WANKLYN ON ZINC-METHYL. XN.-On Zinc-methyl.* BY J. A. WANKLYN, F.R.S.E. DEMONSTaATOR OF CHEMISTRY IN THE UEIVERSITY OF EDINBURGH. ZINC-METHYL was discovered rather more than ten years ago by Frankland. It was then obtained nearly pure but in quantity so small that many of its leadiug physical properties including its vapour-density specific gravity and boiling point were not determined. Xore recently the subject has again been taken up by the same chemist who this time operated upon several pouuds of materials and under conditions widely differing from those of his former experiments. * An abstract of this paper waa read before the Royal Society of Edinburgh April Znd 1860. WANKLYN ON ZINC-METHYL. The latter investigstion has however not been so successfult as the former inasmuch as it has given no piire zinc-methyl having instead disclosed peculiar and unlooked-for difficulties in the preparation of th3t compound.When zinc and iodide of methyl are heated together in closed tubes the following reactions take place :-(1) . Zn + C2H$ = ZnI.ZnC,H (2) . Zn + ZC2H,T= 2ZnI + C,H,.C,H,. At moderate temperatures the former rcaction predominates ; at higher temperatures the latter. When only iodide of methyl and zinc are employed and no ether is used it is imporsible to obtain complete decomposition of the iodide without at the same time obtaining much gas. This circumstance renders it imprac-ticable to prepare much zinc-methyl by this method as the high pressure of the generated gas necessitates the employment of very small tubes.The copper digester which Frank land emplop for the manufacture of this class of siibstances cannot be made to replace the small glass tubes. Frankland has found that when the materials are heated in the copper digester no pure zinc-methyl can be obtained. A mixtiire of ether with iodide of methyl is easily converted into iodide of zinc and ethereal solution of zinc-methyl. Here however a fresh difficulty arises. Fractional distillation does not avail to separate ether from zinc-methyl. And so pertinaciously do these two liquids cling to oiie another that it is even a matter of doubt whether a chemical compound does not exist between them. To this point our knowledge was advanced by the publication of Frankland's paper" last year.My attention was drawn to this subject in the course of my investigation of the compounds formed by methyl with the alkali-metals. These compounds are prepared by acting upon zinc-methyl with the alliali-metals. At first I employed the solution of zinc-methyl in ether but I found the ether to be a very troublesome complication and therefore was led to enquire whether it were really impossible to obtain zinc-methyl in a state of purity and at the same time in considerable quantity. 'Ann. Ch. Pharm. cxi. 62; also Bakerian Lecture 1859. 126 WANKLYN ON ZISC-3lETHYL. During my experiments I observed the fact that a strong ethereal solution of zinc-methyl equally with ether renders the decomposition of iodide of methyl by zinc easy and comparatively unaccompanied by the cirolution of free methyl.Thereupon I tried a stronger solution of zinc-methyl and found it also effectual. A still stronger solution was also successful and it seemed that even pure zinc-methyl itself possesved the same property. Here then was an available method of making pure zinc-methyl. Strong ethereal solution of that compound was first prepared. The strong ethereal solution was next mixed with iodide of methyl and sealed up with zinc; then after digestion in the water-bath distilled. In this manner a stronger solution of ziiic-methyl was prepared. By repeating the process a sufficient number of times the amount of ether originally taken was made to bear a very trifling ratio to the ultimate product; and indeed could be made to vanish altogether.In evidence of the practicability of the plan just proposed I may mention that the product from a single tube which had undergone four successive digestions amounted to about half an ounce and proved to be zinc-methyl as pure as the gramme or two obtained by Frankland ten years ago. Before giving the analysis of this sample I will just men-tion it few particulars cennected with its preparation which may be interesting to any one who may desire to prepare the compound. The digestions were ail made in the water-bath the substance being always contained in glass tubes. In order that an ounce or two of iodide of methyl might be with safety heated in a single tube the precaution mas taken of opening the tube several times in the course of the digestion.By this means a dangerous accumulation of hydro-carbon gas was avoided. The distillation of the zinc-methyl was made over the naked flame. Finally previously to the last distillation a digestion with metallic-zinc without any fresh iodide of methyl was made. I map aiso mention that iodide of zinc forms with zinc-methyl a crpstalline compound of great beauty and very different in appearance from the crystalline compound between iodide of zinc and zinc-ethyl. This compound containing probably one equivalent of zinc-methyl corn bined with one equivalent of iodide of zinc I regard as the repiesentative of the so-called iodide of mercury-methyl obtained by Fran kl an d.WANKLYN ON ZINC-METHYL. Double zinc compound. Double mercury compound Passing on to the properties of the half-oiince of zinc-methyl whose preparatiori I have just described :-It mas highly inflam- mable and acted upon water with explosive violence agreeing with Franliland's description of that compound. In one particular however our observations do not accord with one another. The poisonous nature of the fumes their action upon the nervous system which Frankland mentions," I have not been able to verify. I have distilled zinc-methyl more than a dozen times and been much exposed to its fumes and still have not been able to mark any particular effect upon myself. In addition to the properties detailed by Frankland I have to record that sinc-methyl in a state of purity is very per- manent.If carefully excluded from the atmosphere it will bear without decomposition a temperature of at least 200"C. r At about 270" C. it begins to be reduced to metallic zinc and hydro-carbon gases. I have made an analysis of the sample of zinc-methyl with the following results :-I. 01134 grm. of the liquid were passed up into a graduated tube standing in the pneumatic trough and filled with water. Hydride of methyl was evolved measuring 48*77 cubic-centimeters (dry) at 760 m.113 pressure and O'C. This equals 0034898grm. by weight :-Hydride of methyl per cent. =30*77 11. -1172 grm. similarly treated gave -0361 grm. of hydride of methyl or 30.83 per cent. The theoretical percentage of hydride of methyl which pure zinc-methyl should give on treatment with water equals 33.51.These results do not depart from the theoretical quantity firther than that which Frankland published ten years ago. His percentage of hydride of methyl was 29.91. In estimating the value of these determinations it should be borne in mind that the quantity of hydride of methyl obtained represents its equivalent of unoxidized zinc-methyl. The slightest oxidation tells enormously upon the analysis; for not only does * -4nn. Ch. Pharm. lxxi. page 214. WANKLYN ON ZINC-METILYL. the oxygen lower the percentage of methyl by its presence but by combining with a certain amount of zinc-methyl it still further lowers the percentage of methyl which can clecoinpose water.The great violence of the reaction between zinc-methyl and water is also a source of loss especially %hen water and not mercury is the confining fluid as was the case in both Frankland's analysis and my own. A determination of' the vapour-density by Gay Lussac's method was also made. 01163 grm. of zinc-methyl were employed. The temperature to which the vapour was exposed was 100"C ; the boil- ing point of the compound lying between 50" C and 60' C. The ex- periment gave 3.291 as the vapour density of zinc-methyl. If as seems likely the condensation of this compound is analogous to that of its ethyl representative the theoretical vapour-density is 3.299 a number which is nearly identical with that found by experiment.The accurate determination of its boiling point and also of the specific gravity in the liquid state I hope shortly to have an opportunity of making as I expect at no very distant period to be in possession of several ounces of pure zinc-methyl. I cannot conclude this paper without calling attention to the very remarkable state of condensation disclosed by examination of the vapour-densities of zinc-ethyl zinc-methyl mercury-ethyl mercury-methyl and indeed of all the so-called organo-metallic bodies so far as has yet been investigated. It has been said the metals are the strict representatives of hydrogen; and yet in not a single compound of a metal with a hydro-carbon radical Tias the metal been found in the state of condensation of hydrogen.If we write the formuh of equal volumes of several of these bodies we arrive at the following expressions :-Zinc-methyl. Zinc-ethyl. Mercury-methyl Mercury-ethyl Distann-methyl. Distann-e thy1 . Writing also the formuh of equal volumes of the fiydrogen alld oxygen terms for comparison with the former :- GGTHRIE ON SOME DERIVATIVES FRON TBE OLEFINES 129 Hydride of methyl. Hydride of ethyl. Methyl-ether. Ethyl-ether. Inspection of the above shows that considered as to the state of condensation in their hydro-carbon compounds the metals do not represent hydrogen mercury and zinc represent oxygen. Nor is this peculiarity confined to the organic case. Deville and others have recently taken the vapour-density of various metallic chlorides and have found that these likewise are present in a more condensed form than their hydrogen representative. Whereas the formula of hydrochloric acid is ,the formula of an equal volume of metallic chlqride is