The vaporization of red phosphorus is exceedingly slow as compared with that of a liquid body. An exhausted glass tube containing red phosphorus was screwed up in an iron one, the interstices being filled with magnesia pressed down. The tube was then heated in the flame of five Bunsen's burners, the temperature of which was gradually raised. In the cases in which the tubes held out, besides the drops of colourless phosphorus, the red phosphorus was found to be merely sintered together, and not melted. In this respect, as comparative experiments showed, the deportment of phosphorus quite resembles that of arsenic: arsenic heated in a closed tube volatilized and formed beautiful crystals without melting. Colourless phosphorus, when heated in an hermetically sealed vessel (an iron tube can be used), is changed into red phosphorus by being heated for a short time to a temperature of 300° C. An attempt was made to determine directly the heat which becomes free when colourless changes into red phosphorus, by placing a thermometer in some phosphorus contained in a flask which was heated in an air-bath. When the temperature of the bath was 295°, the thermometer in the phosphorus marked 282°; at this point the temperature of the latter began rapidly to rise and soon attained 370° C.; the cork in which the thermometer was placed was not tight at this temperature, and phosphorus-vapours escaped and caused the experiment to be stopped. Schrötter found the tension of colourless phosphorus to be 760 millims. at 290°; comparing this with that of red, which at 358° is only 31 millims., and considering that above 300° liquid colourless phosphorus cannot exist, it would appear possible to drive phosphorus from a position of lower temperature to one of higher. An exhausted tube containing ordinary phosphorus was exposed at one end to the temperature 255°, and at the other to that of 358° C.; the hotter part remained, however, quite empty; no red phosphorus was deposited there. It follows from this that colourless phosphorus-vapour can retain a highertension and density than that which is formed from red phosphorus. A number of special experiments show that when colourless phosphorus was used instead of red, far higher densities and tensions were obtained for the same temperatures. Colourless phosphorus in the exhausted tubes, when the temperature is raised, has probably passed partially into the vaporous state. The part which has remained liquid passes into the state of red phosphorus, and, by its disengagement of heat, materially increases the temperature of the surrounding medium, and thus gives a higher density and tension to the vapour. Experiment showed that the tension and density which the vapours at first obtain are not stable and continually diminish, while red phos phorus is deposited. Only after about two hours' heating is a stable maximum obtained; it very slowly increases with the temperature, and is always considerably greater than that disengaged at the same temperature from red phosphorus. A large quantity of colourless phosphorus was heated in hydrogen gas under various pressures, which increased to four atmospheres. When heated over free flame it always boiled rapidly ; the formation of vapour was always more rapid than the change into red phosphorus. From Hittorf's experiments it follows that the vapour of red phosphorus may be cooled from 417° to 358° (that is, through 90°) without changing its condition. This was confirmed by the fact, that in an exhausted tube one end of which was heated to 358° and the other, which contained red phosphorus, to 4470, no deposit of phosphorus was observed in the first. In order to observe the pressures directly, phosphorus was placed in the closed end of an exhausted siphon-barometer the bend of which was closed by bismuth; this metal does not combine with phosphorus at 447°, and only absorbs its vapour to a small extent. The open leg was filled with hydrogen and was connected with a manometer, so that, by disengagement of hydrogen and pressure of mercury, pressure could be exerted on the bismuth. When the siphon part was heated to 447°, the phosphorus-vapour had a pressure of 1 atmosphere, much less, therefore, than 1633 millims., which the first experiments gave; the difference arises from the absorption of phosphorus by the bismuth. It could, however, be shown that, spite of the fact that the formation of vapour had ceased, the vapour had not the density which it could possess at this temperature; for the pressure of the hydrogen could be raised to 3 atmospheres before the short leg was completely filled with bismuth. If the pressure was again diminished, a perceptible and very slow formation of vapour ensued under a pressure of 14 atmosphere. If an exhausted tube containing red phosphorus be heated in one part to 530°, and in another to 447°, microscopic needles are deposited in the cooler part. These crystals were obtained of a larger size by taking advantage of the property which lead has of dissolving phosphorus at high temperatures and depositing it on cooling. Colourless phosphorus was placed with lead in a strong hard glass tube, which was exhausted of air and then sealed. This tube was placed in an iron one which had screw plates at each end, the interstices being filled with magnesia, and the whole heated in the flame of five Bunsen's burners for 8 or 10 hours. The phosphorus was obtained on the surface of the lead as striated prismatic lamina several lines in length and bent like and red in transmitted light, and unalterable in the air. The lead becomes much less fusible, and that which has been already used is more suited for the formation of crystals on its surface. The lead contains crystals dissolved which are not detected on cutting it, but may be obtained on dissolving the lead by the prolonged action of cold nitric acid of 11 spec. grav. The crystals thus obtained appear to be rhombohedra, and are thus probably isomorphous with the crystals of As, Sb, and Bi. There is then a metallic phosphorus which is amorphous in Schrötter's modification and crystallized in this new form, and a non-metallic form-that originally discovered by Brandt. The new metallic phosphorus has the spec. grav. 2.34 at 15°5 C.; and its atomic =33 13.25, is identical with that of metallic arsenic. Amorphous phosphorus, when heated for a long time, passes into the crystalline modification. 31 volume, 2.31 Crystallized phosphorus is less volatile even than amorphous. It forms no colourless phosphorus below 358°. The maximum tension and vapour-density are at all temperatures far lower than those of amorphous phosphorus. Thus at 447° a litre of the vapour weighs 2.573 grms. and has the tension 928 millims. At 530° the weight is 10-198 to 10.338 grms., and the tension 4101 to 4158 millims. The author points out that phosphorus is probably the first body which has a different tension in its different modifications. He shows, too, that the vapour of colourless phosphorus retains its density and tension unaltered even if in contact with the amorphous metallic phosphorus. Hittorf states that Geissler, by placing colourless phosphorusvapour in closed glass tubes, has changed it into red by passing the electric spark through it while in the state of vapour. The author shows that sunlight does not change the vapour, nor does the electric light. Yet a white heat effects the change to a small extent, as is seen when phosphorus-vapour is driven through a white-hot porcelain tube by means of a current of hydrogen. The same effect is produced if charcoal-points placed in the vapour are raised to incandescence by the electric current. XLVII. Proceedings of Learned Societies. CAMBRIDGE PHILOSOPHICAL SOCIETY. [Continued from p. 233.] N the Papyrus of the Lake of Gennesaret." By The author pointed out the distinctions between Cyperus papyrus and Cyperus syriacus. The former, the papyrus of history, grows in Nubia and on the White Nile, and was found (by Rev. II. B. Tristram) on the shores of the Lake of Gennesaret, and in a large bog near Lake Hûleh. The latter grows in Sicily and on the Syrian coast: this is the plant cultivated in storehouses in England. "On a Specimen of Echinarachnius Woodii, from the Coralline Crag." By Professor Liveing. The author exhibited a very perfect specimen from near Aldborough. He explained his reasons for differing from the late Professor Edward Forbes, who had named and described the fossil from two imperfect specimens; and he assigned it to the genus Rhynchopygus. "On a New Theory of the Skull and of the Skeleton; with a Catalogue of the Fossil Remains of Vertebrate Animals contained in the Woodwardian Museum." By Mr. Harry Seeley. The author endeavoured to prove that growth in bone was the result of forces acting upon it; so that the stimulants of growth were pressure and tension. He argued against the theory which considered the skull to be a development of three vertebræ, and pointed out analogies between the several parts of the skull and the epiphyses and centrum of a vertebra. He considered the brain-region o be a modified vertebra, and the bones about the breathing apertures the modified end of the trachea. March 12.-" On the Homeric Tumuli." By Mr. Paley. The author described the funeral rites of the Greeks and Trojans as narrated in the Homeric Poems, and explained the mode in which the tumuli were constructed-pointing out resemblances between these descriptions and the tumuli which have been examined in various parts of Europe. "On the Method of demonstrating some Propositions in Dynamics." By Mr. Todhunter. ROYAL SOCIETY. [Continued from p. 237.] February 1, 1866.-Lieut-General Sabine, President, in the Chair. The following communications were read : "On the Specific Gravity of Mercury." By Balfour Stewart, M.A., LL.D., F.R.S., Superintendent of the Kew Observatory. Some time since, in connexion with a research on the fusingpoint of mercury, several observations were made at Kew of the specific gravity of this fluid. A specific-gravity bottle was used for this purpose, and it was washed, in the first place with sulphuric acid, secondly with distilled water, and thirdly with alcohol; when this was done it was found to contain mercury without any air-specks or any diminution of that metallic lustre which pure mercury exhibits when in contact with a vessel of clean glass. Three different specimens of pure mercury were used, and were separately weighed in the specific-gravity Mercury from the cistern of the old Kew Mercury from the cistern of the new Kew the mean of these will be 13591.66 grs. Weighed in air. grs. 13591.36 13591.66 13591.96 It was found that the specific-gravity bottle had an internal volume equal very nearly to 4 cubic inches; and assuming that a cubic inch of air weighs 0.31 gr., then the air displaced by the liquid filling the bottle would weigh 1.24 gr. In like manner the air displaced by the Kew standard weights (sp. gr. 8.2) would have the volume of 6.6 cubic inches, and would weigh 2.04 grs. From these premises we find that the real weight of the mercury in vacuo would have been 13590·86 grs. Again, the amount of water which the same bottle held at 62° F. weighed in air 1000·53 grs. Here the air displaced by the bottle is, as before, 1.24 gr., while that displaced by the weights is only 0.15 gr. From this we find that the real weight of water filling the bottle at 62° F. would be in vacuo 1001.62 grs. We have thus grs. True weight of mercury filling the bottle at 62° F. = 13590.86 True weight of the same volume of water at 62° F. = 1001·62 And hence the specific gravity of mercury at 62° F., as compared with water at the same temperature, will be 13.569 nearly. Again, if we assume the correctness of Regnault's Table of the absolute dilatation of mercury, and also that of Despretz's Table of the absolute dilatation of water, we shall find that the weight at 32° F. of a volume of mercury weighing 13590·86 grs. at 62° F. will be 13590.86 × 1.00298=13631·361 grs. Also the volume at 4° C., or 39°.2 F., of a volume of water weighing at 62° F. 1001.62 grs., will be 1001.62 × 1.0011437 1002 766 grs. Hence the specific gravity of mercury, according to the French method of determining it, will be A determination by Regnault gives 13.596. These two results agree very nearly with one another; and this agreement tends not only to verify the correctness of Regnault's determination, but to show that Regnault's Table of the dilatation of mercury, and Despretz's Table of the dilatation of water, agree together-a remark that had been previously made by Dr. Matthiessen in a paper which he recently presented to the Society. |