The trichloride is extremely hygroscopic, deliquescing on exposure to air to a brown liquid. The trichloride is best prepared by the quick decomposition of the tetrachloride at its boiling point, or by its slow decomposition at the ordinary temperature of the air. The crystalline powder obtained by either of these methods only requires freeing from adhering tetrachloride by drying in carbon dioxide at 160° in order to yield good analytical results. Mean of 4 analyses. Calculated. V = 51.3 32.57 The trichloride thrown into water does not at once dissolve; but, as soon as the crystals get moistened, a brown solution is formed, which becomes green on addition of a drop of hydrochloric acid, and contains a hypovanadic salt in solution. This green tint is identical with that got by reducing a solution of vanadic acid in presence of magnesium. According to the equation 2VCI,+02+3H20=V2O,+6HCl the solution of the trichloride requires 10-14 per cent. of oxygen to bring it up to vanadic acid, whilst analysis showed that 10.1 per cent. was necessary. The specific gravity of the trichloride at 18° is 3.00. 3. Vanadium Dichloride VCl,=122.3.-The dichloride is a solid crystallizing in fine bright apple-green micacious plates. It is prepared by passing the vapour of vanadium tetrachloride mixed with hydrogen through a glass tube heated to dull redness. If the heat be pushed further a blackish crystalline powder, consisting of a mixture of lower chloride and metal, is obtained. The dichloride, when strongly heated in hydrogen, loses all its chlorine, leaving vanadium in the metallic state in grey crystalline grains. Analysis gave : Vanadium dichloride is extremely hygroscopic; when thrown into water a violet-coloured solution is formed, identical in tint with the liquid containing a hypovanadous salt obtained by reducing vanadic acid in solution in presence of zinc- or sodium-amalgam; and like this latter liquid, the solution of dichloride in water bleaches strongly by reduction. Oxidized by permanganate this liquid required 18.78 per cent. of oxygen (on the dichloride taken) to bring it up to vanadic acid, whereas the equation 2VCl,+O,+2H2O=V2O,+4HCl requires 19.6 per cent. The specific gravity of vanadium dichloride at 18° is 3.23. Metallic Vanadium V=51·3.—Although from what we now know of the characters of vanadium it appeared unlikely that any compound con taining oxygen would yield the metal by direct reduction, the author has repeated the experiments of other chemists on this subject, but without success. There is no doubt that the metal cannot be obtained by any of the processes described in the books. The only methods which promised possible results were :— 1. The reduction of a vanadium chloride (free from oxygen) in hydrogen gas, either with or without sodium. 2. The reduction of the mononitride at a white heat in hydrogen. The first of these methods has proved to be successful, whilst the second does not appear to yield metal, inasmuch as the nitride exposed for 3 hours in a platinum tube to the action of hydrogen at a white heat, lost only 8 per cent., whereas it must lose 21.4 per cent. on conversion into metal. Notwithstanding the apparent simplicity of the method, the author has found it exceedingly difficult to obtain the metal perfectly free from oxygen. This arises from the fact that whilst vanadium is quite stable at the ordinary temperature, it absorbs oxygen with the greatest avidity at a red heat, and that therefore every trace of air and moisture must be excluded during the reduction. Another difficulty consists in the preparation of the solid chlorides in large quantity and free from oxygen or moisture, as also in the length of time needed to reduce these chlorides in hydogen, during which time unavoidable diffusion occurs and traces of oxygen enter the tube. Again, the reduction can only be effected in platinum boats placed in a porcelain tube, as the metal acts violently on glass and porcelain, and tubes of platinum are porous at a red heat. A description of the apparatus employed is then given, the main points being to guard against diffusion, and to introduce the powdered dichloride into the platinum boat in such a way that it shall not for an instant be exposed to moist air. After all precautions are taken the tube is heated to redness, torrents of hydrochloric acid come off, and the evolution of this gas continues for from 40 to 80 hours, according to the quantity of dichloride taken. After the evolution of any trace of hydrochloric acid has ceased to be perceptible, the tube is allowed to cool, and the boat is found to contain a light whitish grey-coloured powder, perfectly free from chlorine. Metallic vanadium thus prepared examined under the microscope reflects light powerfully, and is seen to consist of a brilliant shining crystalline metallic mass possessing a bright silver-white lustre. Vanadium does not oxidize or even tarnish in the air at the ordinary temperature; nor does it absorb oxygen when heated in the air to 100°. It does not decompose water even at 100°, and may be moistened with water and dried in vacuo without gaining weight. The metal is not fusible or volatile at a bright red heat in hydrogen; the powdered metal thrown into a flame burns with the most brilliant scintillations. Heated quickly in oxygen it burns vividly, forming the pentoxide; but slowly ignited in air it first glows to form a brown oxide (possibly V2O), and then again ab sorbs oxygen and glows with formation of the black trioxide and blue tetroxide till it at last attains its maximum degree of oxidation. The specific gravity of metallic vanadium at 15° is 5.5. It is not soluble in either hot or cold hydrochloric acid; strong sulphuric acid dissolves it on heating, giving a yellow solution; hydrofluoric acid dissolves it slowly with evolution of hydrogen; nitric acid of all strengths acts violently on the metal, evolving red nitrous fumes and yielding a blue solution; fused with sodium hydroxide the metal dissolves with evolution of hydrogen, a vanadate being formed. One sample yielded on oxidation a percentage increase of 77.94, whereas that calculated from metal to pentoxide is 77.98. Another preparation gave a percentage increase of 70 8, showing the presence of a small quantity of oxide. On treatment in a current of chlorine metallic vanadium burns and forms the reddish black tetrachloride; heated in a current of pure nitrogen the mononitride is formed. The properties of the compounds of vanadium with silicon and platinum are then described in the memoir. XX. "On Palæocoryne, a genus of the Tubularine Hydrozoa from the Carboniferous formation." By Dr. G. MARTIN DUNCAN, F.R.S., Sec. Geol. Soc., and H. M. JENKINS, Esq., F.G.S. Received June 14, 1869. (Abstract.) Palæocoryne is a new genus containing two species, and belongs to a new family of the Tubularidæ. The forms described were discovered in the lower shales of the Ayrshire and Lanarkshire coal-field, and an examination of their structure determined them to belong to the Hydrozoa, and to be parasitic upon Fenestellæ. The genus has some characters in common with Bimeria (St. Wright), and the polypary is hard and ornamented. The discovery of the trophosome, and probably part of the gonosome of a tubularine Hydrozoon in the Paleozoic strata brings the order into geological relation with the doubtful Sertularian Graptolites of the Silurian formation, and with the rare medusoids of the Solenhofen stones. XXI. BAKERIAN LECTURE.-"On the Continuity of the Gaseous and Liquid States of Matter." By THOMAS ANDREWS, M.D., F.R.S., &c. Received June 14, 1869. (Abstract.) In 1863 the author announced, in a communication which Dr. Miller had the kindness to publish in the third edition of his 'Chemical Physics,' that on partially liquefying carbonic acid by pressure, and gradually raising at the same time the temperature to about 88° Fahr., the surface of de marcation between the liquid and gas became fainter, lost its curvature, and at last disappeared, the tube being then filled with a fluid which, from its optical and other properties, appeared to be perfectly homogeneous. The present paper contains the results of an investigation of this sabject, which has occupied the author for several years. The temperature at which carbonic acid ceases to liquefy by pressure he designates the critical point, and he finds it to be 30°-92 C. Although liquefaction does not occur at temperatures a little above this point, a very great change of density is produced by slight alterations of pressure, and the flickering movements, also described in 1863, come conspicuously into view. In this communication, the combined effects of heat and pressure upon carbonic acid at temperatures varying from 13° C. to 48° C., and at pressures ranging from 48 to 109 atmospheres, are fully examined. At131 C., and under a pressure, as indicated approximately by the air manometer, of 48 89 atmospheres, carbonic acid, now just on the point of liquefying, is reduced to of the volume it occupied under one atmosphere. A slight increase of pressure, amounting to of an atmosphere, which has to be applied to condense the first half of the liquid, is shown to arise from the presence of a trace of air ( part) in the carbonic acid. After liquefaction, the volume of the carbonic acid, already reduced to about of its original volume, continues to diminish as the pressure augments, and at a much greater rate than in the case of ordinary liquids. Similar results were obtained at the temperature of 21.5. A third series of experiments was made at 31°·1, or 0°-2 above the critical point. In this case the volume of the carbonic acid diminished steadily with the pressure, till about 74 atmospheres were attained. After this, a rapid but not (as in the case of liquefaction) abrupt fall occurred, and the volume was diminished to one-half by an additional pressure of less than two atmospheres. Under a pressure of 75·4 atmospheres, the carbonic acid was reduced to of its original volume under one atmosphere. Beyond this point it yielded very slowly to pressure. During the stage of rapid contraction there was no evidence at any time of liquefaction having occurred, or of two conditions of matter being present in the tube. Two other series of experiments were made, one at 32°.5, the other at 35°5, with the same general results, except that the rapid fall became less marked as the temperature was higher. The experiments at 35°.5 were carried as far as 107 atmospheres, at which pressure the volume of carbonic acid was almost the same as that which it should have occupied if it had been derived directly from liquid carbonic acid, according to the law of the expansion of that body for heat. The last series of experiments was made at 48° 1, and extended from 62.6 to 109.4 atmospheres of pressure. The results are very interesting, inasmuch as the rapid fall exhibited at lower temperatures has almost, if not altogether, disappeared, and the curve representing the changes of volume approximates closely to that of a gas following the law of Mariotte. The diminution of volume is at the same time much greater than if that law held good. The results just described are represented in a graphical form in the figure given below. Equal volumes of air and carbonic acid, measured at CURVES 100 915 AIR CARBONIC ACID 4891 0° C. and 760 millimetres, when compressed at the temperatures marked on each curve, undergo the changes of volume indicated by the form of the curve. The figures at the top and bottom indicate the approximate pres CURVES 18.1 50ATM 55▬▬60—65 |