498 PRING: THE DIRECT UNION OF CARBON AND

LIV.-The Direct Union of Carbon and Hydrogen at High Temperatures. Part II.

By JOHN NORMAN PRING.

THE question of the direct union of carbon and hydrogen, which formed the subject of a previous paper by the author in con- junction with R. s. Hutton (Trans., 1906, 89, 1591), has recently received a good deal of attention. In the paper just cited, the synthesis of acetylene at relatively very low temperatures (from 1850O upwards) was established, but the investigation of the formation of methane at lower temperatures gave less decisive results, and all that could be said was that the reactivity of the carbon diminished with continued use, and that the presence of impurities increased the methane formation, probably by catalysis.

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HYDROGEN AT HIGH TEMPERATURES. PART 11. 499

As the temperature was raised in approaching the acetylene stage, and above this temperature, an increase in the methane was observed, which may be explained by the decomposition of the acetylene and the well-known greater stability of methane.

The present work is intended, by still greater precaution in the purification of the reacting substances, and by approaching the equilibrium stage from the opposite side, to clear up some of the outstanding points of uncertainty, and particularly to ascertain the equilibrium values of methane in the system methane, hydrogen, and carbon over a large range of temperatures.

Bone and Jerdan (Trans., 1897, 71, 41; 1901, 79, 1042) first announced the possibility of obtaining methane by the direct union of carbon and hydrogen at 1200O. The percentage of methane obtGined in these experiments varied frGm 0.7 to 1.4, mean 1.26.

Berthelot (Ann. Chim. Phys., 1905, [viii], 6, 183) disputed the above results, and emphatically expressed his belief that no hydro- carbons are produced at 1200-1350°, provided that the reacting materials are subjected t o an exhaustive purification.

Mayer and Altmayer (Ber., 1907, 40, 2134) investigated the methane equilibrium in the system methane, hydrogen, and carbon. Hydrogen was allowed to react with carbon, to which nickel was added to serve as a catalyst. Experiments on the direct formation and on the decomposition of methane were made between the temperatures 470° and 620O.

In the thermodynamical equation : CH ET = - 18507 + 5,9934 TlOg2' + 0.002936 T2 + R T l o g ~ (ad2'

as expressed by Haber, which gives the equilibrium ratio of methane to hydrogen at all temperatures, the constant R was found by Mayer and Altmayer to be 21-1. A t 1200" (1473O abs.) this gives the value of 0.07 per cent. for methane.

The experimental work is not, however, at all conclusive, as analyses of the gases show amounts of nitrogen varying from 2 to 20 per cent., and the percentages of carbon monoxide are not published.

H. von Wartenberg (Zeitsch. anorg. Chem., 1909, 52, 299) investigated the cyanogen, hydrocyanic acid, and aoetylene equili- bria, but his experiments were carried out in a very rough manner, and he only extended the work to exceedingly low concentrations of acetylene. In criticising the work of the present author and Hutton, Wartenberg overlooks t.he fact of the decomposition of acetylene into methane, and points out the anomaly of acetylene which is endothermic and methane which is exothermic both increasing in quantity a t the higher temperatures.

VOL. XCVlI. L L

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500 PRING: THE DIRECT UXION OF CARBON AND

Bone and Coward (Trans., 1908, 93, 1975) extended the earlier work of Bone and Jerdan, and claimed finally to have proved the direct union of carbon and hydrogen by the conversion of given weights of carbon into a practically quantitative yield of methane. Although it seems probable that the conclusions of Bone and Jerdan and Bone and Coward, that carbon unites directly with hydrogen t o form methane, will be upheld, the fact that in their experiments the carbon was always in contact either with some known catalyst or with porcelain, which, by reduction, might yield a catalytically active compound, fully justifies the further investigation of this reaction, which, moreover, is essential before concluding that direct union occurs.

For these reasons it was thought desirable, in the course of the present investigation, t o adopt means to carry out the purification of the carbon to the highest possible degree, and to use hydrogen in the purest and driest condition, so as to eliminate any possible complication through the presence of carbon monoxide and nitrogen. It was also thought it would be of interest to investigate different kinds of carbon in their behaviour towards hydrogen. The varieties studied were retort carbon, sugar-charcoal, and graphite.

The method employed was similar to that used in the earlier work (Pring and Hutton, Zoc. cit.), and consisted in the use of a rod of carbon, or of a graphite tube provided with a narrow slit along the top, and inside which could be placed the variety of carbon it was desired to study. These rods or tubes, which could be heated to any desired temperature by the passage of an electric current, were suitably mounted at a considerable distance from the glass walls of the containing vessel, and all contact of the heated parts of the carbon with any substance but the surrounding hydrogen was avoided.

The temperature of the carbon rods, in this manner, is sur- prisingly uniform, and can be readily estimated by means of a Wanner optical pyrometer.

A tubular glass flask, of 24 litres capacity, formed the reaction vessel, as shown in Fig. 1. The tubes CC, of brass or copper, were stopped at PP with brass plugs by brazing. Graphite pieces DU were inserted by mere contact in holes bored in the brass plugs, and the graphite supported the carbon rod or graphite tube K. A slow circulation of water through the metal tubes by means of the tubes ww during the heating of the rods sufficed to keep the former quite cold. No visible heating of the graphite end pieces was ever observed, whilst the temperature of the rod was uniform to within 2 or 3 mm. from these supports. The metal tubes were fitted gas-tight a t A and B by soft wax, which was occasionally

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HYDROGEN AT HIGH TEMPERATURES. PART 11. 501

coated over with a solution of collodion in alcohol. These wax lutings allow the tubes a little play during the expansion of the rod by heat and remain perfectly gas-tight under these conditions, even when the flask is completely evacuated. The leak of air into the vessel seldom corresponded with more than 1 mm. when the flask was kept for one day under 1 cm. pressure. A charcoal tube was fitted at T, which could be cooled by liquid air, and thus complete the exhaustion of the vessel. Before each series of experiments, this exhaustion was allowed to proceed for a few hours, and the rod kept a t a temperature of about 1500O in order to dry the inside walls of the vessel as completely as possible and remove any occluded gas or final impurity from the carbon. The outlet tube f1 was to enable a

E'JG. 1.

b u Y

preliminary partial exhaustion of the apparatus by a water pump, and the outlet F led to a mercury gauge and to a Topler mercury pump, where a more complete exhaustion could be effected or samples of gas withdrawn from the vessel for analysis. The hydrogen used in these experiments was generated by the electro- lysis of baryta solution. The baryta was for this purpose recrystallised several times, and the electrolysis conducted in a large U-tube placed in a hot-water bath, a current of about 3 amperes being used. The hydrogen was then passed through a heated Jena combustion tube filled with copper gauze, a small heated tube filled with platinised asbestos, and then through a calcium chloride tube. Two methods were then at different times used far further purifica- tion of the gas.

A. After leaving the calcium chloride tube, the hydrogen was L L 2

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502 PRING: THE DIRECT UNION OF CARBON AND

passed through a spiral glass tube, cooled on the outside by liquid a,ir. The air ,in the drying tubes was first displaced by passing a current of hydrogen through for several hours, and allowing to escape through a side-tube, which dipped under mercury. The hydrogen was then admitted through the tap M , which could be carefully regulated, into the vacuous globe.

B. The gas was filtered through a specially constructed palladium tube, making use of the well-known permeability of this metal to hydrogen when slightly heated.

The tube was of the form shown in Fig. 2 at X, the total length being 30.5 cm., external diameter of wide part 5 mm., and of narrow part 2 mm., thickness of walls 0.5 mm., weight 14.2 grams. The tube was connected to the glass a t A by means of rubber valve tubing, which was then covered with pressure tubing.

The palladium was encased in a Jena glass tube, actual contact with the glass being avoided by a palladium bridge at B. The

PIG. 2.

I 1

glass tube was surrounded by an electrical wire resistance furnace R, whereby a temperature of 350-400° could be conveniently main- tained. The outlet tube S was sealed on to the tube V (Fig. 1). By opening the tap M (Fig. l ) , the palladium tube could be evacuated together with the flask, and, on warming, perfectly pure hydrogen diffused through and gradually filled the vessel. The rate of diffusion varied, of course, with the pressure inside the flask. With the palladium tube at 400°, when the vessel qas vacuous, about 20 c.c., and with a pressure of 60 cm. about 5 c.c., entered per minute. It was never necessary to fill the vessel entirely, as the subsequent heating of the rod expanded the gas to atmosphere pressure.

Temperature Readings.

It was found by comparison with a thermo-element (H. C. Green- wood, Trans., 1908, 93, 1486; Proc. Roy. Soc., 1909, 82, A , 402) that the particular pyrometer used is accurate within 20° at 1250O when sighted on to the outside of the carbon rod, and that at

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HYDROGEN AT HIGH TEMPERATURES. PART 11. 503

1550°, 1670°, and 2000O there is not a departure of more than 15O for (‘ black body ” radiation. Consequently, the only error of any magnitude which could arise at these temperatures would be due to departure from (‘ black body ” radiation, and this deviation in the case of carbon is known to be small. I n the experiments described below, the pyrometer was calibrated against a thermo- element a t 1200°, and then frequently checked by means of an amyl acetate lamp.

Analysis of Gas.

The estimation of the small quantities of methane in the previous work (Pring and Hutton, Zoc. cit.), which was effected in a Sodeau apparatus, without a preliminary condensation of the hydrogen, was a matter of some difficulty on account of the tendency to form oxides of nitrogen on exploding the gas with excess of oxygen.

The presence of acetylene was ascertained qualitatively by the formation of cuprous acetylide, but in the quantitative estimation, by the use of bromine or fuming sulphuric acid, no means were adopted to distinguish between the acetylene and ethylene or any other unsaturated hydrocarbon.

I n the work now described, a condensation of the hydrogen was usually first made by means of palladium foil in cases where no unsaturated hydrocarbons were present. I n this way, 1000 to 1500 C.C. of the resulting gases were condensed to 50-100 c.c., and thus an accuracy of from ten to thirty-fold in the methane estimation was obtained. Samples of gas which contained un- saturated hydrocarbons, in addition to methane, were not condensed by palladium, but were analysed as follows: The gas was first treated with a solution of ammoniacal silver chloride to remove acetylene. Two separate lots of this reagent were used, the last being freshly prepared, to ensure complete removal of this gas. A treatment with bromine or fuming sulphuric acid, followed by potassium hydroxide solution, was then carried out, t o remove ethylene. The carbon monoxide was then removed by two treatments with ammoniacal cuprous chloride solution, and the methane estimated by exploding with an excess of oxygen and measuring the carbon dioxide.

Purification of Carbon.

The method employed by Bone and Jerdan and Bone and Coward (Zoc. cit.) for purifying the carbon consisted in igniting the finely divided substance for several days in a stream of chlorine, followed by hydrogen, at a temperature of 1100-1200°. The disadvantage

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504 PRING: THE DIRECT UNION OF CARBON AND

of this method lies in the improbability of evei- being able to remove the last traces of combined hydrogen, and the serious contamination which must result from contact with the containing vessel during the long period necessary for the treatment.

The methods adopted in the present investigation were as follows. A. I n the cases where amorphous carbon rods, usually of 0.4 cm.

diameter and 10 mi. long (retort carbon), were used, these were placed in a carbon tube furnace and treated for two to three hours with a current of chlorine at about 1500°, and then for about fifteen minutes with a current of nitrogen, and finally for two to three hours with a current of hydrogen. The carbon tube used for this furnace was 28 cm. long and 2 cm. external diameter. Elec- trical connexions were made at the end by graphite rectangular bars, and a current of 160 amperes at 11 volts was found to produce a temperature of about 1550O when charcoal was used as packing around the tube.

An analysis made of a rod after this purification showed the presence of less than 0.10 per cent.. of hydrogen and 0.05 per cent. of ash. After this treatment, the rod was mounted in the glass reaction vessel, being supported by the graphite end-pieces. It was here raised to a temperature of about 1500O by the passage of an electric current while the vessel was kept at a high vacuum by means of charcoal cooled by liquid air. I n some experiments a measurement was made, by means of a McLeod gauge, of the pressure inside the vessel under these conditions, and was found to vary from 0.01 to 0.10 mm. It was found possible to maintain this low pressure for an indefinite period. The carbon rod, which was heated for an interval of from one to five hours, received in this way a further purification, while an effective drying of the inside of the vessel was a t the same time ensured.

In addition to the above treatment, great importance is attached to the fact that the same rod was used continuously throughout a large number of experiments, after each of which the heating in vacuum was again repeated for a short time, and only the pure hydrogen was allowed to enter the vessel after each evacuation.

B. In the case of experiments with sugar-charcoal, the procedure consisted in gradually igniting sugar to a bright red heat, reducing the carbon to a fine powder, placing in a graphite boat, and treating this in the carbon tube furnace alternately with chlorine, nitrogen, and hydrogen, as described above for the rods. A tube was prepa'red from Acheson graphite, 9.5 cm. long, 0.95 cm. external, and 0.6 cm. internal diameter, and provided with a narrow longitudinal slit. This was subjected to a prolonged purification treatment, and then filled with the purified charcoal and mounted

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HYDROGEN AT HIGH TEMPERATURES. PART II. 505

in the glass vessel in the manner employed with the rods. In one series of experiments the carbon used was purified with even more rigour, by repeating the alternate treatment with chlorine, nitrogen, and hydrogen, at. 1550O for six times over a total period of six hours.

A disadvantage found with these tubes is that, unlike the case of the thinner carbon rods, the temperature is only uniform over a central region of about two-thirds of the tube, and from here it gradually falls off to the cooled supports. A t higher temperatures, however, this uniform zone extends over a somewhat greater length.

Another inconvenience with this method is that while the tem- perature of the tube is Geing raised, the finely divided carbon shows a curious tendency to disperse and be expelled from the aperture, even when this is very small. This scattering is much more marked when the heating is done in a vacuum, and in all cases necessitates a very gradual raising of the temperature.

C. For examining the reaction with graphite, the tube employed in the above experiments was used empty, having been purified by prolonged treatment with chlorine and hydrogen.

The procedure in an experiment was as follows. After the preliminary heating of the purified carbon in the evacuated reaction vessel, pure hydrogen wils admitted through the tap M (Fig. 1). The pressure of hydrogen could be measured by means of the mercury gauge connected to F, which also led to the pump L. The mercury gauge also served as an outlet for the gas during its expansion through the heating of the carbon. During the experi- ment the current employed was kept constant, and temperature readings were taken at frequent intervals by the Wanner optical pyrometer. A t the end of each experiment the gas was removed by a Topler pump and transferred to a graduated gas holder con- taining glycerol and water, and after measurement was condensed by palladium foil. Sixty grams of this foil, cut into small strips, were, for this purpose, placed in a 300 C.C. flask provided with a wide ground-glass stopper and a, sidetube wit4 a ground joint and mercury seal. The flask was exhausted by a Topler pump, and the gas from the holder then allowed to enter. The flask was heated by a water-bath to 80-100°, when absorption of the hydrogen was very rapid if the amount of carbon monoxide present was below 0.01 per cent. The residual gas was removed by the pump, measured over mercury, and analysed.

Tabulated List of Results.

Values for the methane, given to two places of decimals, denote that the analysis has been made on the uncondensed gas, whilst

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506 PRING: THE DIRECT UNION OF CARBON AND

the methane in the gas condensed by palladium has been estimated to three places. The same carbon was used throughout each series without, in any way, dismantling the apparatus.

Part l.--Reaction.s Examined in Presence of Carbon Monoxide.

A. Sugar-charcoal in graphite tubs.

Series 1.-Sample purified by heating once in chlorine, nitrogen, and hydrogen alternately for one hour at 1550°, and then for half an hour in a vacuum, a t 1200°, in the reaction vessel:

Order Product (percentage). Time of ex- I \

periment. Temperature. in hours. co . CH,. NP 1 1200-1250" 2 0.70 0-29 0.15

0.6G 0,247 -

A

2 1345 lit-

Series 2.-Sample of sugar-charcoal purified by heating alter- nately in chlorine, nitrogen, and hydrogen six times for six hours at 1550°, and then in a vacuum for half an hour before each experiment:

Order of ex-

periment. 1 2 3 4 5

6 -

Time Temperature. in hours.

1250 I*

1250 4 1500 14

1250"

1250 2 1250-1300 1

3 -

Product (percentage). A r \

co. CH4. N,. 0.87 0.400 -_ 0-6 0.4 0-3 0.35 0.279 - 0'36 0'198 - 0-87 0 '24 0'20 0.97 0-324 - 0.70 0.18 -

The above series clearly shows the diminution in the amount of methane formed after the first few times of use.

Series 3.-Sample of sugar-charcoal purified by heating five times alternately in chlorine, nitrogen, and hydrogen for five hours, and then in a vacuum as above:

Product (percentage). Order of Time -

0'8 0'106 1.8 0.143 2 161 5 1

3 1250 2 0.65 0-196

experiment. Temperature. in hours. co. CH,. 1 1230-1270" 19

The above series was conducted with the view of ascertaining if the heating of the carbon t o about 1600° wouid cause any marked diminution in the reactivity.

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HYDROGEN AT HIGH TEMPERATURES, PART 11. 507

B. Experiments with graphite :

Order of experiment.

1 6 5 7 3 4 5

Temperature. 1250" 1250 1250 1250 1325 1520 1720

Time in hours.

Product (percentage). I

CO. 0.15 0'01 0.13 0.25 0'18 1'3 2 '0

>

CH,. 0'143 0'046 0.232 0.252 0.170 0.172 0'246

Part 2.-Reactions Conducted with Very Low Concentrations o,f Carbon Monoxide.

Series 1.-Retort carbon.

Amorphous carbon rod purified by heating alternately in chlorine, nitrogen, and hydrogen for two hours at 1550°, and then in the reaction vessel in a vacuum at 1425O for two hours:

Order Product (percentage). of ex- / \

periment. Temperature. Time. CO. CH,. C,H,. C,H,. h

4 11 00" 34 hours 0'006 0.123 - - 6 1100 13 ,, 0'012 {~~~~~ - -

- - 1 1150 24 ,, 0-3 0.238 7 1200 50 mins. <0*01 0.150 - - 5 1200 5 hours 0.01 0.165 - -

18 1200 11 ,, <0'005 0'334 - - 0'15 0-160 - - 2 1300 1% $ 9

3 1300 4 ,) 0-01 0'220 - - 0-010 0.178 - - 8 1400 2 9 9

9 1500 2 ,, 0'04 0.168 - 11 1600 35 mins. 0.001 0.210 - c

10 1600 12 hours 0.02 0'240 - - 12 1725 1 hour ~ 0 . 0 0 2 0.354 - - 14 1770 15 mins. 0'32 0-402 15 1830 12 0.15 0'530 nil -

17 1950 30 mins. 0'44 0.86 0-20 0.22 19 2055" 10 9 , 0 '33 1'13 1'30 0.97

* Rod broke and arced for about three seconds a t end.

- - 13 1200 22 ), 0'01 0-342

-

- -

16 1850 1 hdhr 0.05 0.597 trace -

Series 2.-Amorphous carbon rod, heated as last one. 1 1570" 1 hour 0'160 0-154 nil nil 2 1620 80 niins. 0'087 0.181 3 2080 15 2 , 0 '35 1.08 0*;5 0 '45 4* 2180 11 9 9 0'10 2.18 1-80 1-72

* Rod arced for about three seconds at end

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508 PRING: THE DIRECT UNION OF CARBON AND

Part 3.--Decomposition of Acetylene and Methane in Presence of an Excess of Hydrogen at R g h Temperatures.

Experiments on the decomposition of these hydrocarbons were undertaken to attempt to decide to what extent methane might arise at the higher temperatures as a secondary action from the decomposition of acetylene, to measure its stability at these tem- peratures, and, if possible, t o find the final equilibrium value of methane from the other side.

Acetylene was for this purpose prepared by dropping ethylene dibromide into hot alcoholic potash, washing the gas with alcohol, and collecting over water.

About 5 litres of this were condensed by liquid air and then allowed to evaporate, the middle portion being passed into a holder of about 200 C.C. over mercury. From here it could be admitted into the reaction vessel through the tap A', the connecting tube having first been evacuated, together with tlie vessel. Methane was prepared by decomposing commercial aluminium carbide with dilute hydrochloric acid, washing the gas well with ammoniacal cuprous chloride to remove acetylene and hydrogen sulphide, and then liquefying the methane, vaporising, and collecting the middle fraction.

Small percentages of acetylene or methane could in this way be admitted into the reaction vessel, which was then filled with hydrogen. An amorphous carbon rod was used. Samples of gas were withdrawn from the reaction vessel before and after each experiment. In some cases condensation with palladium was resorted to. The results are tabulated below:

EX- pcriment. Temperature.

1 1480"

2 1200°

3 1775"

4 1200"

5 1580"

6 1200" to 1620"

Time. 0 1 hour 2 hours 48 ) Y

0 I& hours ;4 ) Y

J )

0 10 mins. 1 hour 0

25 hours 0 2 hours 0 2 hours

Composition of gas.

CO. CH,, C,H,. C,H,. - - 0.6 - 0-15 0'32 nil trace 0'2 0'26 Y ) Y Y

0.25 0.25 9 ) Y Y

- - 3.50 - 0.27 4'20 0.50 0-85 0'41 1 '41 nil 0'35 0'48 1 .oo > ) 0.55 - - 20.2 -

0'08 5.93 5-02 1'13 0.09 0.77 nil nil - 6 '00 0-073 4'63 -

-- 5.0 0.05 1 *75 - 6-73

0'25 5-47

A fl -.

- - -

- - - -

-- - - -

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HYDROGEN AT HIGH TEMPERATURES. PART 11. 509

Experiment in which 5 per cent. of carbon monoxide was added, to study its effect on the decomposition of methane:

- - 1200" 0 5 *O 6 -5 - -

7 3 hours 4'2 5 '92

__ - 64 3.72 5 *95

Part IV.-AmrpJLous Carbon Rod with a Deposit of Platinum orb Surface to Assist the Reaction Catalytically.

This rod was purified in chlorine, nitrogen, and hydrogen at the same time as the previous ones, and was coated with a thin deposit of platinum by electro-deposition, and then heated in the reaction vessel in a vacuum a t 1300O for half an hour. Pure hydrogen was then admitted, and the experiment conducted it9 usual. In the experiments in column B a small percentage of methane was admitted to find the equilibrium from the decomposition.

A. Product (percentage).

Order of - experiment. Temperature. Time. GO. CH,.

1 about 1050" 1& hours 0.052 0.866 2 ) ) 1100 ;4 9 ) 0.007 0.690 8 1200 7 7 0.011 0.540 3 about 1300 30 mins. 0.014 0.340 6 1500 45 > ) nil 0.297

B.

Decomposition of methane with same rod. 1175- 1200" 0 - 2 '31

4 hours 0.006 1-14 1200 0 - 1 '95

1500 0 - 3 '2 0.003 0.594

'2 7 ) 1 -03 0 *330

12 9 a

Conclusions.

The experiments described above clearly show that pure carbon combines directly with pure hydrogen at all temperatures above 1100O. At 1200O the velocity of the reaction is so slow in the absence of any catalyst that the estimation of the exact equilibrium value of methane is somewhat uncertain. An experiment extend- ing over twenty-two hours at 1200O seemed, however, to yield the limiting value of 0-35 per cent. of methane, although this could not be confirmed by approaching the equilibrium from the other side, as the decomposition of small amounts of methane by pure carbon at 1200O proceeds even more slowly than the synthetic reaction.

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510 PRING: THE DIRECT UNION OF CARBON AND HYDROGEN.

A t 1500O an equilibrium value of 0.17 per cent. of methane appeared to be approached within about two hours, although even at this temperature the decomposition of methane was too slow to serve for the evaluation of the equilibrium quantity. More definite equilibrium values were obtained by using carbon which contained a surface deposit of platinum. In this case, in experiments at temperatures between 1050O and 1500°, the reaction was very much accelerated, and the same percentage of methane was finally obtained whether its formation or its decomposition was

Synthesis of hydrocarbons from pwc amosphous Methane equilibrium with carbon. illaxiinwn amounts obtained. platinum coated carbon.

x Sfyntlu&s of methane. o Decomposition of methane.

investigated. The amount formed was 0.55 per cent. at 1200°, and 0-30 per cent. at 1500O.

Above 1550O the percentage of methane began to rise with the temperature. These increased quantities of methane do not, at these temperatures, necessarily represent equilibrium values, but probably arise from the decomposition of acetylene, although the amount of the latter gas present was too small to be detected below 1850O.

Experiments on the decomposition of hydrocarbons showed that acetylene changes quickly to methane and ethylene above 1500°, and that the methane formed is comparatively stable. This behaviour is similar to the decomposition which hydrocarbons

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COLOUR AND CONSTLTUTION OF AZO-COMPOUNDS. PART V. 511

undergo at lower temperatures (Bone and Coward, Trans., 1908, 93, 1197).

In the decomposition of acetylene a t 1 200-1400°, ethylene was also formed, and found to persist; consequently, this appears to preclude the possibility of the methane arising secondarily in the experiments at these temperatures, as, in these cases, no trace of ethylene was found in the gas.

Graphite and sugar-charcoal showed a similar behaviour to amorphous retort carbon in its reactivity with hydrogen.

The presence of carbon monoxide seems to have no effect on the final equilibrium in the synthesis or decomposition of methane a t any temperature employed, or on the velocity of the reaction. The synthesis of acetylene could not be taken to the equilibrium stage, as with methane, in the form of apparatus used. Acetylene, being endothermic, is stable in larger amounts the higher the temperature, and would consequently undergo some decomposition in passing away from the heated carbon through the intermediate zones of temperature of the outside layers of gas.

The equilibrium values obtained in the above work probably refer to systems of different concentrations than the surrounding gases, on account of a probable condensation of gas on the surface of the carbon or catalyst. This problem is now being investigated by the use of high gaseous pressures and the examination of the effect of catalysts other than platinum.

In conclusion, I wish t o express my indebtedness to Professor E. Rutherford for the facilities he has extended for conducting this research, and to Dr. R. S. Hutton for suggesting the work, and for his continued interest and assistance during its progress.

ELECTRO-CHEMICAL LABORATORY, THE UNIVERSITY,

M ANCHE~TEH.

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