The Rev. W. Whewell on the mean Level of the Sea Mr. Gulliver's Observations on certain Peculiarities of form in the Blood Corpuscles of the Mammiferous Animals Mr. W. Francis's Examination of a crystallized Nickel Ore 335 Dr. J. Davy's Observations on the aqueous Solution of Car- bonate of Magnesia with excess of Carbonic Acid, and on the Salt which it affords by spontaneous Decomposition... 346 An Abstract of Professor Daniell's Papers on the Electrolysis Address of the General Secretaries of the British Association, Dr. C. Schaf haeutl's Remarks on the Electricity of Steam.... 449 Mr. W. G. Armstrong on the Electricity of Effluent Steam.... 452 Mr. H. L. Pattinson's Further Experiments on the Electricity .. G. B. Airy, Esq., Astronomer Royal, on Professor Challis's Address of the General Secretaries of the British Association, R. I. Murchison, Esq. and Major E. Sabine (concluded).... 482 Mr. Lubbock on the Heat of Vapours and on Astronomical I. Illustrative of Mr. GRIFFITH'S Paper on the Mineral Structure of the South of Ireland. II. Illustrative of Dr. FARADAY'Ss Letter to M. Gay-Lussac, on Magneto- electric Induction *. • This Plate will be given in one of the Number of the next Volume. P. 145, line 17 from the bottom: the following reference ought to have been inserted in this place: "An abstract of Prof. Faraday's Seventeenth Series of Researches in Electricity appeared in vol. xvi. p. 336." P. 370, line 12; p. 372 line 15; and p. 374, line 8 from the bottom, for H. G. ARMSTRONG, read W. G. ARMSTRONG. THE LONDON AND EDINBURGH PHILOSOPHICAL MAGAZINE AND JOURNAL OF SCIENCE. [THIRD SERIES.] JULY 1840. I. On the Iodide of a new Carbo-hydrogen. By JAMES F. W. JOHNSTON, F.R.S.* IF F coal gas be made to pass slowly and for a length of time over pure iodine, the latter substance moistens, and is partly changed into a dark-brown liquid, which effervesces with alkaline carbonates, showing the presence of hydriodic acid. After some hours, colourless prismatic crystals shoot out from the iodine, and clothe the interior of the vessel, and ultimately the whole is changed into a mixture of different compounds forming an olive-coloured substance, partly coating thickly the sides of the vessel, and partly constituting an unctuous mass, with the dark fluid at the bottom. The liquid contains free iodine and hydriodic acid. When washed out from the solid portion by alcohol and neutralized by caustic potash, the solution gives a yellow precipitate, consisting of a mixture of Faraday's iodide of carbo-hydrogen (H2 C2 I)+ and of iodide of formyle (iodoform H C2 13). The solid product being exposed to the air loses its unctuosity. If broken up and examined by the microscope it is seen to consist of a congeries of colourless prisms (H2 C2 I) mixed with another substance, which is amorphous, and of a dark green almost black colour. Alcohol separates the former, or if the mixture be exposed to the air they volatilize, leaving the dark green substance nearly pure. The production of the hydriodic acid and of the iodides of formyle and of carbo-hydrogen is easily understood. Coal gas contains probably more than two equiatomic compounds of carbon and hydrogen; at least two, CH2 and C2 H2, the • Communicated by the Author. [† Mr. Faraday's account of this substance will be found in Phil. Mag. First Series, vol. lix. p. 352. EDIT.] Phil. Mag. S. 3. Vol. 17. No. 107. July 1840. B light carburetted and olefiant gases, are present. The latter would furnish the three compounds obtained in this experiment, as shown by the following formula : 2 2 (C2H2) + 5 I = HI + C2H2 I + C2 HI3 that is to say, one atom of olefiant gas decomposes to form hydriodic acid and formyle, while another unites with iodine* directly. Still this does not represent the action quantitively, since the proportion of the C2H2 I is much greater in actual experiment, and appears also to be variable. Such is the action in close vessels provided only with a small aperture to allow the current of gas to pass out very slowly; but since these three compounds are all volatile, it is easy to understand how only the solid dark green fixed substance should be obtained when the iodine is placed in an open vessel and a current of coal gas is made to stream upon it. In this way it was first obtained by Mr. Kemp of Edinburgh, to whom the discovery of this substance is due, and who several years ago presented me with a specimen prepared by exposing iodine for several days to the action of an open jet of coal gas. I am not aware how far Mr. Kemp has since studied the action in close vessels. I. This substance is of a dark olive green colour, is without taste, emits a slight odour of naphtha, is brittle, and has a density of about 0.95. It is insoluble in water, and in boiling alcohol or æther. Treated with hot nitric acid it becomes yellow and dissolves. With muriatic acid either in the form of gas or of liquid acid, it undergoes no change. Sulphuric acid aided by heat decomposes it. It blackens and gives off iodine vapour and sulphurous acid, leaving undissolved a very bulky charcoal. Dry chlorine slowly changes its colour to a dark brown. If previously moistened with alcohol it becomes • During the combination of chlorine with olefiant gas a portion of muriatic acid is formed, a fact inconsistent with the idea of a direct union of the two substances to form H2 C2 Cl: may not an equivalent proportion of the volatile chloroform be produced, as in the above formula, substituting Cl for 1? Felix d'Arcet (Ann. de Chim. et de Phys., lxvi. p. 108.) has stated, that during this action of chlorine on olefiant gas, a second oily liquid is formed, represented by C4 H, Cl O, to which he gives the name of chloretheral, but which Berzelius with great probability I think, considers to be a compound of the chloride with the oxide of elayle (C2H2 Cl + C2H2O). This explanation of the production of muriatic acid, however, implies that the gases employed are always more or less moist. Regnault accounts for the presence of the acid by representing the oily compound by the rational formula (C2H2Cl + HCl) part of which is decomposed during the process, and HCl evolved. But Löwig and Wiedman have shown that C2H3 (acetyle) does not preexist in the oil, though it may possibly be formed by its decomposition. See Poggendorff's Annalen, xlix. p. 133. |