haloid with granulated zinc or zinc filings in presence of a small quantity of iodine, the apparatus employed resembling that next described. The organo-zinc compounds are also obtained by employment of an alloy of zinc and sodium. To prepare this, zinc is heated in a Hessian crucible until it volatilises freely, and one-fourth of its weight of sodium stirred in. After the combination of the metals the crucible is removed from the fire, filled with dry sand to prevent contact with air, and then cooled. When cold, the crucible is broken, and any sodium adhering to the regulus cut off, and the last traces removed by treatment with water. The well-dried metallic mass is then coarsely powdered and preserved in well-stoppered glass vessels. The alloy is placed in the flask A (fig. 19), heated by a water bath, and warmed for a long time with an equal weight of the alkylic iodide. The flask is connected with an inverted condenser B, in which the evolved vapours are condensed and flow back into the flask. The condenser tube has at its upper end a small set of bulbs c, in whose bend a small quantity of mercury prevents access of air whilst allowing the escape of any gas evolved. Previous to heating the ingredients the whole apparatus is filled with carbonic anhydride by means of the tapped tube a, and the tap then closed. After completion of the reaction the flask is connected with a condenser placed in the usual way, whose lower end is connected with a receiver provided with a mercury valve similar to that above described. The zinc compound in the flask formed according to the equation: ZnNa2+ 2ICnH2n+1 = 2NaI + Zn(CnH2n+1)2, is then distilled, a current of dry carbonic anhydride passing through the tube a. Finally, the organo-zinc compounds are obtained by heating the corresponding mercury compounds with zinc filings to 100°-130°. The separated mercury amalgamates with the excess of zinc : Hg(CnH2n+1)2 + Zn2 = HgZn + Zn(CnH2n+1)2. The product is then distilled in a stream of carbonic anhydride. 366. The zinc organo compounds are colourless, peculiarly smelling bodies, which oxidise in air with evolution of fumes and mostly with spontaneous inflammation. They burn with a bluish green flame and formation of thick fumes of zincic oxide. If the oxidation be moderated by allowing the ethereal solutions to remain in imperfectly closed vessels, two oxidation products are formed by the oxygen atoms placing themselves between the zinc and the alcohol radical—namely, first according to the equation: 2Zn CnH2n+1 and on further oxidation : The latter compounds decompose on contact with water into alcohols and zincic hydrate : Zn(O.CnH2n+1)2 + 2H2O = Zn(OH)2 + 2HO.C2H2n+1 The unoxidised compounds also react on water with explosive violence, yielding paraffins (hydrides of the alcohol radicals) (§ 149) : Zn(CnH2n+1)2 + 2HOH = Zn(OH)2 + 2CnH2n+2° Like oxygen, sulphur unites directly with them, forming zinc mercaptides: Zn CnH2n+1 +2S Zn< S.CnH2n+1 With the haloid compounds of the alcohol radicals they give, especially on heating, zinc haloids and paraffins (di-radicals) (§ 150): = CnH2n+1 Zn(CnH2n+1)2 + 2CnH2n+1I ZnI2+ 2 | CnH2n+1 Free halogens yield, by a very violent reaction, zinc haloids and alkylic haloids : Zn(CnH2n+1)2 + 2Br2 = ZnBr2+2CnH2n+1Br. Their employment in the preparation of tertiary phosphines (§ 297) of organo-metallic bodies, and of tertiary alcohols (§ 163), has already been mentioned. Ethereal solutions of these zinc compounds absorb sulphurous anhydride and nitric oxide gases with formation of crystalline salts of peculiar acids, of which the sulphur acids have already (§ 252) been noticed. CH3' 367. Zinc methyl, zinc dimethyl, Zn<CH3, is usually prepared by heating mercury dimethyl with zinc, further by heating methylic iodide with zinc-sodium alloy or with powdered zinc in sealed glass tubes at 100°. It is a colourless, strongly refractive, extremely unpleasant smelling liquid, of sp. gr. 1.386 at 10.5°, which boils at 46°. Mixed with ethylic ether, it yields between 51° and 57° a liquid which cannot be separated by fractional distillation and whose proportional composition is represented by the formula 2Zn(CH3)2,(C2H5)2O. On addition of some methylic alcohol to zinc methyl there is formed, according to the equation Zinc methyl-methylate as a white, spongy, somewhat crystalline If excess of methylic alcohol be employed, solid zinc dimethylate is obtained. Zinc methyl inflames in air. mass. 368. Zinc ethyl, zinc diethyl, Zn(C2H3)2, completely resembles the methyl compound, has sp. gr. 1182, boils at 118°, and has a vapour density of 4.26. In ethereal solution it absorbs two molecules of nitric oxide gas, and yields large colourless crystals, in which onehalf of the ethyl is still united with zinc: Zn(C2H5)2 + N2O2 = C2H5.N2O2.(ZnC2H5). The action of water causes ethane to be evolved, whilst the basic zinc salt of dinitro-ethylic acid results: C2H5N2O2(ZnC2H5) + H2O = C2H6 + C2H¿N2O2(Zn.OH), from whose solution one-half of the zinc can be precipitated by means of carbonic anhydride : 2C,H5.N2O2.Zn.OH + CO2 = ZnCO3 + H2O + (C2H¿N2O2)1⁄2Zn. From the soluble neutral zinc salt, other salts of dinitro-ethylic acid can be prepared by double decomposition : (C2H,N2O2)2Zn + Na2CO3 = ZnCO, + 2C2H ̧N202.Na. They are all difficultly crystallisable, and when heated in the dry state explode violently. By treatment of dinitro-ethylic acid or its salt with nascent hydrogen, equal molecules of ethylamine and ammonia are obtained: 2 C2H ̧N2O2H + 8H = C2H5.NH2 + NH3 + 2H2O. Therefore the constitution of the acid is best expressed by the formula: C,H,.N-O-N.OH or C2H,.Ñ—N.OH. 369. Zinc dipropyl, Zn(CH2.CH2.CH3)2, boils at 146° and is spontaneously inflammable. Zinc diisobutyl, Zn(CH)2, boils between 185° and 188°. Zinc diisoamyl, Zn(C,H11)2, is liquid, has sp. gr. 1022, boils at 220°, and fumes in the air without inflaming spontaneously. OTHER METALLIC COMPOUNDS OF THE ALCOHOL RADIcals. 370. Magnesium diethyl, Mg.(C2H5)2, is obtained as a volatile liquid, smelling like garlic, when magnesium filings are digested with ethylic iodide in absence of air. There is first formed solid magnesium ethyl iodide : 2 H5 Mg + C2H2I = Mg C2H2 I which on strong heating in vessels filled with carbonic anhydride leaves a residue of magnesic iodide, whilst liquid magnesium diethyl distils over. Magnesium diethyl inflames spontaneously in air, and is decomposed with explosive violence by water into magnesic hydrate and ethane. Magnesium dimethyl is entirely similar in preparation and properties. 371. Compounds of the alkali metals with the alcohol radicals cannot be obtained in the isolated state; they are undoubtedly formed by the action of sodium or potassium on organo-zinc compounds, zinc being separated even at ordinary temperatures: Zn(C2H5)2 + Na2 = Zn + 2NaC2H5. The resulting liquid crystallises at low temperatures, but invariably contains much unaltered zinc compound, and is at once converted by water into ethane, zincic hydrate, and sodic hydrate: NaC2H5 + H2O = NaOH + C2H ̧· Sodium ethyl, when mixed with ethylic iodide, yields sodic iodide at ordinary temperatures, but does not give diethyl (butane), but a mixture of ethylene and ethane : NaC2H+IC2H5 NaI + C2H6 + C2H ̧· 372. Compounds of thallium and tungsten with ethyl are also known, but the metals are not united by all their bonds to ethyl, but in part also to negative elements. Amongst such bodies are chloride, nitrate, and sulphate of the strongly positive monacid radical thallium diethyl, TI(C2H5)2C1, Tl(C2H5)2.Ö.NO2, [TI(C2H5)2]2SO4, &c. Tungsten gives with methylic iodide tungsten trimethyl iodide, W(CH3)3Ï, crystallising in colourless tables. DISUBSTITUTION PRODUCTS OF THE PARAFFINS. DERIVATIVES OF THE DIAD RADICALS, CnH2n 373. The replacement of two of the hydrogen atoms of a paraffin by other elements yields compounds of the diad hydrocarbon nucleus CnH2n. It has already been pointed out (§ 143) that three different groups are thereby formed, which are named respectively after their simplest oxygen compounds. 374. 1. Aldehyde Derivatives.-In these the substitution has taken place on a single, terminal carbon atom of the nucleus. The simplest oxides are the aldehydes : CnH2n+1 do он он the first oxidation products of the primary monacid alcohols (§ 160). The names of their hydrocarbon radicals, CnH2n+1.CH, are derived from those of the radicals CnH2n+1 by addition of the terminal disyllable idene.' Thus from ethyl, CH3.CH2, there is formed ethyl-idene, CH3.CH. The general name alkyl-idenes is applied to the whole group. 375. 2. Ketone derivatives result when both substitution positions are on one and the same intermediate carbon atom. The oxides CnH2n+1 со CnH2n+1 are termed ketones, and are formed by oxidation of secondary alcohols (§ 160). 376. 3. Glycol derivatives are obtained by substitution of hydrogen atoms united to different carbon atoms. In the glycols or diacid alcohols they are replaced by OH. The first member of the series is a dicarbonide CH2.OH a diprimary alcohol. With greater carbon contents there occur in |