26 BONE AND CAIN: THE EXPLOSION OF ACETYLENE II.-Tlze Explosion of Acetylme with less than its own volume of Oxygen. By WILLIAM ARTHUR BONE and JOHN CANNELL CAIN. IN TRO D u CT 10 N. DURING the past three years, the authors have carefully studied the gaseous products formed when acetylene is exploded with less than its own volume of oxygen, a subject which up to the present has received very little attention. In 1892, Lean and Bone showed that when ethylene is exploded with less than its own volume of oxygen, the greater part of the hydrocarbon undergoes a partial combustion in accordance with the following equation C,H, + 0, = 2CO + 2H, whilst some of the excess of ethylene is decomposed at the high tem- perature of the explosion, forming methane and acetylene, together with a deposition of carbon, It seemed interesting t o compare the explosion of acetylene with that of ethylene under similar conditions, in the first place because acetylene is a characteristic endothermic compound, and is readily decomposed by shock into its elements, with the evolution of much heat ; secondly because this hydrocarbon has played a prominent part in recent discussions on the subject of the luminosity of flame; and finally because acetylene may now be pre- pared on a commercial scale from calcium carbide, and will probably be extensively used as an illuminant.Acetylene differs from methane and ethylene by the readiness with which it explodes when mixed with comparatively small volumes of oxygen. Methane will not detonate unless it is fired with nearly its own volume of oxygen; Lean and Bone showed that ethylene must be mixed with about 65 per cent.of its own volume of oxygen before itWITH LESS THAN ITS OWN VOLUME OF OXYGEN. 27 can be fired under ordinary conditions, On the other hand, a mixture of acetylene with from one-fifth to one-fourth its own volume of oxygen forms a mixture which when sparked explodes with the utmost violence; consequently the authors have been able to study the explosion of acetylene with from about 25 to 100 per cent. of its own volume of oxygen. The mixtures were exploded in a long leaden coil, at the atmospheric pressure, in a manner to be described in detail later; the chemical changes occurring were, therefore, those of the explosion wave. The results of our work may be briefly stated as follows.1. When acetylene is exploded with less than its own volume of oxygen, carbon monoxide and hydrogen are finally obtained owing to the partial combustion of the acetylene in accordance with the equation C,H, + 0, = 2 0 0 + H, the cooled products of the explosion in the coil being under consider- able pressure. 2. The excess of acetylene is for the greater part resolved into its elements by the shock of the explosion wave. A small quantity of acetylene (as much as 1 per cent. in some cases) is, however, found in the products of explosion. This may be due to acetylene which has escaped decomposition altogether, or possibly to a recombination of carbon and hydrogen in the rear of the explosion wave. The authors have not been able to detect the presence of any other unsaturated hydrocarbon in the products of explosion.3. Methane does not appear to be formed when acetylene is exploded with less than its own volume of oxygen, a t any rate not in any appreci- able amount. The authors have very carefully investigated this point, and although some of their earlier experiments led them to suspect the presence of a small quantity of methane (some 0.5 per cent.) in the products of explosion, a more rigid examination has left no doubt in their minds that methane is absent. This is particularly interesting, seeing that when ethylene is ex- ploded with less than its own volume of oxygen, methane is produced, in certain cases to the extent, of 6 per cent. of the whole products. The difference in the two cases is probably due to the fact that acety- lene is readily resolved into its elements by shock, whilst in the case of ethylene the excess of hydrocarbon which escapes combustion is subjected to a ‘‘ roasting ” process, and thereby decomposed into carbon and methane.4. Small amounts of a gas absorbable by solid potassium hydroxide were invariably found in the products of explosion. This was in part, if not altogether, due to the presence of carbon dioxide, for when28 BONE AND CAIN: THE EXPLOSION OF ACETYLENE the products of explosion were aspirated through a clear solution of baryta, a white precipitate of barium carbonate was formed. This was shown by firing a small volume of each mixture in a short eudiometer made of very stout glass. I n the case of mixtures containing acetylene mixed with less than three- quarters of its own volume of oxygen, a thick deposit of carbon formed, but where mixtures contained a larger proportion of oxygen much less carbon separated.EXPERIMENTAL. Pvepcwutiom of the ikixtwes. Pq*epm*cctioln of Acetylene.-The acetylene used in these experiments was prepared by the decomposition of ethylene dibromide by an alcoholic solution of sodium ethoxide, as follows.* 50 grams of sodium were dissolved in about 500 grams of alcohol (methylated spirits rectified by distillation over quicklime answers the purpose very well), and the solution introduced into the round- bottomed flask A (Fig. 1) (capacity = 1 litre) which was immersed in 5. Carbon was deposited. €3 C * This method for the preparation of acetylene was devised by V.Meyer and F. Marsden (Marsden, Imnug. Dissert., Heidelberg, 1892).WITH LESS THAN ITS OWN VOLUME OF OXYGEN. 29 a water bath, and fitted with a long reversed condenser B and a tap funnel C. As soon as the contents of A were boiling vigorously, the ethylene dibromide was allowed to drop in gradually from C ; it was then readily decomposed by the sodium ethoxide in A, acetylene and vinylic bromide being evolved, The volatile products of decomposition passed off through the condenser B, kept cool by a rapid stream of water, a considerable quantity of the vinylic bromide condensing and running back into A. The gas then passed through two cylindrical wash-bottles, D, each containing about 30 C.C. of alcohol, and surrounded by a mixture of ice and salt ; here a further quantity of vinylic bromide condensed.After leaving D, the gas passed into two Winchester pint bottles, E.E, about three-quarters filled with a freshly-prepared am- moniacal solution of cuprous chloride, where the acetylene was rapidly absorbed. At the conclusion of the experiment, the copper acetylide was allowed to settle, the supernatant ammoniacal liquor was poured off as completely as possible, and the copper compound washed by decan- tation with cold water ; it was finally filtered and washed a t the pump, and preserved for future use in a moist condition. The mixtures of acetylene and oxygen were made in a glass gas holder over mercury in the following manner. A quantity of moist copper acetylide capable of yielding about 1; to 2 litres of acetylene was introduced into a strong round-bottomed flask A, Fig 2.Dilute hydrochloric acid was then dropped on t o FIG. 2. the paste from the tap funnel, B, and on gently warming the flask, a steady current of acetylene was evolved. The gas passed through the washing cylinder, C, two-thirds full of a concentrated solution of potas- sium hydroxide, and then through a three-way tap, D, into t,he atmo-30 BONE AND CAIN: THE EXPLOSION OF ACETYLENE sphere outside the laboratory. As soon as all air had been expelled from the apparatus, the gas was sent into the graduated glass gas holder, E (capacity = 1,800 c.c.), previously filled with mercury from the reservoir, F. The latter was so arranged that it could be gradually raised or lowered a t will, so that the gas might be collected in E at as nearly as possible atmospheric pressure.When about a litre of acetylene had been collected, the tap, a, leading into the reservoir was shut, and the rest of the gas sent through D into the atmosphere. After about an hour, the levels of the mercury in E and F were equalised, and the volume of bhe gas in E read. Oxygen generated by heating pure potassium chlorate in a hard glass tube, and passing the gas evolved through a layer of cotton wool and then through a wash-bottle containing a strong solution of potas- sium hydroxide, was now added to the acetylene in E until a mixture of the desired composition was produced. The gases were allowed to stand for several hours in order that they might thoroughly mix, and then samples for analysis were collected over mercury.Explosiocn of the Mixtuws.-As mixtures of acetylene and oxygen explode with great violence, it was necessary to carry out the opera- tion in a leaden coil. The coil A, Fig. 3,s metres long and of an internal diameter of 13 mm. (capacity about 700 c.c.) was immersed in a bucket of cold water, a stout glass firing piece, B, being attached to the coil by means of Faraday cement. Each end of the coil was closed by d FIG. 3. C strong steel taps,a, 6, and communication was made through b and a glass tail-tap, c, with ct mercury manometer, C; the latter served to indicate, as will be afterwards shown, the presmre in the coil after anWITH LESS THAN ITS OWN VOLUME OF OXYGEN. 31 explosion, By means of the tail-tap, c, a direct connection could be made with the outside atmosphere instead of with the manometer, so that the products of explosion could be readily drawn off for analysis.Before making an experiment, the coil was thoroughly tested to see if all the joints were tight, by exploding a mixture of coal gas and air in it. The inside of the coil was then thoroughly dried by boiling the water in the bucket, and blowing a good current of dried air through the coil for several hours. The water in A was then allowed to cool, or was syphoned off and replaced by cold water from the mains, the air current through the coil being maintained meanwhile. The mixture of acetylene and oxygen mas introduced into the coil by attaching the gas holder to the end a and raising the mercury reservoir; then on opening the taps b and c the air was expelled from the coil.After about a litre of the mixture had been passed into the coil, the exit gases from c were found to be highly explosive, but another half-litre of gas was sent through the coil in order that there might be no doubtas t o its being filled with a gaseous mixture of the same composition as that originally made in the gas holder; the tapcc was then closed, and a few moments later the tap b. Thus the coil was filled with gas at the ordinary atmospheric pressure. The tap c was then turned so as to bring the coil in connection with the manometer, and the mixture was fired by an electric spark a t B. I f the various joints had successfulIy resisted the shock of the explosion, the coil and its contents were allowed t o stand for a quarter of an hour in order that they might cool down to the temperature of the surrounding water, and then, by opening the tap b, connection with the manometer, C, was made, and the pressure of the gases in the coil read off; in every case, a considerabIe i n c r e m e in pressure was observed.Finally samples of the products were drawn off through c and collected in tubes over mercury ; these samples were subsequently carefully analysed. The rest of the products were displaced by a current of air and sent through an ammoniacal solution of silver chloride. I n every case a precipitate of silver acetylide, identified by the usual method, mas obtained, showing that the products of explosion contained free acetylene.Ancilysis of the Gases.-The apparatus at our disposal for this part of our work was a modified form of the McLeod apparatus (described in Phil. T r a n s . , 1884, Part 11.). This consists of a eudiometer connected at its base by means of a gun-metal three-way tap with a barometer on the one hand, and a mercury reservoir on the other, the latter being so arranged that it could be raised or lowered as occasion required. Both eudiometer and barometer are water-jacketed, and by keeping a good stream of cold water direct from the mains running32 BONE AND CAIN: THE EXPLOSION OF ACETYLENE through the jackets, the temperature in the apparatus could be kept quite constant throughout an analysis. The upper end of the eudio- meter is connected by means of a glass capillary tube with a laboratory vessel, standing in a trough over mercury, into which the gases are sent for purposes of absorption.Both eudiometer and laboratory vessel are closed by glass taps, and careful experiments showed that the amount of gas left in the capillary tube between these two taps after each absorption was sufficient to appreciably affect the result of an analysis. The authors, therefore, at the outset of their work carefully determined the amount of gas left in the capillary for varying amounts of gas treated in the laboratory vessel, and from their results were able to draw up a table of corrections to be applied in any case. This correction amounted to about 0.1 volume for every 50 volumes of gas treated in the labora- tory vessel, and the various numbers given in the sequel are readings so “ corrected.’’ Before each analysis, the eudiometer was washed out, first with dilute sulphuric acid, and then several times with distilled water.The readings were made by artificial light, using a telescope fitted with cross-wires, and placed at a distance of 1.6 metres from the apparatus. T?ie O~igincd Mixtures.-After trying several methods for the analysis of a mixture of acetylene and oxygen, the authors finally adopted the following as by far the most satisfactory. A measured volume of the mixture under investigation was thoroughly mixed in the McLeod apparatus with from 10 to 12 times its own volume of air, previously freed from carbon dioxide by standing over solid pot,assium hydroxide. The mixture was then exploded, when, if a large excess of air had been added, a thin pale flame travelled down the eudiometer without causing any appreciable shock, and was not accompanied by any liberation of carbon. The advantage of this method is that the percentage of acetylene present in the original mixture may be determined from two data, namely, (1.) from the contraction, C, in volume which occurs on explosion (due to the water formed). (2) From t h e absorption, A, which occurs when the products of explosion are treated in the laboratory vessel with a solution of potassium hydroxide, as is readily seen from the equation C,H, + 240, - - 2C0, + H,O Y-’ 3+ volumes on cooling become 2 volumes.L- _-u Thus the acetylene = -2 C or -; A. The residual gases were then allowed to stand over an alkaline solution of pyrogallol in the laboratory vessel for one hour, in orderWITH LESS THAN ITS OWN VOLUME OF OXYGEN.33 that the excess of oxygen might be removed ; the residual nitrogen was then measured. Subtracting the amount of nitrogen present in the air added in the earlier part of the analysis, the amount of nitrogen in the original mixture could be determined. Having thus estimated the acetylene and nitrogen, the oxygen was determined by difference. The Pyoclucts of Explosion.-The products of explosion always con- tained small amounts of carbon dioxide, and of acetylene, possibly also some other unsaturated hydrocarbon *-the main constituents were, however, carbon monoxide and hydrogen. In order to determine the amounts of carbon dioxide and of acety- lene present in the products, a large measured volume of the gases was brought into contact with a ball of solid potassium hydroxide in the laboratory vessel of the McLeod apparatus, After the volume had been again measured, the gases were exposed in the laboratory vessel to a layer of pyrosulphuric acid for half an hour, in order athat all acetylene or other unsaturated hydrocarbon might be removed, then washed with a potassium hydroxide solution, and remeasured.For the further analysis of the products of explosion, a small measured volume of the gases, from which the carbon dioxide and acetylene had been removed in the manner already described, was mixed with an excess of air free from carbon dioxide, and exploded in the eudiometer of the McLeod apparatus.The contraction in volume, C, was determined, after which the gases were treated with a solution of potassium hydroxide in the laboratory vessel, and the absorption, A, estimated. The residual gas was then left in contact with an alkaline solution of pyrogallol for upwards of an hour, after which the volume of the residual nitrogen was read. Mixture A . This contained 100 volumes of acetylene to 29 volumes of oxygen. On exploding the mixture in the leaden coil in the manner described, an increase in pressure of 260 mm. was observed, the barometer being at 754 mm., and temperature of the water in the bucket, 15". A large quantity of carbon was deposited during the explosion. Analysis of the Uyigiml Mixtuye. Volume of mixture taken ........................ 62.5 Volume of air added .............................790.9 * The authors wish to state that in the case of two mixtures the amount of acetylene present in the products was estimated by a gravimetric as well as by the usual volumetric method ; the results agreed well, and therefore the presence of another unsaturated hydrocarbon is rather a reniote possibility. vor,. LXXI. D34 BONE AND CAIN: THE EXPLOSION O F ACETYLENE Volume of gas taken , . , , . . Volume of air added ...... Percentage C ......... Percentage A ......... Percentage nitrogen found Cj ................................................ 71.3 A ................................................ 95.2 Residual uitrogen, after absorption of excess of oxygen by alkaline pyrogallol.. .... 626.9 Nitrogen present in air added ..................625.6 ... Nitrogen originally present in mixture ... 1.3 i.e., 2 Ool0 11 5.50 469'00 104'00 44.50 - ] BIean 47.57 Calculated from C, Acetylene = 71.3 x Q = 47.53 9 9 9 , A, ,, = 95.2 x 8 = 47.60 Taking the oxygen by difference we arrive at the following percentage composition of the mixture. Acetylene. Oxygen. Nitrogen. 76.0 22.0 2.0 Leaving the nitrogen out of the question, this corresponds to a mixture of 100 volumes of acetylene with, as nearly as possible, 29 volumes of oxygen. Analysis of the Products of Explosion. a. Determination of the cas.bon dioxide, ncetplene, &c. Volume of gas taken Absorption by solid KOH ........................ Absorption on treatment with pyrosulphuric Hence carbon dioxide = 0.25, and acetylene, &c.= 0-56 per cent. b. Analysis of the Residucd Gases a f t w mnzoval of cadon dioxide, acetylene, &c.-Three analyses were made, the first two with gas from the same sample tube, and the third with gas from a second tube ; the last gave a slightly different result from the other two. In the following table we shall state the volume of the gas taken for each analysis, but in order that the results of the three may be readily compared at a glance, we shall state the contraction in explosion, C, and the absorption by potassium hydroxide after explosion, A, in volumes per 100 volumes of the original gases-terming these numbers percentage contraction and absorption respectively. ........................... 323.2 0.8 acid and KOH ................................. 1.80 109'00 ' 104.60 4;;::; 1 437'20 104'31 104'88 43'80 1 '00 1-33 ~~ Mean._____ - - 104.40 44-27 1'16WITH LESS THAN ITS OWN VOLUME OF OXYGEN. 35 Calculating from the above results, we shall see that there is no sign of the presence of any saturated hydrocarbon, such as methane, for instance, in these gases. For if x = volume of hydrogen present, and 9 = volume of carbon monoxide, Then 3x/2 + y/2 = 104.40 and y = 44.27 Solving these equations we get x = 54.85. Hi!. co. N2. Total. 54.85 44.2 7 1.16 100*28. Now if methane or any other unsaturated hydrocarbon had been present in fair quantity, say 1 per cent,, and we had calculated from the above figures on the hypothesis that only hydrogen, carbon monoxide, and nitrogen were there, our figures would have totalled up to much more than 100.As a matter of fact they sum np to 100.28, and this excess of 0-28 is no doubt due to error of experiment, prob- ably in the estimation of the nitrogen, which is very apt to come a little high in an analysis of this kind. If we include now the whole of the resuIts for the analysis of the products of explosion we obtain the following numbers. Therefore the residual gases contain CO,. C2H2. H2* co. N,. Total. 0.25 0.56 54.42 43.90 1.15 100.28 Mixtum E. This contained 100 volumes of acetylene to 328 volumes of oxygen, so that the two gases were mixed in the ratio of nearly 3 : 1 by volume. On exploding the mixture in the leaden coil, a very slight leakage at one of the joints was observed, caused, no doubt, by the violence of the explosion, This leak was at once repaired, and as the manometer still indicated an increase in pressure of nearIy 150 m.m., the mishap did not vitiate the experiment so far as the analysis of the products of explosion was concerned.A large quantity of carbon was deposited during the explosion. Ancclysis of the Origirzccl Mixture. Volume of mixture taken ..................... Volume of air added ........................... 49.10 473-40 C ............................................ 54.50 A ............................................. 72-00 Residual nitrogen after absorption of ex- cess of oxygen by means of alkaline pyrogallol .................................... 375.6 0 236 BONE AhtD CAfN: THE EXPLOSION OF ACETYLENE Nitrogen present in air added ...............374.5 Nitrogen originally present in mixture . , . Calculated from C, Acetylene = 54.5 x - - 36*33} Mean 36.16 Calculated from A, Acetylene = 72.0 x 8 = 36.00 Taking the oxygen by difference, we get the following for the per- centage composition of the mixture. Acetylene. Oxygen. Nitrogen. 73.65 24.1 1 2.24 Leaving the nitrogen out of the question, this corresponds as nearlyas possible to a mixture of 100 volumes of acetylene with 329 volumes of oxygen. A?zcclysis of the €3-oducts of Explosion. Volume of gas taken ........................... 160.9 2.4 Absorption by pyrosulphuric acid and KOH.. 1 *5 1.1 0 = 2 -24 o / o a. Deternzination of carbon dioxide, cccetylene, &c. Absorption by solid KOH ............... .,. ... Thus carbon dioxide = 1.49 per cent., and acetylene = 0.93 per cent.b. Analysis of the Residual Gases aftel* vemovnl of carbon dioxide, acetylene. -Two analyses were made of these residual gases, with the following results, which agree very closely. I. IT. Mean. Volume of gas taken .... '73*70 103.35 - Volume of air added .... 296.80 349.05 - Percentage C ...... 99.04 99.47 99.26 Percentage A ...... 49-79 49-35 49.57 Percentage Nitrogen ... 1 -03 1.00 1.01 Calculating from these, if x = percentage of hydrogen and y = per- centage of carbon monoxide, we have 3x12 + 912 = 99.26 y = 49.57 from which x = 49.65 and y = 49.57. That is, the residual gas contains H,. co. N, . Total. 49.65 49.57 1.01 100.23 which shows that no methane or other hydrocarbon of the series C,H,,~, is present.From the foregoing analysis we have calculated the percentage composition of the products of explosion to be as follows. CO,. C,H,. H,, co. N,. Total. 1.49 0.93 48.45 48.83 0.98 100.23WITH LESS THAN ITS OWN VOLUME OF OXYGEN. 37 94.00 395.50 92'23 55.42 2.50 Mixtuve C. This contained 100 volumes of acetylene to 55 volumes of oxygen. After exploding the mixture in the leaden coil an increase in pressure of nearly 300 mm. was observed. The barometer stood 752 mm. and the temperature of the water surrounding the coil was 15". Analysis of the Original Mixture.-Two analyses were made with the following results. I. 11. Volume of gas taken ............ 62.20 59.00 Volume of air added ............ 702.95 719.30 C .............................. 58.45 55.20 A ..............................79.60 74-30 Percentage of nitrogen found ... - 3.00 109 *80 422.50 92.35 55-01 - From these numbers we get - I. IT. Mean. 62'40} 62-60 Percentage of acetylene from C... Percentage of acetylene from A . . . 62-38 62.95 62.65 Taking the oxygen by difference, we get the percentage composition of the mixture. Acetylene. Oxygen. Nitrogen. 62.60 34-40 3.00 This corresponds t o a mixture of 100 volumes of acetylene with nearly 55 volumes of oxygen. Analysis o f the Products of Explosion. a. Determimtiosa of carbon dioxide, ucetylene.-Two analyses were made with the following results. I. 11. Volume of gas taken ............ 175.9 175-8 Percentage of carbon dioxide ... 0.51 0.56 Percentage of acetylene ......... 1 -08 1.20 We may therefore my that the products of explosion contained as nearly as possible U.5 per cent.of carbon dioxide, and 1-15 per cent. of acetylene. b. Ancdysis of the Residuul Gnses clfter wmoval of cccdon dioxide and ucetyZene.-Three analyses were made with the following results, Volume of gas taken ..... Volume of air added ..... Percentage C . . ......... Percentage A.. ......... Percentage nitrogen found I. 1 1 1 . I 111. 120'25 426'30 92.08 55-13 2 *oo Mean. - 92-21 55.19 2-1538 BONE AND CAIN: THE EXPT,OSION OF ACETYLENE Calculating in the same manner as in previous experiments, we get for the percentage composition of the residual gases the following. H,. co. N,. Total. 43.07 55-19 2.15 100.41 and the percentage composition of the products of explosion CO,. C,H,. H,. co. N,.Total. 0.50 1.15 42.37 54.29 2.10 100.41 Mixtuye D. This contained 100 volumes of acetylene to 81.5 volumes of oxygen. On exploding the mixture in the coil, an increase in pressure of nearly 350 mm. mas observed, the barometer standing at 769 mm.; the temperature of the water surrounding the coil was 16". The mixture was analysed with the following results. Volume of mixture taken.. .... 62.9 Volume of air added ............ 692.1 c .............................. 51.1 A .............................. 67.8 Calculated from C, Acetylene 34.07 Calculated from A, Acetylene 33.90 Mean .................. 33.98 or 54.0 per cent. The nitrogen was determined in a separate experiment, and was Taking the oxygen by difference, we arrive found to be 2 per cent. at the following percentage composition of the mixture.Acetylene. Oxygen. K itrogen. 54.0 44.0 2.0 and leaving the nitrogen out of the calculation, this corresponds with 100 volumes acetylene to 81.5 volumes oxygen. Analysis of the Y~oducts of Explosion. a. Detew&nation of the ccwbon dioxide ccnd acetylene. Volume of gas taken ........................... Absorption by solid KOH ..................... 187.25 1 *65 0.20 Absorption by pyrosulphuric acid and KOH This gives us as nearly as possible 0.90 per cent. of carbon dioxide b. Ancdysis of the Residual Gases clfiei* 9.enaovcd of cicr6on dioxide and 0.1 per cent. of acetylene. C6nd acetylene.-Two analyses were made with the following results.WITH LESS THAN ITS OWN VOLUME OF OXYGEN. 39 I. I. 11. &lean. Volume of gas taken .........94.00 103.90 - Volume of air added ......... 349.00 408.00 - Percentage C ............ 80.85 80.27 $0.56 Percentage A ............ 67.10 67.19 67.14 Percentage of nitrogen found - 1-23 - Calculating from the above results, we obtain the following per CO,, C,H,. H,. CO. N,* Total. 0.90 0.10 31.01 66-47' 1.25 99.73 centage composition of the products of explosion. 11. I HI. Mixture E. This contained 100 volumes of acetylene to as nearly as possible 95 volumes of oxygen. On exploding this mixture in the coil, an increase in pressure of about 370 mm. mas observed, the barometer being a t 766 mm., and the temperature of the water in the bucket 12". Analysis of the 01.igincd itfixture. Volume of gas taken .......................... 75.5 Volume of air added ...........................670.4 C ............................................. 56.2 A ............................................. 76.4 5 3 1 -5 Residual nitrogen.. ............................... Acetylene { Nitrogen = 1.35 or 1.80 per cent. From these results, we obtain calculated from C 37.5 calculated from A 38.2 Taking oxygen by difference, we get Acetylene. Oxygen. Nitrogen. 50.00 48.20 1 .so Gas taken ....................................... Absorption by Pyrosulphuric Acid and Absorption by solid KOH .................. KOH. 310.7 308.0 322.0 1 '2 1 '1 1'2 0 '3 0.4 -40 BONE AND CAIN: THE EXPLOSION OF ACETYLENE. Volume of gas taken ...... Volume of air added ...... Percentage C ......... Percentage A ......... Percentage nitrogen found From these numbers we calculate that the gases contained 0.37 per cent. of carbon dioxide, and approximately 0.1 per cent. of acetylene. b. Analgsis of the Residud Gchses cifter ~eirzovcd of c a ~ b o ~ ~ dioxide ccnd ncet9lene.-Three analyses were made 2s follows. 134.6 - 110*00 119'75 415'45 441 -20 444'3 - 80.86 80.84 80'00 80'55 68'20 68'37 68.34 68'30 0.77 0-84 0 '85 0'82 1 I. I 11. I 111. I Mean. Ratio Acetylene : Oxygen in mixtnre exploded. 100 : 29 Calculating from the above results, we get the following per- centage composition of the products of explosion. CO,. C,H2. H,. co. N2. Total. 0.37 0.10 30.78 67.98 0.82 100.05 We may tabulate the results of our experiments as follows. LOO : 32'5 No. of bfjxture. 1 A . I 1:. I C. I D. 1 E. 100 : 55 100 : 81'5 350 mm. 100 : 95 370 mm. ........... 0.56 . . . . . . . . . 54.42 .......... 1-15 Increase in pressure on explo- sion. !60 mm. 1'49 0'93 48-46 48'38 0'98 0.50 1-15 42-36 54.28 2.10 0.90 0'10 31.01 66'47 1'25 0.37 0'10 20.78 67.98 0-52 Total .................... 100.29 Whilst it follows from the above results that the main reaction occurring when acetylene is exploded with less than its own volume of oxygen may be expressed by an equation such as one of the following, C,H, + 0, = 2 0 + H, 2C,H, + 0, = 2CO + 2H, -+ 2C 3C,H, + @, = 2CO + 3H, + 4C, it must be admitted that some steam is also produced ; this is 100'24 300.39 99.73 100'05BONE AND JERDAK : DIRECT UNION O F CAREON AND HYDROGEN. 41 evident from the fact that the rat'io of the hydrogen to the carbon monoxide in the products is always less than the above equations require. 1Sloreover, it mould be very difficult to account for t h e presence of carbon dioxide in the products, were no steam produced. OWENS COLLEGE, l$ANOHESTER.