And, finally the results obtained in the analysis of identical samples of wrought-iron by the carbonate (a), and by the acetate method (6), are shown in two columns as under.

The application of the above process to the analysis of steel does not call for any special remark, but when cast-iron containing much silicium is operated upon, it will always be necessary to search for and separate any silica that may be contained in the ultimate product.

XVIII.-Note on Mercury-ethyl.

By E. T. CHAPMAN.

BROMIDE of ethyl may be made to yield mercury-ethyl by the action of dilute sodium-amalgam in the presence of acetic ether, just as the iodide yields it. The reaction takes place equally well with both substances.

The compound was recognised by the action of iodine upon it, and also by converting it into zinc-ethyl by digestion with metallic zinc. This is, I believe, the first instance of an organometallic compound of an alcohol-radical, being produced from any other source than the iodide.

I failed in obtaining zinc-ethyl by the action of metallic zinc on bromide of ethyl. Nevertheless, bromide of zinc is formed and gas cvolved. The presence of mercury greatly facilitates the reaction.

I may also mention that sodium decomposes alcoholic solutions, both of mercury-ethyl and mercury-methyl, liberating mercury. The sodium first floats on the solution, but rapidly becomes amalgamated and sinks to the bottom, evolving much gas during the process, and finally leaving a globule of mercury.

These experiments were made in the Laboratory of the London Institution.

Mean of two experiments-104 and 112.

XIX. A Modification of Berthelot's Experiment for the Formation of Acetylene by imperfect combustion.

By HERBERT MCLEOD.

IN January last* M. Berthelot described an experiment in which he formed acetylene by the combustion, with an insufficient quantity of air, of bodies containing carbon and hydrogen. He found that not only did hydrocarbons produce this result, but that compounds containing oxygen, in addition, such as ether, or chlorine, such as ethylic chloride, gave rise to the formation of considerable quantities of acetylene. An experiment of this kind he describes as follows:-" Let us fill an eprouvette of 300 cubic centimeters' capacity with the gas, or pour into it a few drops of the volatile liquid; and then add a few cubic centimeters of ammoniacal cuprous chloride, inflame the combustible vapour, and incline the eprouvette almost horizontally, causing it to revolve so as to spread the cuprous reagent over the whole interior surface; we see immediately the cuprous acetylide produced. It is generated in contact with the flame, and below, in the form of a characteristic red precipitate.

"The experiment is particularly brilliant with ordinary ether and hydride of amyl. It is a beautiful lecture experiment.

"The quantity of acetylene which manifests itself under these circumstances in the form of acetylide is evidently greater than that which is produced under the influence of heat alone acting upon the same compounds. The quantity of acetylene really produced is besides much superior to that which becomes manifest in the form of acetylide, because the greater part of the acetylene burns almost immediately after being formed, and without coming in contact with the reagent. Also, I think, that it will be possible to deduce from this experiment, conveniently modified, a method of preparation of acetylene more advantageous than those which are known up to the present time." It is the object of this communication to describe such a modification.

It is obvious that the most favourable condition for obtaining an imperfect combustion is when the combustion is, so to speak, inverted, and oxygen is made to burn in an excess of the carboniferous gas or vapour. For this purpose an apparatus was em

* Compt. Rend. lxii, 94.

ployed which had been originally constructed some few years ago for exhibiting the combustion of oxygen in ammonia as an illustration in Dr. Hofmann's course of lectures, and which was used for various similar experiments, such as the combustion of oxygen in hydrogen, of oxygen in coal gas, and of chlorine in hydrogen. The apparatus arranged for the formation of acetylene, is shown in Fig. 1. The experiment is most conclusively performed by burning oxygen in marsh-gas, which is passed from a gas-holder through the tube a into a test tube A. When the air has been expelled, a quantity of solution of cuprous chloride

is poured into the test-tube through the tube b, and subsequently an excess of ammonia, the tube being then closed by a compressioncock. The presence of any acetylene in the gas would here be indicated by the formation of the characteristic red precipitate. The gas then passes into a vertical cylinder B, closed at the lower

extremity by a perforated cork carrying two tubes, one of which is rather wide; this tube is closed with a conical cork, carrying a piece of quill tube, to the top of which a platinum jet is adapted, by rolling a piece of thin platinum foil into the form of a tube of two or three millimetres in diameter, and placing it within the glass tube, and subsequently fusing the glass in contact with the platinum; the lower extremity of the glass tube is connected with a gas-holder containing oxygen. The arrangement of the lower part of this cylinder is shown in Fig. 2. From the cylinder B the gases pass into a small receiver, and from thence into a bottle D, fitted with a cork and tubes, perfectly similar to the fittings of the test-tube A. When the air has been expelled from the whole apparatus, the solutions of cuprous chloride and ammonia are introduced into D through the tube d, which is afterwards closed. To ignite the oxygen in the marsh-gas, the conical cork and jet are removed from the wide tube c, a current of oxygen allowed to pass through the jet, the marsh-gas escaping at c inflamed, the jet passed through the flame, and the

FIG.2

cork rapidly returned to its place. The oxygen then continues burning in the marsh-gas, and in the course of a few seconds, the production of acetylene is indicated by the formation of the red precipitate in the bottle D.

By this process it is easy to obtain from marsh gas about 1.5 grammes of cuprous acetylide in an hour. By employing the gases in larger quantities it will doubtless be possible to increase this amount of product considerably. For the purpose of preparing acetylene, one would, of course, employ ordinary coal gas, perhaps charged with ether vapour, the tube A being dispensed with; and if the oxygen can be replaced by atmospheric air, an experiment which will be tried shortly, the production of this interesting hydrocarbon will become a matter of comparative ease,* and although the gas may not be obtained so rapidly or in such a state of purity as by other methods, yet the simplicity of the process and the ease with which the necessary materials are procured, appear to indicate it as one of the most convenient hitherto suggested. It is quite possible, and even probable, that M. Ber

Since writing the above, it has been found possible to replace the oxygen by atmospheric air, and with satisfactory results.

thelot has already modified his experiment in the manner above described, but as far as I am aware no account of it has yet been published.

XX.-Investigations of the Specific Heat of Solid Bodies.

By HERMANN KOPP.

(Abstract from the Philosophical Transactions for 1865.)

I. Historical Introduction.

1. ABOUT the year 1780 it was distinctly proved that the same weights of different bodies require unequal quantities of heat to raise them through the same temperature, or give out unequal quantities of heat on cooling through the same number of thermometric degrees. It was recognised that for different bodies the unequal quantities of heat, by which the same weights of different bodies are heated through the same range, must be determined as special constants, and considered as characteristic of the individual bodies. This newly discovered property of bodies, Wilke designated as their specific heat, while Crawford described it as the comparative heat, or as the capacity of bodies for heat. I will not enter upon the earliest investigations of Black, Irvine, Crawford, and Wilke, with reference to which it may merely be mentioned that they depend essentially on the thermal action produced when bodies of different temperatures are mixed, and that Irvine appears to have been the first to state definitely and correctly in what manner this thermal action (that is, the temperature resulting from the mixture) depends on the original temperature, the weights, and the specific heats of the bodies used for the mixture. Lavoisier and Laplace soon introduced the use of the icecalorimeter as a method for determining the specific heat of bodies: and J. T. Mayer showed subsequently that this determination can be based on the observation of the times in which different bodies placed under comparable conditions cool to the same extent by radiation. The knowledge of the specific heats of solid and liquid bodies gained during the last century, and in the first sixteen years of the present one, by these various methods, may be left unmentioned. The individual determinations then made were not sufficiently accurate to be compared with the present ones, nor was any general conclusion drawn with reference to the specific heats. of the various bodies.