considerable quantity of alcohol. Both facts completely contradict the old view. The formation of ether by this process belongs to the most intricate but at the same time most instructive chemical processes; it is therefore worth considering at some length. 201. Preparation of Ethers from Alcohols and Sulphuric Acid.-On mixing an alcohol with sulphuric acid, an acid sulphate of the alcohol radical is formed with evolution of heat. The process is by no means complete, the greater portion of both ingredients remaining unchanged: aCnH2n+1.OH + bH2SO, = xCnH2n+1.HSO1 + H2O 4 +(a-x)CnH2n+1.OH + (b-x) H2SO. On applying heat, water and a part of the unaltered alcohol distil over, until the temperature reaches that at which ether is formed according to the second method (by the action of an alcohol on an acid sulphate), when ether occurs amongst the products distilling, and its formation continues as long as the liquid contains both alcohol and acid sulphate. In the last phase of the process, as soon as, by the continued external application of heat, the temperature rises above that necessary for the formation of ether, and when the free alcohol is nearly exhausted, large quantities of an olefine are formed, due to the decomposition of the acid sulphate: CnH2n+1HSO4 = CnH2n + H2SO4. As by these decompositions the sulphuric acid is regenerated and remains behind in the residue from the distillation, this latter can be used again and again for ether formation, the necessary fresh quantities of alcohol being added. Instead of adding alcohol from time to time, the process may be made continuous. For this purpose the alcohol and sulphuric acid are mixed together in such proportions, that the mixture begins to boil at the temperature necessary for the formation of ether; alcohol is then allowed to flow continuously into the apparatus, at such a rate that a thermometer immersed in the liquid shows a constant temperature under the continued boiling; there is then as much alcohol passing into the vessel as distils from it in the same time, in the forms of ether, water, or unaltered alcohol. Fig. 17 shows the apparatus used on the small scale. The flask, supported by a tripod stand over a gas flame, is provided with a triply bored cork; one opening contains the tube d leading to the condenser B; the second is for the thermometer t, which dips into the liquid ; through the third a funnel tube passes, reaching nearly to the bottom of the flask. As soon as the boiling alcohol-acid mixture has reached the desired temperature, the cock r of the alcohol reservoir E is opened to such an extent that the amount of alcohol flowing down the funnel tube into the liquid shall keep the temperature at the same point. The process might be interminable were it not that small quantities of the acid are changed in an unregenerable manner, there not only being a continual distillation of small quantities of organic com pounds of sulphuric acid, but also oxidation occurs at the expense of the sulphuric acid, so that small quantities of sulphurous anhydride are always evolved. The distillate collected in the receiver separates into two layers, the lower consisting mainly of water, the upper of ether. The latter is purified first by shaking with milk of lime, then repeatedly with fresh quantities of water, in order to remove any alcohol that may have passed over, and finally, after drying with calcic chloride, is submitted to fractional distillation. Many other not readily volatile acids, such as phosphoric, arsenic, boric, &c., act in a similar manner to sulphuric acid. 202. Small quantities of ether are also obtained by heating the haloid compounds of alcohol radicals together with alcohols to 200° in sealed tubes : xCnH2n+1Cl + yCnH2n+1.OH= (CnH2n+1)2O + HCl +(x-y)CnH2n+1Cl + (y-2)CnH2n+1.OH; therefore also, together with alcohols, when the haloid salts are heated with water to 200°-250°. After the reaction: xCnH2n+1Cl + yH2O=CnH2n+1.OH + HCl + (x-2)CnH2n+1 Cl follows further: +(y-z)H2O, (x-2)CnH2n+1C1 + zCnH2n+1.OH + ≈HCl + (y—z)HO =t(CnH2n+1)20 + (≈ + t)HCl + (x-z-t)CnH2n+1Cl +(-1)CnH2n+1.OH + (y-2)H2O, until a point of equilibrium is reached in the relative quantities of the ingredients and products. This point depends on the temperature, the quantities of the ingredients at starting, and the relative affinities coming into play. The formation of ethers by strongly heating alcohols with chlorides, bromides, iodides, and neutral sulphates of weak basic metals, such as zinc, tin, mercury, aluminium, iron, uranium, &c., was formerly of special interest. It is known that nearly all these bodies, when heated to high temperatures with water, are partly decomposed into free acids and basic salts, especially when the acid can volatilise; for instance, Al2Cl。 + 2H2O = ̃4HCl + Al2O¿C12. In every case these salts are more readily decomposed by alcohols, the negative constituent forming a compound with the alcohol radical. Zincic chloride heated with alcohol always yields some alcoholic chloride : xZnCl2 + yC2H2n+1·OH = ≈Zn<CH+CnH2n+1.Cl + (x −≈)ZnC!, +(-2)CnH2n+1.OH. Normal aluminic sulphate yields a basic salt and acid sulphate of the alcohol radical, according to the equation: Al2(SO4)3 +уCnH2n+1.OH=≈Al2(SO4)(OH), + 2≈CnH2n+1.HSO. +(x-2)Al2(SO4)3 + (y-2)CnH2n+1.OH. By the formation of haloid salts or sulphates of the alcohol radicals together with unchanged alcohol, all conditions necessary to the formation of ethers are given. The free acid thereby regenerated, probably assisted by the lowering of the temperature at the end of the reaction, converts the basic salt in great part back to the neutral compounds, so that it finally appears as though this latter had remained unaltered. These reactions had been considered to be catalytic processes previously to the correct explanation of their action having been discovered. 203. If two alcohols are allowed to react simultaneously on the etherifying agent (sulphuric acid, &c.), three ethers are obtained, two simple and one mixed; sulphates, &c., of the two different alcohol radicals being formed, of which each reacts on each of the two alcohols, converting them into ethers. These ethers are also obtained when a mixture of an alcohol and sulphuric acid is heated to the temperature of ether formation, and a second alcohol is allowed to flow in continuously. At the beginning only a single alcoholic sulphate is formed, which reacts with its unchanged L alcohol, (CnH2n+1.OH), to form the ether, (CnH2n+1)20, which is at first alone formed. If now the second alcohol, (CmH2m+1.OH), enters, it will form its acid sulphate with the still unaltered or regenerated sulphuric acid. This, reacting on the first alcohol, yields with it the ether, (CnH2n+1)(CmH2m+ 1 +1)0. At the same time the same ether is formed by the action of the already formed molecules of CnH2n+1.HSO4 on the second alcohol. In time the quantity formed of this second ether gradually increases, whilst that of the first ether soon diminishes. Soon, however, molecules of CmH2m+1.OH come in contact with those of CmH2m+1.HSO4, at first but seldom, later with increasing frequency. The second simple ether, (CmH2m+1)20, therefore, begins to distil over in rapidly increasing quantity, forming at length the sole product; this occurring as soon as the first alcohol has completely distilled over in the form of (CnH2n+1)20 and CnH2n+1.0.CmH2m+1° 204. Properties and Reactions.-The ethers are mostly liquids which distil unchanged, are either entirely insoluble or but little soluble in water. Their boiling points are invariably lower than those of the metameric alcohols. By reagents they are generally more difficultly attacked than the alcohols. By water at high temperatures they are partly converted into alcohols; e.g. a(C2H5)2O + bH2O=2×C2H5.OH + (a−x)(C2H5)2O + (b−x)H2O. By the halogen hydro-acids they are converted, on heating, into the haloid compounds of the alcohol radicals, most readily by hydriodic acid: CnH2n+1.0.CmH2m+1 + 2HI= CnH2n+1I + CmH2m+I+ H2O, and give salts with strong acids. Treated with chlorine, chlor-substitution products are readily obtained. By oxidation, especially in presence of water, they yield essentially the same products as the alcohols from which they are derived, the ethers of primary alcohol radicals therefore giving aldehydes and acids. 205. Methyl ether, or dimethylic oxide, C2H60 = CH3.O.CH3 (metameric with ethylic alcohol). Methylic ether is obtained by distillation of a mixture of wood spirit with four times its weight of sulphuric acid; the evolved vapours are passed through potassic hydrate solution, and the unabsorbed gas condensed in vessels cooled by a powerful freezing mixture. Methyl ether below -21° is a mobile colourless liquid, at ordinary temperatures an ethereal-smelling gas, of density 1-617. 37 volumes of it are absorbed by one volume of water. It burns with a strongly luminous flame. 206. Ethyl-methyl ether, or methylic ethylic oxide: C3H,O= CH3.O.C2H5, is prepared from sodic methylate and ethylic iodide, or better from methylic iodide and sodic ethylate, as a liquid boiling at + 11°. It is also formed, together with dimethylic oxide and ethyl ether, by heating a mixture of ethylic and methylic alcohols with sulphuric acid, ETHYL ETHER. 207. Ethyl ether, diethylic oxide, also known as ether only, C1H100 = C2H5.O.C,H,. In order to prepare this 9 parts of strong sulphuric acid and 5 parts of 90 % alcohol are distilled at 140°, under constant addition of more alcohol, until the amount of the latter has reached about five times the weight of the sulphuric acid employed. The ethereal layer of the distillate, after repeated agitation with water, is dried by means of fused calcic chloride and then distilled. In order to obtain ether completely free from the last traces of alcohol, which adhere with great obstinacy, it must be allowed to stand over bright pieces of sodium until all evolution of hydrogen ceases. Pure ether is a very mobile colourless liquid of penetrating odour, of sp. gr. 736 at 0°, boils at 35°, and has vapour density 2.565. It is very inflammable, its vapour mixed with air being ignited by contact with platinum black, and burns with a luminous flame; a mixture of its vapour and air is violently explosive. On account of its low boiling point, ether evaporates very quickly at ordinary temperatures, and causes thereby a great reduction of temperature. It mixes in every proportion with absolute alcohol, but not with water; 1 part of ether requires about 9 parts of water for solution, and itself dissolves about of its weight of water. On shaking a mixture of equal volumes of water and ether, and then allowing to stand quietly, it rapidly separates into two layers, the under consisting of a solution of ether in water, the upper of water dissolved in ether. Ethylic ether dissolves about of its weight of sulphur and of phosphorus; it is one of the best solvents for fats, oils, resins, and other organic bodies, and dissolves many metallic haloid salts, such as auric chloride, platinic chloride, ferric chloride, mercuric chloride, &c. A mixture of ethyl ether and dry bromine solidifies in a freezing mixture to a red crystalline compound, (C,H100),Br6, which is readily decomposed by water. By incomplete oxidation or imperfect combustion it is converted into aldehyde and acetic acid. With hydrochloric acid it yields some ethylic chloride. It is not attacked by potassium or sodium, but is very energetically by chlorine, which causes a violent explosion, with separation of carbon, when mixed with ether vapour. Chlor substitution products are obtained by passing chlorine in the dark through strongly cooled ether. The first formed are: Monochlorether, C,H,CIO or CH3.CHCI.O.C,H, (boiling point 97-98°); and bichlorether, C,H,CI2O=CH,CI.CHCI.O.C2H5, a liquid boiling with slight decomposition at about 145°, will be noticed at length further on. By further action of chlorine, which must be assisted by heating, bodies richer in chlorine are obtained, which on heating decompose with evolution of hydrochloric acid. Of these are known: Trichlorether, C,H,C,O= CHC12.CHCI.O.C2H5. Tetrachlorether, C,H,C1,0 CC13.CHCI.O.C2H5, a thick liquid smelling like fennel; and |