Page:Encyclopædia Britannica, Ninth Edition, v. 5.djvu/571

HYDROCARBONS.] CHEMISTRY 559 Many defines combine with sulphuric aoid, forming ethereal salts, which are converted by the action of water into sulphuric acid and the corresponding alcohol : C B H 2n + H 2 S0 4 = C n H 2n+1 HS0 4 . C n H 2n+1 HS0 4 + H(HO) = C B H 2B+1 .OH + H 2 SO 4 . General Methods of Formation, 1. By heating the C n H 2n+1 OH alcohols with dehydrating agents (H 2 S0 4 , C n H 2n+1 OH-OH 2 = C n H 2rt . 2. By electrolyzing C n H 2n (COOH) 2 acids : C n H 2n (COOH) 2 = C n H 2n + 2CO 2 + H 2 . 3. By heating N(C n H 2rt+1 ) 4 HO amines : N(C n H 2)!+1 ) 4 HO = N(C n H 2n+1 ) 3 + C n H 2n + OH 2 . 4. By the action of copper-coated zinc foil (Gladstone and Tribe s "copper-zinc couple") on the corresponding dibromides : C n H 2n Br 2 + Zn = ZnBr 2 + C n H 2n . Isomerism. The isomerides of the olefine series have been less completely investigated than those of the paraf fins. The formula of the first member Cethene) might be written CH 2 CH 2 CH 3 or or | OH 2 CH 2 =CH The first is probably the radicle in the free state, and the second the radicle in combination with Cl, Br, &c. The third formula represents a compound unknown in the free state, but known in combination. While the normal series are known as ethene compounds, the isomeric series are known as ethidene compounds. Similarly there may be 4 propenes, 9 tetrenes, &c. The following is a list of the C n H 2n hydrocarbons known at the present time. An idea of the general physical pro perties will be obtained from the table. ETHEXE SERIES OR OLEFINES. Names. Formulae. Boiling-points. Ethene or ethylene C 2 H 4 C 8 H 8 C 4 H 8 C 5 H 10 t eH 12 5" tgHie CH 18 CioH 20 C 15 H 30 ^igHaa C 20 H 40 C S7 H 54 - BO^GO Gaseous -18 C. 3 35 65 95 120 140 160 248 275 390 -400 ? melts at 57 375 (?) 62 Propene or propylene Tetrene or tetrylene Pentene or amylene Hexene or hexylene Heptene or heptylene Octene or octylene Nonene or nonylene Decene or paramylene Pentadecene or triamylene Hexdecene or cetene Yigintene or tetramylene Heptivigintene or cerotene Trigintene or melene . The numerous isomerides of the higher members of the series cannot be described within the limits of the present article. The first member, ethene, is a colourless inodorous gas, which can be condensed by cold and pressure. It burns with a brilliant flame, and is the constituent to which coal- gas chiefly owes its luminosity. Several defines can be synthesized from other hydrocarbons; propene, for in stance, by passing methane and carbon monoxide through a red-hot tube : Third Series, C n Ho,,_ 2 - General Properties. These hydrocarbons are capable of acting as tetrad radicles uniting with 4 atoms of 01, Br, fcc., and producing tetra-haloid paraffin derivatives ; or the combination may be limited to 2 atoms, thus forming di-haloid defines. Similarly they can combine directly with one or two molecules of haloid acids, producing C n H. 2n _ l Ha , or C n H 2n //a 2 . These combinations show their relations to the defines and paraffins. Their relation ship to the latter parent hydrocarbons is further shown by the ultimate action of chlorine : C n H 2n _ 2 01 2 + Cl2 = C u H 2n _ 2 Cl 4 . Perchlorinated paraffin. General Methods of Formation. 1. By the action of an alcoholic solution of potassium hydroxide on mono-haloid olefine derivatives : C n H 2rv _ 1 //a + KHO = C n H 2n _ 2 + KHa + OH 2 . 2. By the electrolysis of C n H 2B _ 2 (COOH) 2 acids , C n H 27 _ 2 (COOH) 2 = C n H 2n _ 2 + 2C0 2 + H 2 . The following is a list of the hydrocarbons of this series : ETHINE OR ACETYLENE SERIES. Names. Formula. Boiling-point. Ethine or acetylene r 2 H 2 L 3 n 4 C 4 H 6 C 5 H 8 C^HK) C 7 H 12 ^gttu C 10 H 18 Vls^iS CieHao Gaseous 18 C. 45 80 107 133 165 225 280 Pro pine or allylene Tetrine or crotonylene Pentine or valerv lene Hexine or hexoylene Heptine or cenanthylidene. . . Octine or caprylidene Decine or decenylene Pentadecine or benylene Hexdecine or cetenylene But few of the isomerides of this series are known. Diallyl, C 6 H 10 (b. p. 5i C.), is isomeric with hexine, and rufylene, C 10 H 18 (b. p. li/0), with decine. Ethine or acetylene may be formed directly from its elements by causing the electric arc to pass between poles of dense carbon in an atmosphere of hydrogen. It is formed also by passing a mixture of methane and carbon monoxide through a red hot tube (CH 4 + CO = C.,H 2 + OH 2 ), bypassing chloroform vapour over red hot copper (2CHC13 + 6Cu = 3Cu 9 Cl 2 + C 2 H 2 ), and by the imperfect combustion of most organic compounds. Etliine is a colourless, incon densable gas, having a characteristic odour. It is absorbed by an ammoniacal solution of cuprous chloride, forming a red precipitate of cuprous acetylide, (C^Cu^O, which when heated with HC1 furnishes pure ethine, so that this is a convenient method for purifying the hydrocarbon. Ethine can be made to combine with nascent hydrogen with the formation of ethene : C 2 H 2 + H 2 = C 2 H 4 . Fourth Series, C n B., 2n _ i . The hydrocarbons of this series may be conveniently divided into two groups. The first, consisting only of one member, pentoiie or valylene (C 5 Hg), is related to the pre ceding series of hydrocarbons, since, by the addition of bromine the hexabrom-paraffin C 5 H 6 Br 6 is formed. The other group is composed of decone (Cj H M ) and a series of hydrocarbons known as terpenes, having the gene ral formula C 10 H 16 , and found in the essential oils of various plants, chiefly of the orders Coniferce and Aurantiac&s. Terpenes. These hydrocarbons are found in the wood, leaves, &c., of Coniferous trees, and in the essential oils of lemon, lavender, bergamot, juniper, &c., &c. Many of these oils contain oxidized bodies besides terpenes. The terpenes possess very similar chemical properties, differing chiefly in their boiling-points (which range from 160 to 176C.),

specific gravities, and action upon a ray of polarized light,