the surrounding bitumen, and that this charcoal, besides its concentration, is combined with a fresh dose of azot, so as to have lost that prompt and easy combustibility that characterizes the charcoal of our woods, we might flatter ourselves that we possessed an argument of much weight in favour of the opinion that we seek to remove, and then we should be less surprized to find in pit-coal this astonishing result of their metamorphosis, sixty, seventy, or eighty per cent. of charcoal, that is to say, a proportion which, if it had been that of vegetables existing before those periods, would always have appeared difficult to reconcile with that elastic and robust organisation which our forest trees require, to raise a firm and secure trunk, and to resist the storms of an atmosphere so agitated as ours. This weak part therefore of the grand problem mnst soon be elucidated, if our cabinets do not delay the eagerness of chemistry to decypher the medals of this kind that they preserve; and if natural history, aided by the lights of analysis, does not succeed in discovering something more satisfactory than any thing that has hitherto been hazarded respecting the origin of pit-coal, we ought to abstain from losing our time in reasoning on this prodigious event in geology, and banish all the learned hypotheses, together with the romances on this subject which our age has produced. I have said that, analysis discovers in these bitumens characters which do not shew a greater affinity to vege tables than animals. The following are the facts. It is however for the learned, who make these things their study, to examine them, and decide on which side the balance inclines. 1. The smell that coals exhale when heated, is aromatic, succinated, and decidedly resinous; it irritates neither the eyes nor the lungs, like that of plants or wood when when burnt; and, indeed, a balsamic property has even been attributed to this resinous smell, favourable to pulmonary diseases. 2. All coals soften, lose their shape, melt and run into the shape of the retort, and fill it with a spungy or puffy coal, like that common to mucous substances, resins, indigo, gluten and animal matters; but never like that of any plant, or of any known wood. 3. Distillation extracts from it a lighter, more aromatic, and more abundant oil, than from the non-resinous woods that are used for fuel; also much water and ammonia; but none of that vinegar which abounds so much in the distillation of our vegetables, that empyreumatic acid which renders their smoke so inconvenient and suffocating; in short, vinegar *, which is formed whenever oxygen is an integrant part of an organic oxyd, and the absence of which in the products of coal authorises us, to a certain degree, to doubt, that oxygen is one of its products. 4. The combustion of coke does not resemble that of our vegetable charcoals; it is slow and difficult like that of mineral coals, because it also contains condensed azot. It also requires to be burnt in a condensed atmosphere. 5. Coke, passed through potash, constantly yields prussic lixivium, which is not usual with vegetable charcoals. 6. Animal charcoal cannot be inflamed by nitric acid, even after it is dis-azotised by potash; neither can coke, even passed through this alkali. * I was in doubt, for some time, whether the pyroligneous acid was really vinegar, as Fourcroy and Vauquelin have asserted; but I have now no hesitation in allowing it, because the salt I formed with oxyd of copper and the acid of elm, displayed its characters after three purifications. It gave large rhombs, differing in no respect from acetate of copper. A mixture A mixture of salt-petre and coke burns with as much difficulty as mixtures of salt-petre and charcoal of blood, white of egg, indigo, &c. 7. There are few kinds of wood that do not leave more ashes than pit-coal. That of Langreo and Villanueva afford but two hundredths; there are some even that do not leave more than one hundredth. Pit-coal, there fore, is not clay mixed with bitumen, as some naturalists have supposed. 8 I have not yet found oxyd of manganese in animal charcoal; and I have also sought for it in vain in the five kinds of pit-coal above-mentioned. 9 Vegetable ashes contain a great deal of carbonate of lime, beside magnesia, clay and silex. Those of the five coals I examined afforded only a great deal of silex, a little magnesia, alumine, and sulphate of lime, but very little carbonate, and particularly not an atom of those salts that, are habitually contained in our vegetable ashes; no phosphate nor sea salt, although the mud of these bi tumens is supposed to have been formed with sea water. 10. All the soft or liquid parts of animals contain sulphur. They cannot be dissolved in potash, without surcharging the solutions with it. Wool cannot be dipped into a bath of litharge and lime without being dyed black by it, owing to the sulphuret of lead that adheres to it. If not any pit-coal be absolutely free from pyrite, is it not because the sulphur and iron, the two habitual elements of animal matters, have withdrawn themselves from the organic substance which is converted into bitumen, to form a separate combination? بار I content myself with bringing together these facts, and I refrain from deducing any consequences from them, beVOL, XII.-SECOND SERIES. K cause they require, first, to be compared with a greater number of coals, in order that it may be ascertained whether they are as general as I think them. But we shall, nevertheless, touch on the other properties which separate still more the analogies supposed to exist between pit-coal and vegetables. If, for example, the carbonaceous principle be an element of their composition, in the same manner, and in the same sense, as it is in our vegetables and animals, we shall show, that it is, however, very feebly combined in them, at least very weakly confined by the hydrogen, nitrogen and oxygen. I might almost say independent of them, since it may be obtained from pit-coal by means that would certainly never succeed with any vegetable or animal productions that we know. TO BE CONCLUDED IN OUR NEXT. On the most sensible Re-actives for Muriatic Acid, Carbonic By Professor Pfaff. From the ANNALES DE CHIMIE. IN the researches on the pretended formation of muriatic acid in water by the influence of the Galvanic pile, it is without doubt of great importance to be acquainted with a re-agent very sensible to this acid, in order to be enabled to discover the first traces of it, and to follow its successive increase. Hitherto we have generally employed a solution of nitrate of silver for this purpose. This reagent is undoubtedly extremely sensible to this acid. Kirwan maintains, that by this means we may even dis cover a portion of it when diluted by 108333 parts of water; yet it is still much surpassed by a solution of mild nitrate of mercury, prepared cold. One part of muriatic acid, or 1.15 of specific gravity, diluted with 70000 parts of water, is feebly announced by a slight opaline bue; when diluted with 80000 times its weight of water, it is concealed from this re-active, as well as all others, except mild nitrate of mercury, which very sensibly troubles the water also weakly acidulated. The sensibility of this re-agent goes so far, that even 300000 of a grain of muriatic acid of 1.15 is announced by a slight thickness in the water, containing this infinitely small quantity. By reflecting on the (I may say) absolute indissolubility of mild muriate of mercury, I have been led to the experiments concerning this re-agent. It is also at the same time the most sensible re-agent for ammoniac. One part of the latter, diluted with 30000 parts of water, is discoverable by a slight blackish yellow shade, by the addition of the solution of nitrate of mercury at the minimum of oxydation. Lime or barytes water is generally regarded as the reagent most sensible to carbonic acid. I have found that the solution of acetate of lead surpasses them.. I was accidentally led to observe this fact; some distilled water that I had kept in a cellar not very deep, and in which there were no other fermented liquors, was rendered very sensibly turbid by the addition of this dissolution. Kirwan has stigmatised the acetite of lead as being deceitful, because its dissolution, principally when a little stale, is sometimes rendered turbid with pure distilled water. But it is not deceitful, for the water is not pure; as it always, when this is the case, contains a little carbonic |