller than its own; but this opinion would stand on no other foundation than that the con with less velo city; mere |