Document 2jqG0VgpY2G2e32K6XzKjea4N

ucc 002694 - - 4 a' ' ' m. Nieuwland, Julius A., and Vogt, iTichard R,[ Chemistry of Acetylene j Reinhold, 1945 (A.C.S. Monograph No, 99) TillS CHEMISTRY OP ACETYLENE ; (30) I. G. Farbcnind. A.-G., Brit. P. 280,885 (1927); C. A., 22,3499 (1028); French P. 013,387 (1027); C. A., 2S, 1410 (1020). (31) I. G. Farbcnind. A.-G., Brit. P. 377,103 (1031); Bril. Chtm. Ah*., 1032B, 020; French P. 724,470 (1031); C. A., 20,4623 (1032). Schilling and Stadlcr (to I. G. Fnrbunind. A.-G.), U. fl. P. 2,020,120 (1030); C, A., 30, 1010 0030). (32) Hull and Imperial pliomicoj .Industrial, ltd., Brit. P. 331,010 (1020); C, A., 20, 110 (1031). (33) lloraley and Holley, to Imperial Chemical Industries, Ltd., Brit. P. 331,054 (1020); C. A., 25,110 (1031); U. S. P. 1,054,141 (1032); C. A., 20, 3304 (1032). (34) Cro)l and Burgin, Brit. 1>. 400AM (1033); C. A., 28,2100 (1034); U. 8. P. 1,005,100 (1034); C. A., 20, 8474 (1034). N.V.da Bataateche Petroleum Mnatacliappij, GormanP.000,343(1034);e.A.,20,1014(1035);French P.751,284 (1033); C. A., 20, 1053 (1031). (35) Keller, Kkim. Tvtrdopo Topline, 8, 1140-55 (1037); C. A., 32, 4010 (1038). (30) Lliam, U. S. P. 2,003,080 (1037); C. A., 31,710 (1037). (37) Taylor, U. S. P. 1,000,088 (1035); C. A., 20, 3363 (1035). .. (38) Mali get (to Air Reduction Co.),U.S.P. 1,000,065 <Wa3);C.A.,27,29fia. (1033); > Brit. P. 401,531 (1033); C. A., 33, 2371 (1034); French P. 740,025 (1033); C. A., 28, 402 (1034). - (30) MUltcr-Conradi,Eieenhut and Schilling (to I. G. Farbcnind. A.-G.), U, S. P. 1,038,083 (1033); C. A., 28,1010 (1014). (40) Johnson (from I. G. Furkcuind. A.-G.), Brit. P. 326,817 (1028); Brit. Chem. Ah., 1030B, 440. ., (11)hlinUlcr of Navy (Hujio, inventor), Jap. P. 100,413 (1035); C. A., 28,4218 (1035). (42) Broun, Z. anger#. Chem., 43,700-8 (1020). (43) Wulil, U. S. P., 1,030,001 (1034); C. A., 28,1304 (1034). (44) Gcsellscliaft fUr Liudc'a EWmuacl.incn A.-G., Brit. P. 408,014 (1037); C. A., 32, 0 (1033); French P. 815,204 (1937); C. A., 32, 057 (1038). p(4S) Pyxci(u>Shell Development Co.),U.S.P. 1,1185,518 (1035); C. A.,20,1235 (1035). (40) I. G. Farbcnind. A.-G., French P. 057,001 (1020); C. A., 24,1110 (1030); Brit. P. 303,732 (1030); Brit. Chut. Alt., 18320, 401; Gorman P. 501,101 (1031); C. A., 30, 3315 (1034). ' (47) Askanaay (to Soe. anon, pour 1'iudustrio claim, a Bilo), German P. 650,770 (1020); C. A., 27, 313 (1033); French P. 078,630 (1020); C. A., 24, 3510 (1030); U. S. P. 1,805,422 (1032); O. A., 28, 4347 (1032). (48) I. G. Farbcniud. A.-G., Brit. P. 325,300 (1030); Brit. Client. Aln., 10303. 400; French P. 068,160 (1030); C. A., 25, 762 (1031); Gorman P. 550,770 (1032); Frill., 17,127-0,^ . (40) Deutsche'Gold- und Silbor-Schcldoanslalt vonn. Tloossler, Gorman P. 043,210 ' : (1037); C. A., 31,4170 (1037). -- (60) I. G. Farbeiiind. A.-G., Brit. P. 276,324 (1020); C. A., 22,2673 (1028); French P. 011,400 (1028); CAcM.Zcalr.,1026, II, 1036; French P.067,027 (1028); C, A., 23, 4231 (1020). '' ; (51) Forgusun nml Imperial Chemieul Industries, Ltd., Brit. P. 342,771 (1020); C.A., 26, 643U (1031). (62) Hirst und liniierial Chemical Industries, Lid., Brit. V. 302,516 (1028); C. A., ;. . 23, 4231 (1020). i , <i 10. The laboratory purification and analysis of acetylene. For labora tory uao acetylene usually ia either generated from calcium carbide or drawn from a commercial storage cylinder. If carbide is employed it is preferable to use a curbido to water typo generator, observing precautions ' against localised overhauling. It is also udvisablo to use u precipitant or an oxidutivo purifying agent to remove traces of phosphino and other I .;.m: , v- : 1 .. . ' , , , ; PHYSICAL PROPERTIES, PREPA RA T10N, PURIFICA TION 37 impurities. (See Cliapter 1, Section 4.) However, it is usually more convenient to uso the gas from a storage cylinder. In this case most of the impurities arising from carbide have been reduced to n proportion which is negligible if the gas is to be used ns a raw material for laboratory syntheses. Hie gas from a cylinder docs contain acetone in Quantities which increase with decreasing pressure in the cylinder. Sodium bisulfite solution has been employed to remove acetone. Passing the gas through strong snifui ic acid in qn efficient wash bottle also removes acetone and part of the otlier truce impurities but may introduce sulfur dioxide and acid spray. These may be eliminated by a soda-lime tower or by n dilute sodium hydroxide wash followed by a drying agent. If it is essentia! to remove oxygen from .the gas an alkaline solution of sodium hydrosulfitc containing a little antlwaquinone sulfonic acid (J) may bo placed in the train, lloriuti (i?) and Conn, Kistiakowsky and Smith (3) have described somewhat more elaborate purification methods. However, acetylene may contain traces . of impurities such as hydrogen, nitrogen, methane, or ethane which can not be removed by chemical reagents. Accordingly if the gas musTTuT " exhaustively purified it appears essential to liquily and distil it. This procedure requires spccial( technique and precautions which tlo not seem to have been adequately described in the literature. For tho qualitative detection of acetylene n variation of the cuprous acctylidc precipitation is always used, since the characteristic red color of tho acctylidc can bo seen even when present in minute quantities. (See Chapter II, Section 5.) However, the acctylidc is readily oxidized with darkening by air in an alkaline medium, and a reducing agent sucli as hydroxylamino is necessary to preserve tho pure red color. Test papers ` based on this reaction have been described (if). For a much more sensitive test, modifications of Flosvay's solution have been recommended (5). Tills consists of nunmmonincnl cuprous chloride solution containing gelatin which acta us a protective colloid to keep the aeelylidc in a fine stale of division so that' its color is inoro readily observable at greul dilution. Czaco (5) states that this reagent is sensitive to acetylene in concentrations of 2-4 pur cent if proper precautions arc laken. llosvuy's solution, also 1ms been used fur the colorimetric estimation of Acctylcno (S,C). However, tho color depends upon both the size of the colloi dal particles and the absence of Impurities such ns traces of hydrogen sulfide or larger quantities of oxygen or carbon dioxide. Accordingly, most irives~ tigntors have preferred to estimate the quantity of ucclylule formed either by careful drying and weighing as the explosive carbide CjCu- (7) or better, by dissolving tbo acctylido in acid and determining the copper by any standard method (3)- Sineo tho red cuprous aeclylido in au ummouincnl solution is readily attacked by oxygenwhich darkens tho color and may alter the 38 -THE CHEMISTRY OP ACETYLENE ratio of copper to carbon, it ia recommended that a reducing agent such aa hydroxylainine or hydrazine bo added to tho ummonincnl cuproua cldorido eolution (5).. Chcvastelon (8) and Ross and Trumbull (10) have described tho estima tion of acetylene, especially in tho presence of ctliylcuc, by titration of tho nitric acid liberated by tho gas from a neutral silver nitrate solution according to tho equation, Ctll* + SAgNOj -- CjAgjAgNOi + 2IINOj. Iloeppncr and Wills(fitter and Marchmann (11) report that tho method is . not very reliable. Novotny (12) proposed that the silver in the precipitate bo determined. Lcbcau and Damiens and Wellers (f2) used a slightly alkaiino solution of mercuric iodide and potassium iodide to precipitate i acetylene in the presence of olefins. =. In gas volumetrio analysis methods,reagents, containing copper,silver or mercury which are capable of absorbing acetylene are nearly always capable of taking up lesser quantities of olefins, diolcfins, carbon monoxide or higher acetylenic hydrocarbons,' so that methods depending upon loss of gas volume in such reagents axe of questionable accuracy. A microchemical method far the estimation of acctylcno by reaction with & bead of cuprous chloride made alkaiino with ammonium hydroxide has been proposed (/,(). Tho analysis of carbide acetylene for common impurities bus been described in several treatises on calcium carbide and acetylene (see ltcf. 1. Introduction) and a few reviews (IS). A number of methods which describe special adaptation of these procedures to particular gas mixtures cannot be discussed in this work. References (1) Feiser, J. Atn. Chm. Sot., 10, 2030-17 (1921). (2) lioriuli, .Sri. Paper] Jnti. Ptyi, CAiut. iieitarcb (Tokyo), 17,130 (1931); C. A,, 20,2101 (1032). (3) Conn, Kieliakoweky and Smith, J. 4w. Clem. Soo,, 01,1808-70 (1039). (1) Liorena, Aiuil. Fie. Quint., 10, 130 (1012); 11, 320 (1013). Denigoa, Rail, we, pJiam,iloriieatts, 1021, No.2; jfrperf.pAanN.,83,232(193l);C..4.,IS,305(1022). (6) Ilwvay, Btr., 32, 2007-0 (1899); Z, ami. Chm., 10, 123-4 (1901). Chaco, Z. aitgeiv. Chun., 11, 388 (1001). Ilicee, lin'd., 11, 701-3 (1931). Sclmlio, ibid., 11, 703 (1031). Pioleck and lCotbowuki, ibid., 11, 309-12, 388,701 (1031). No votny, Coll. Cttchelav. Cheat. Cawwumcaiitmi, 0, fill-27 (toll); C. A., 20, 2878(1036). (0) Weaver, J, Am, Ctm, Site,, 36, 3S2 (1010). Selmlxo, Z. angew. Chun,, 29, 311 (UU0). (7) Schtihor, Z. anul. Ciwt., 18, 37 (1000). ' (8) Btheiher, Her., 11, 3810 (1908); Muller, RuM. toe. cbim., 27, 09 (1920); Arnold, Mdlluuy and liimnicrmana, Btr,, 3,1031 (1920); WillsUllcr end Musciimann, ibid., 13, 939 (1020). (9) Cboyaatolon, Cempl. rend., 121, 21fi (1807); Tucker and Moody, J, Am. Cheat. See., 28. 071-4 (1061). , one) Trumlml) ' J- ** PHYSICAL PROPERTIES, PREPARATION, PURIPICATION 30 (11) IKtujijiuur, Z. Nahr. Qenu'nat., 31,163 (1917); WillutKUor aiul Mtuwhitumn, Her., 63,1K1U (1920). (12) Novotny, CVHeclion Crecfieitov, Chm. Comtininicatione, 7, 81-0 (1036). (13) LoIkmhi and Daraianti,.Wipt. rend., ICO, 07 (1013); Wellora, Sluli r (14) Blacoi, MacDonald and Leighton,' Ind. Eng. Chun1.1A40n(a1l9,2E21d-., 6, 272-4 (1933). (16) Ilerites, Chm. Lilly, 21. 493-0 (1930); C. A., 26, 2904 (1931). Konwhulc, Actlylen Win. Ind., 3, 118-22 (1932); C. A., 20, 3029 (1034). Awman, Hid., 36, 184-0 (1032); C. A., 28, 3020 (1034). Stmlievekii and Choekhovick, Ztnodtlnva Lob., 6, 220-2 (1039); C. A., 33, 9198 (1939). - ' ' i'1;' i i i r' *: ' i 'ii, 1 - |1 ;* * I >> " | V i * ' , t 10 THE CHEMISTRY OF ACETYLENE References (1) Hare, L'lmtitut, 1810, 312; Am. /. Set. (1), 3T, 209 (1839). (2) DcviUe and Debrayc, Ann. mince (S), It. 1 (1859); Jahresber. dber die Fort- eckritte der CAemi'e, 1869, 251-0. (3) Welder, Ann., 121, 220 (1802). (I) Willson, 0. S. V. 192,377 (1893); Progress Ago, 1898,61; Am. Manufacture*, 1698, Dec., 10; Brit. F. 10,312 (1801), 16,703 (ISM); J. Sac. Chet*. Ind., 16,103 (1890); Bril. P. 16,300 (1896); ibid., 10, 682 (1800). Willson and Suclcort, J. Fra,Min. I,ut., 139, 221 (1893). (6) lioclira, U. B. P. 662,020 (1896); Mineral Induitrg, 6, Of (1901); Teehnabgiel, 0, 9, 203 (1901). (0) Moissan, Campt. rend., 116,1031-3 (1892); ibid., 118,601-6 (1891); Buli.eec.c3m. (3), 11, 1002-7 (1894). (7) Uullier, German F. 77,108 (1894); Ckem. Zentr., 1896,1,191. ' . (8) Eimer, Trane. Am. Elcetrockem. Roe., 61, 73-8 (1927). (9) Hilbert and Frank, German P., 92,838 (1805); CArm. Zenlr., 1891, U, 878. Morelicad, U. 8. P. 802,092 (1907); C. A., 1, 3909 (1807). Yasuda, Jap. P. 35,600 (1619); C. A., 14,3023 (1920). Sue. d'dtudes chiioiques pour I'Industrie, French P. 075,411 (1929); C. A., 24,2842. SwissP. 134,012 (1928); C.A.,24,1709 (1928). Seyfried, U. 8. P. 1,777,582 (1930); Bril. Clem. Abe., 1931B, 637. (10)Jacobsen, German 89,959 (1896); Clem. Zenlr., 1997,1, 628. Iamb, German F. 117,920 (1899); Ckem.. Zentr., 1901. I. 427. Voirat, French P. 712,003 (1931); C. A., 28, 2021 (1931). (II) Harrison, Brit. P. 477,100 (1637); C. A., 32, 4290 (1638). (12) Krylov, Meiallmg, 12, Ho. 7,16-24 (1927); C. A., 83,0167 (1938). (13) Anil, Cttmpl. rend., 204,1340-1 (1937). (14) Allinand and Williams, J. Sac. Chen. Ind., 38,303-4R (1919). Anon., Bnpiacer- ing, 87,405,443,477,622,510, 729 (1909). Anon., J. fawr tleclr., 38,105-7 (1927). Bergeron, Bull. soc. Prune, elec., 8, 76-80 (1925); Be*, gen. elec. 22, 797-802 (1027). MantelI, "Industrial Electrochemistry,'' pp. 406-24 (1031). Mcno(iiiui, AM iet. Veneto tci., 64, 687-60 (1936). (15) Plugin, Eng, Mining J., 197,479 (1918). Brunet, Be*, pen. elec., 6,913-23 (1920). Purasuki, J. Ckem. Ind. Japan, 26, 24-30 (1922). Baumann, Ckem. Ztg., 60, 029-31 (1920). Sctdunibergor, ibid., 60, 978 (1929); Z. impel*. Chon., 40, 14V-6 (1927). Go), Ckem. Ztg., 61,251-2 (1927). Danuoel, Z. Blellredtem., 36,474-82 (1930). (10) AkliuugcsulUchaH (Or StickstoIFdUnger, French P. 809,308 (1937); C. A., 31, asm (1637). (17) HuB nod Facrster, Z. anorg. a!1pm. Clem., 131, 321-47 (1923). UulT, Z. E(cktracktm., 30, 350-94 (1924). Hull nut) Juaupliy, Z. Quurg. atlffcm. Ckem., 163, 17-32 (1920). Belliundtorger, Ckem. Ztg., 60, 070 (1929); Z. aupeie. Cheat., 39, 213-20 (1629); ibid., 40, 141-0 (1927). Denned, Z, EicUrockem., 30, 474-82 (1930). Dutoit and lliMsiur, J. drim. phys., 29, 23H-41 (1932). {18) Morchcad, U. S. P. 825,234 (1007); C. A.,1,116 (1907). Schltiidur, Z. Makiro- cktia., 26, 409-14 (1019). Sue. aitou. I'exploitation brovot* Jullion, French P. 009,459 (1020); Fr. P.098,576 (1929); C. A., 11.1680 (1030);C. A.,26,3258 (1931). Hilger, German P. 622,573 (1925); C. A., 26, 3678 (1031); Cur. 541,395 (1020); C.A.,20,1890 (1032);Cor. 580,202 (1033); C.A.,27, 1714;Cur. P. 600,170 (1034); C. A., 28,4321 (1934). llibi, Jap. P. 00,215 (1031); C. A., 26,2028 (1931). Car- tous.CAofeur el ind., IS. 410-21 (1038); C. A., 32,0951 (1938). (10) Domenico, Sail. cent. Yolpi ciletrologia. No. 2, 11-12 (1038). (20) Gardener, Brit. P. 490,204 (1938); 490,205 (1938); C. A., 33, 3641-2 (1939). (21) Pincas, Chew. Ape, 87, 109-70; C. A., 31, 8830 (1837). PHYSICAL PROPERTIES, PREPARATION, PURIFICATION 11 4. The generation and purification of acetylene from carbides.* The acetylenic carbides described in the preceding sections were found by the earliest investigators to react rapidly with water, giving acetylene and the corresponding metallic hydroxides. Tho heat of hydrolysis (i) may produce localized temperatures high enough to polymerize a part of tho acetylene, unless overheating is prevented by the use of excess water or by some other means. The hydrolysis of calcium carbide has of course been' studied most thoroughly, and the heat of this reaction has been reported by Lewes (S) to be about 475 cal. per gram of pure carbide, and by Mason, Anderson, and Jane (5) as 10ft Btu per cubic foot of acetylene generated. Lewes (8) claimed that when a minimum of water reacts with a moss of carbide a part of the acetylene may react with steam to give carbon mon oxide and hydrogen; and in a few cases localized decomposition of acetylene to hydrogen und carbon has been reported. Besides moisture, air, finely divided bolids, and condensation products resulting from overheating, the crude acetylene also may be contaminated with a small percentage of other gases arising from impurities in commercial carbide* (3). Nitrogen, sulfur, phosphorus, silicon and arsenic may be present in carbide in combination with calcium or other metals. On treatment with water the hydrides, ammonia, phosphine, silicomethane and amine, may bo evolved to some extent, while most of the hydrogen sulfide is held in the alkaline solution. Modern methods of carbide manu facture minimize these impurities by careful control of the composition of the diargiiig materials. Analysis of acetylene generated from a typical modern carbide is said to show the presence of .015-.025 per cent of phos phine. less than .015 per cent of ammonia, less than .01 per cent of hydrogen sulfide, and less than .00011 per cent of~arsinc. At the high temperatures occurring when little water is present during the hydrolysis of calcium carbide, the simple hydrides above noted if present limy lie eoiulcnscdlvitlT acetylene to give volatile orguiticTlcrivulivcs~whli-li arc diliicuit to remove. Kennedy and Helm (Hi) havo identified divinyl sulfide as an important impurity, mid state that mom is present if the Icmpcralurc of hydrolysis of tho carbide is high. filicy have suggested removal of tins impurity by scrubbing with Chloramine T or sulfuric acid. Hydrogen is sometimes present in very small quantities. Methods for tho estimation of im1 purities in crude acetylene Iiavq been reviewed by Brown (/,) and others,t A high reaction temperature during tho hydrolysis of carbides results in a decomposition and condensation of tho acctylcna which both con- * The generation of acctylcna from carbide, and the impurities and purification of tlicgas havo been extensively discussed in special treatises; see Introduction (1,3). t Soe Introduction (1, 8). ucc 002697 12 the chemistry of acetylene tumiliaria the product and reduces tho yield. Ac,..irdingly, it lias keen lire commonest practice to prepare occtylcnu by the total immersion of calcium carbide in a comparatively largo volume of water which acts us a cooling medium. Methods and devices for tiro hydrolysis of calcium carbide by this method have been studied extensively, but most of the technical litoraturo* covers small automatic generators for local or domestic acetylene supply. Recently Mason, Anderson and Jane () have described a large-scale method of hydrolysing calcium carbide using little more than an equivalent quantity of water, which is based to some extent on earlier methods (5). This procedure consists in spraying the crushed carbide either in a ball mill or in a rotating screen drum with a minimum of water, and con tinuously separating the powdered calcium hydrate. By this method localised overheating is prevented and no temperature above 240F was observed. A few other recent patents and articles (7) describe the hydroly sis of calcium carbide with a minimum of water. The Prcstolite Company controls United States patents (7a) on a process and apparatus by which water is brought into reaction with calcium carbide near the bottom of a cylindrical reaction chamber, provided with an agitator rotated about a vertical axis. The acetylene and powdered calcium hydroxide rise to the top of the cylinder, and in one modification the powdered hydroxide, which overflows the top of the cylinder fills an annular seal similar to a liquid seal. If the recovered dry hydrate could be converted to a briquet or lump form (&), it could be used profitably, for calcium carbido manufacture. Since in some localities the accessible supply of limestone suitable for carbide manufacture is somewhat limited, recovery of the calcium hydroxide is of interest. Even'when prepared in the best typo of generator from a good grade of carbide, commercial acetylene usually contains traces of impurities. These are said not to be deleterious in the gas used for welding or cutring (11, IS) but may act as poisons for tils' catalysts employed in tho chemical utiliza tion of acetylene. .For some purposes it has been common practice to oxidize these impurities, particularly phosphine, by reagents which scarcely attack acetylene and to remove Clio acidic oxidized products by contact with alkalies or by precipitation. Solutions or porous masses containing calcium hypochlorite or potassium permanganate were at one time used or proposed, and masses containing chromic acid appear to have been exten sively used in Europe. A purifying material, which was originally patented by Granjon (16) and which is at present used in the U. S., consists of a mixture of ferric chloride, ferric oxide, manganese dioxide, mercuric chloride, and cupric sulfate. The mercuric chloride appears to bind the * Sea Introduction (1, 2). PIIYSICAL PROPERTIES, PREPARA TION, PURIPICA TION 13 phosphine in a complex which is then oxidized by the ferric salts, and tho cupric sulfate catalyzes the rcoxidution of the ferrous suits by air and thus regenerates the purifying materiur This method is said to remove 05 per cent of the phosphine. At the present time nitre cake is said to be used also in the commercial purification of acetylene. Oxidation of phos phine by sulfuric acid of about 85 pur cent concentration at about 70 is reported to bo an industrial method of purification. Methods of evalu ating commercial preparations for the purification of acetylene and some comparative tests on such materials have been published (9, 13, 14). An older proposed method of purification consisted in tim complete precip itation of these impurities by cuprous chloride or mercuric chloride with other chloride salts. However, these solutions are not perfectly inert toward acetylene, and a small percentage of volatile addition products usually was formed. The drying of acetylene by refrigeration, or by the use of aluminum oxide with proper precautions, or by countercurrent washing with saturated calcium chloride solution are said to be accepted industrial practices. ' There is reason to believe that a traco of oxygen is a very important impurity in acetylene to be used in certain syntheses, but this possibility has received little attention. A small quantity of oxygen is known to bo very deleterious in tiro preparation of vinylacetylcne, and probably bus effects in tire polymerization, halogcnation and hydration of acetylene. The acetylene mixtures prepared by pyrolitic processes are probably more nearly free from oxygon than acetylene derived from carbide. Both commercially and in tiro laboratory, oxygon can best be removed from acetylene by washing with an aqueous alkaline solution of sodium hydro- sulfito containing a small percentage of antliraquinonc 0-sulfouic acid (10). Gaseous hydrocarbons, carbon monoxide and hydrogen arc much more difficult to remove from acetylene; the total elimination of these impurities is not attempted commercially, sinco thoy arc not particularly deterimcntal in tho use of acetylene either as a fuel or for chemical synthesis. References (1) Fal'kovicli, Khimitroi, <, 442-6 (1034). (2) I.owes, J. Soc. Chtm. Ind., 17, 532-42 (1808). (3) Willgerodt, liar., 18, 2107-8 (1805). T.uiiks end Ccdurcrcuti, Z. angew. Chtm., 10,061-5 (1807). Meissen, Compt. rtnd., U7,457-4)3 (1808); Ann. chin,, phye. (7), 18. 313-61 (1809). Wolff, Z. an9cup. Chtm., 11, 031-41 (1808). Criro, J. Qutlelcuchtmg, , 010-7 (1890); Chtm. Zcnl., (1809) II, 642. Kcppolcr, J. Oat- beltuehlvnff, 45, 777-82, 802-5, 820-25 (1002); Cl,cm. Zenlr., 1902, II, 1481-5. Dullior end Maquonno, Ret. gen. tie chimie pure el uppl., 8, 348-50 (1003); Cheat. Zentr., 1903. II, 043. (4) Brown, Caracgie-IUinois Stool Company, Pamphlet (1027); C. A., 21, 3327 (1027). ' (5) Mason, Anderson and Jana, Can. Chtm. Mel., 10,183-4), 102 (1036). ucc 002698 14 THE CHEMISTRY OF ACETYLENE (6) Dolan, U. S. P. 638,443 (1300). Dickinson, U. S. P. 004,130 (ISOS); U. S. P. 671,001 (1901). Davies, U. S. I*. 701,852 (1902). Gibbs, "Lighting by Acetylene," p. SO, (1809). (7) WcibciaUn nrul Walter, U. S. P. 1,017,120 (1934); C, A., 28,2371 (1031). U. S. P. reissue 20,527 (1937); C. A., 31,8519 (1937). Mues (to I. G. Fnrbcmud. A.-G.), U. S. P. 2,122,889 (1938); C. A., 32, 6812 (1038). I. G. Parbehind A. C., Ger. P. 048,687 (1937); C. A31,8510 (1039). Mues, Z. Kompr.ftnu. Quit, 33,57-00 (1937); C. A., 33,0093 (1939). Dayerische SliekstoiT-Werke A. G. (Wilm, Volkniann end Kscss, inventors) Cor. P.67,103 (1939); C.A.,33,6319 (1939). Autofienwert Sirius Gjn.b.ll. (ilecker, inventor) Gor. P. 673,779 (1939); C. A., 33, 6099 (1939). (7s) Kojolo and O'Brian, Brit. P. 463,601 (1938); C. A., 32, 7219 (1938); U. S. P. 2,201,181 (1910); C. A., 31, 6016 (1910). O'Brian, U. 6. P. 2,189,762 (1910); C. A,, 34, 3956 (1940). Ness and Kojolo (to PrestoUts Co.) U. 3. P. 2,233,108 (1911), 2,233,100 (1911); C. A., 36, 4912 (1911). (8) Winter end Hartmann, U. S. P. 2,017,558 (1936); C. A., 29,7834 (1935). (0) Sumiyasad Yamads, J. Cheat.See. Japan,33,537-9 (1930); C. A.,26,1360 (1931). (10) Ficsor, J. Am. C'ktrn. See., 40, 2639-47 (1924). (11) Rimarski, Kantor and Streb, Fereeh. Gebiete Ingenieuru., No. 317 (1929). (12) UolihaUscr, Aulogcne Uelallbearb., 23, 286-96 (1931); 24,192 (1931); C. A., 25, 3302 (1931). (13) News Bulletin ot the Compressed Gas Muuif. Aaaoo., July 21 (1631), New York. (14) Sberun, Cbem. Fabrik (1938), 207-10. (15) Granjon, Fr. P. 431,137; U. S. P. 1,011,601 (1013); J. VAeetylbne, (1034),457-61. (16) Kennedy sad llolm. Can. Cheat. Process Jiul*., 23,499-5 (1939). 6. The equilibrium of acetylene with carbon and hydrogen and its bearing on Hie direct synthesis, decomposition and storage of acetylene. Bertiiclot (J) prepared small quantities of acetylene by means of an arc between carbon electrodes in on atmosplicro of hydrogen. Dowar (2) concluded that this reaction resulted solely from the high temperature attained. The equilibrium of carbon and hydrogen with acetylene has been investigated by a number of workers (3-7,9-11). In tire equilibrium mixtures produced, cititer from acetylene or from the elements, little ucelylenc appears to exist between 1000 and 1700, and above 1700" the con centration increases with rising temperature up to a point at which llte equilibrium changes Ijccuuso of the formation of atomic hydrogen. Frost (it) slatus that considerable yields can be obtained only in tho region of 3)00* to 3200". Tito continuous formation of acetylene in tills high lemiiemturo range may tie due in part tit a tendency of complex enrhon structures to break down under these conditions into Ct groups rather (Jam into any oilier simple units. Tim proportion of ueetyleno recoverable from Lite carbon am in liydrogen lias been reported as alumt seven Lu eight per cent. Since a higher concentration of acetylene can lie made by the pyrolysis of hydrocarbons, the synthesis of acetylene from the elements has not usually been considered suitable for commercial application, al though Heading (IS) hits patented an arc apparatus for this purpose. A somewhat related method consists in cracking hydrocarbons iu the oloctric arc in the presence at finely divided carbon (22). INIYSICALPROPERTIES, PREPARATION, PURIFICATION 15 Of greater practical significance is the fact that acetylene, being an endothermic compound, can decompose to its elements with the evolution of heat. The decomposition at pressures not much above one atmosphere will first be considered. Berthciot (14) noted that at atmospheric pressure and a dull red heat in vessels of inert' material, polymericliun was the principal reaction of acetylene (see Chapter V, Section 2), while at some what higher temperatures the polymerisation was associated withdecom position to carbon and hydrogen. He considered that this decomposition took place through a mechanism involving the formation and total de hydrogenation of. polymers. Ilabcr (16) observed that heat was evolved during these reactions. It was later found that tho decomposition of acetylene was practically complete in the range 1150-1325 (7, 16), and that noticeable decomposition began in porcelain tubes at about 480 and became the chief reaction at 800 (9). Several metals have been found to increase the rates of polymerization or decomposition and to influence somewhat the nature of the products. Somo of these metals, when finely divided, have also been reported to initiate tho reactions at comparatively low temperatures. Tims Moissan and Mourcau (17) found that pyrophoric iron, nickel and cobalt, and finely divided platinum became incandescent when placed in a rapid stream of acetylene at room temperature, and noted the formation of hydrogen, carbon and oily products. Since these reactions are promoted by increased heat and pressure, it appears probablo that the catalytic cfTcct of metals is at least partly duo to the localized heat of adsorption of the acetylene and also to the high concentration of acetylene in the adsorbed layer. Bcrthelot (5) first discovered tho catalytic decomposition of acetylene by iron. A similar effect of iron, nickd and cobalt has been observed by several workers at temperatures botween 200 and 400 (1S-S). Extensive decomposition of acotyieno in contact with iron has been noted at higher temperatures (t4~tS), and a few iron coinpcnuids Imvo been found to produco a similar effect (tS, SO). Finely divided platinum (IS, 31) unit palladium (St) Imvo been reported to induco tlm dccom)>asitioii of acetylene nl moderate temperatures. Copper and to a lesser extent a few other metals can.so tho condensation of nenlytcuo to cupvcno at about 25(1 (sen Chapter V, Section 3), but Lho catalytic decomposition of ncctylcno over copper ut somewhat higher temperatures lias been observed also (SI, 26, 27, 33, 34). Man ganese (SJ) was found to promoto acetylene decomposition above 480. Most of these reactions were accompanied by hydrogenation and lho appearanco of traces of oily condensation products of acetylene. In many coses particles of tho metab became distributed throughout the carbon deposits, so that coating of lho metal with curium did not completely stop Die catalytic cITcct. Metals other than those montionod above appear to have little effect on the rate of decomposition of acetylene (8). Tho effect