September 11, 1914 ______________________________________________________________________________________________________ 564 THE COLLIERY GUARDIAN. The counterweights in the inclines run underneath the tubs, and the ropes are passed round two cast iron drums, fitted with a band brake and mounted on oaken framing. The brake mechanism is hoisted to the top of the incline by means of a hand winch and steel rope running over pulleys at the two ends of the incline. The junctions between the brake inclines and the gate roads are expensive to establish in these steep seams, it being necessary to drive a by-pass round, at about 10 ft. from the incline (fig. 9); and therefore it has been found preferable in some cases to adopt special measures. For example, in one vertical seam (6^ to 7 ft.) with good roof and floor, the return airway was converted into a brake incline by cutting into the rock on one side and then packing up the original airway, as shown in fig, 10. This method enables the junctions to be made without extra cost, thus counterbalancing the increased expense of the incline; and, moreover, the incline is in better condition and the timberings are left unaffected by the removal of all the coal. In another seam, which is very thin and where the inclines and junctions would there- fore be very costly to make, small cross-headings are driven through to the inclines of the adjacent seam, about 20 yds. away. This is cheaper than the con- struction, timbering, and upkeep of separate inclines and junctions in this thin seam; and this practice is being extended to other groups of seams. (To be continued.) ___________________________ Hull Coal Imports;—The effect of the war is reflected in the diminished consignments from the collieries to Hull during August. According to the return compiled by Mr. W. Herbert Truman, coal inspector to the Hull Corporation, 228,623 tons were delivered in August—30,820 tons by water and 197,803 tons by rail - as compared with 642,771 tons in August 1913. Imports in the eight months ended with August amounted to 4,114,219 tons, as compared with 5,451,024 tons in the corresponding period of 1913. Coast- wise shipments from Hull in August aggregated 50,783 tons, making the total for the year so far completed, 525,675 tons. To foreign ports 191,038 tons were exported, as against 414,297 tons, making the total for the year 2,247,468 tons, as compared with 2,964,665 tons in the corresponding period of last year. Exports in August, according to country of destination, were as follow:— Aug., Aug., Country. 1914. 1913. Tons. Tons. Aug., Aug., Country. 1914. 1913. Tons. Tons. Africa . 5,337 America, S.. ..14,698.. . 30,986 Canada .... .. 2,604.. — Austria .. — 308 Belgium .. 2,278.. . 7,378 Denmark ., ..12,319.. . 12,750 East Indies. .. 280.. — Egypt .. 4,746.. . 9,949 France .. 6,280.. . 16,959 Germany.... .. 9,828.. . 76,068 Holland .... ..31,589.. . 43,352 Italy ....... 1,709... 11,232 Jersey and Guernsey ... 895... 1,079 Portugal ... 1,600... 2,291 Russia, N. ...64,749.. 154,160 Spain ______ — ... 1,740 Norway .....10,110... 12,355 ..... Sweden ......27,048... 27,607 Turkey ........... — ... 746 West Indies 305... — Exports and Imports of Coal Tar Products.—The follow- ing shows the values of coal tar dyes imported into the United Kingdom in August and the eight months ended therewith :— August. Jan.-Aug. 1913. 1914. J913. 1914. Alizarine and anthracene «£<£<£<£ dyestuffs ........... 17,695... 3,439... 166,680.131,970 Aniline and n phthalene dye stuffs______________ 118,999. 21,572 .. 1,027,006...94<»,273 Synthetic indigo ........ 8,353... 1,457... 52,583... 48,971 Other coal tar dye stuffs.. — ... — ... 562... 154 The quantities imported in August were as follow:— Alizarine and anthracene dye stuffs, 580 cwt.; aniline and naphthalene dye stuffs, 4,085 cwt. ; synthetic indigo, 449 cwt. The values of the coal products exported in August were as follow:— August. Jan.-Aug. t 1913. 1914. 1913. 1914. Coal products, not dyes : £ £ £ Aniline oil and toluidine 109.. . 260.. 20,875.. . 18,736 Anthracene 70.. . 424.. 1,310 . 712 Benzol and toluol 19,687.. . 7,021.. . 212,967.. . 144,006 Carbolic acid 14,108.. . 3,846.. . 129,811.. . 83,207 Coal tar, crude 582.. 155.. . 11,293.. 7,461 Do. refined & varnish 6,433.. . 2,779.. . 44,159.. . 42,402 Naphtha 1,411.. 564.. . 15,095.. . 15,311 Naphthalene 941.. . 400.. . 24,331 18,845 Pitch 18,268 . 3,833.. . 744,192.. . 598,846 Tar oil, creosote, &c 75,191.. .25,616.. . 450,971.. . 398,661 Other sorts 18,345.. . 8,030.. . 210,122.. . 181,423 » 1 Total 155,145.. .52,928.. .1,865,126.. .1,509,610 Coal tar dye stuffs 12,080.. . 6,121.. . 116,247.. . 117,009 The following quantities of the above products were exported in August:—Coal products, not dyes : Aniline oil and toluidine, 8,711 lb.; anthracene, 214,205 lb.; benzol and toluol, 157,342 galls.; carbolic acid, 4,373 cwt.; coal tar, crude, 1,156 cwt.; coal tar, refined and varnish, 119,815 galls.; naphtha, 12,832 galls. ; naphthalene, 1,226 cwt. ; pitch, 38,471 cwt.; tar oil, creosote, &c., 1,434,261 galls.; other sorts, 21,892 cwt. Coal tar dye stuffs, 1,788 cwt. Exports of sulphate of ammonia are also shown :— Jan.-Aug. August. To 1913. 1914. <£ £ Germany............... 12,303... 987... France.................. 4,045... 966... Spain and Canaries.... 43,557... 34,439... Italy.................................. 4,604... 1,9<>7... Dutch East Indies____ 22,185... 35,74°... Japan ................. 146,263... 91,464... U.S. of America ........... 15,672... 15,416... British West India Islands (including Bahamas) & British Guiana............... 4,164... 2,201... Other countries ...... 50,412... 24,776... 1913. 1914. £ £ 68,825... 43,087 100,180... 26,105 615,632... 610,879 67,159... 42,556 428,759... 431,791 922,704... 808,028 188,909... 288,797 94,816... 83,578 409,385... 266,623 Total... _______ 303,205 207,905.2,896,36b..2,601,544 The following quantities were exported in August:— Germany, 81 tons; France, 84 tons ; Spain and Canaries, 3,054 tons ; Italy, 161 tons ; Dutch East Indies, 3,401 tons ; Japan, 8,088 tons ; United States, 1,363 tons ; British West Indies, 199 tons; other countries, 2,228 tons. The Absorption of Oxygen by Coal.* By T. F. WINMILL, B.A., B.Sc.f Part II.—The Quantity of Oxygen Absorbed. In Part I. of this investigation! some experiments were described having as their object an investigation into the factors affecting the rate of absorption of oxygen by coal, rather than a determination of the total quantity of oxygen which could be absorbed. It was, however, found possible to calculate approximately the volume of oxygen absorbed by 100 grammes of coal at 30 degs. Cent., and the following results were obtained for sub- stances from the Barnsley Bed in the Doncaster area :— Cubic centimetres. Hard coal ____________________ 760 Soft coal ____________________ 830 Cannel coal ________ ________ 587 Jacks__________________________ 560 Shale __________________________ 169 In order to obtain an independent confirmation of these results, an experiment was made, differing in principle and method from those already described. In the previous experiments a current of air was passed over coal maintained at 30 degs. Cent., and from an analysis of the issuing air stream the quantity of oxygen absorbed was calculated. In the present experi- ment coal was sealed up in a flask with air, and oxygen was automatically supplied to the flask to take the place of that absorbed by the coal. The apparatus was so constructed that the quantity of oxygen supplied to the flask could be measured, and in this way the total quantity absorbed by the coal in any given time could be determined directly. The apparatus used is shown in fig. 1. A glass tube A, 2 cm. in diameter and 30 cm. in length, supported horizontally, served as an oxygen reservoir. It is con- nected at the one end with a large bottle B, and at the other with the rest of the apparatus. It was made of this form so that oxygen might be supplied from it at a pressure very close to atmospheric, whether the reser- voir were full or nearly empty. The oxygen in A was confined over a 50 per cent, caustic potash solution of a density of 1-5. The total change in pressure for the delivery of the 100 cu. cm. of oxygen contained in A is therefore— 20 x 1*5 o.o p —— = 2*2 mm. of mercury, which is a very small variation from the initial pres- sure. A glass tube C of a" capacity of 110 cu. cm. is connected with a mercury reservoir, and serves as a constant volume burette. It was surrounded by a water jacket, of which the temperature was known. By closing the requisite taps and opening that on C, the oxygen could be drawn at any time from A into C and measured, without disturbing the rest of the apparatus. D contained a small quantity of strdhg sulphuric acid, just covering the end of the inlet tube, so that no dif- fusion of gas from F into A could take place. A barometer tube E served to measure the pressure in F, the reaction flask in which the coal was confined. This was completely immersed in a thermostat maintained at 30 degs. Cent. ± deg. during the course of the experiment. The apparatus having been fitted up, 28-30 grammes of hard coal ground to pass through a 200-mesh sieve were placed in F, together with 10 grammes of freshly ignited potassium hydroxide, so arranged as not to come into contact with the coal. The neck of F was then sealed, the tap b closed, and a mercury pump sealed on to /, and started working. After the air had been removed from F, the gas drawn off by the pump con- sisted of about 90 per cent, of methane for the first two days, the remainder being nitrogen. jVfterwards the complexity of the hydrocarbons increased, whilst the quantity decreased. Of the 2 cu. cm. of gas per day obtained on the fourth and fifth days, about 50 per cent, consisted of hydrocarbons, approximating in composi- tion to propane. By the seventh day the combustible gas evolved was butane. The quantity of these higher hydrocarbons was, however, very small in comparison with the methane obtained, and would not perhaps total 1 per cent, of the methane. For the last three days the quantity of gas obtained was very small (0-3 cu. cm. per day), and consisted mainly of nitrogen. On the 10th day, therefore, the flask F and the tube E were filled with air at atmospheric pressure. The tap F was then closed and b opened, so that, when the coal in F absorbed oxygen from the air in the flask, an equal volume of oxygen entered from a, thus keeping the atmo- sphere in F of constant composition. The volume of oxygen in A was measured from time to time by the method already described, the difference between the two measurements at times t1 and t2 giving the quantity of oxygen absorbed in the interval t2 — t1. After 60 days the rate of absorption of oxygen by the coal became very small indeed. The tap b was then closed, the pump started again, and the whole of the air from F, the gauge E, and the trap D pumped out, measured, and analysed. In Table I. the quantity of oxygen absorbed by the coal after various intervals is recorded. In the third column are given the similar figures calculated from the experiments described in the previous paper. ________________________________________________________ * Papers read before the Institution of Mining Engineers. t Chief Chemist at the Doncaster Coal Owners’ Research Laboratory. I Trans. Inst. M.E., 1913, vol. xlvii., p. 563. Colliery Guardian, September 26, 1913, p. 625. Table I.—Quantity of Oxygen Absorbed by 100 Grammes of Barnsley Hard Coal at 30° Cent. After Cubic centimetres From previous Days. absorbed. experiment. - 1 99 ...... 210 2 165 302 3 226 376 5 279 476 7 325 560 10 378 630 15 462 702 20 529 736 25 590 745 30 647 754 50 756 — 60 781 — x 800 760 To the final figure in the second column an addition has to be made, for the air pumped out from F (402 cu. cm.) at the end of the experiment showed a deficiency of 10 cu. cm. of oxygen, and contained also 0*5 cu. cm. of hydrocarbons and 2-1 of carbon monoxide. The oxygen deficiency is probably due to the evolution of nitrogen from the coal at the beginning of the experi- ment—a point which has already been mentioned. The corrected result is therefore :— 800 4- j + 1) X = 840 cubic centimetres. 28'3 The number deduced in the previous paper was less than this, but, allowing for the nature of the extra- polation in the first series of experiments, the two results are in very fair agreement. It will be noticed that although the final results confirm one another, there is a considerable difference in the rate of absorp- tion in the two series. This is most probably due to the different states of the coal in the two experiments. In the one now described the coal was absolutely dry, having been kept in a high vacuum over freshly ignited potash andlcalciumL chloridelfor a considerable time. In the other, rhe coal was in*an atmosphere saturated with moisture (derived mainly from the water content of the coal itself). It would appear, therefore, that there is a very considerable difference between the rate of absorption of oxygen by absolutely dry coal, and that by “ wet ” coal, although the total quantity absorbed is the same in both cases. This is in agreement, so far as the change in velocity is concerned, with the obser- vations of Mahler,* but is the reverse of that found by Richters. Whilst it is unsafe to argue by analogy as to the effect of moisture on the rate of oxidation of coal, until more is known of the nature of the reaction, yet it may be stated that it is in accordance with general chemical experience that atmospheric oxidations are as a rule much accelerated by traces of moisture. This must not be taken to mean that a wet place in a mine is neces- sarily more liable to spontaneous heating than is a drier place in the same mine. All coals contain a sufficiency of moisture in themselves, ample enough to render them “ wet ” in a chemical sense. Any extra quantity of water is more liable to prevent spontaneous heating than to accelerate it, by virtue of the fact that it is constantly evaporating from the coal surface, and so exercising a cooling effect. It has already been mentioned that 2-1 cu. cm. (or 0-53 per cent.) of carbon monoxide was found in the air in F after the oxidation, and this quantity has been formed in the presence of an abundant supply of oxygen. Roughly, one part of carbon monoxide appeared for every 100 parts of oxygen disappearing. This is especially noteworthy, for carbon monoxide is never found to an appreciable amount in the normal return air of a mine, whereas from this experiment it would be expected that where the return air contains 20 per cent, of oxygen or less, at least 0-01 per cent, of carbon monoxide should be present, a quantity which would be detected easily by the delicate blood test. Mr. P. Mahler, in the paper already referred to, states that carbon monoxide is a normal constituent of mine air to a mean value of 0-002 per cent. The results that he gives, however, appear to be somewhat uncertain : for, so far as can be judged from the published table, the maximum quantity of carbon monoxide was always found in the intake air of the pit; The fact that there was an oxygen deficiency in the air pumped out from F after the experiment, although the evacuation had been continued for a long time, and to a pressure of 0-1 mm., shows that there is no adsorp- tion (as distinct from absorption) of oxygen. If there had been any adsorption, it is to be supposed that some oxygen would have been given up from the coal at this high vacuum, and there would have then been an oxygen excess instead of a deficiency. In any case, the first fractions of the air removed would have been poorer in oxygen than the last fractions, but this was not so. It must be concluded, therefore, that a true chemical reaction takes place between the oxygen and the coal, and this conclusion is, of course, confirmed by the fact that so much heat is evolved during the absorption. In Part I. it was shown that there is a very pro- longed oxidation of coal even at low’ temperatures, and this point is brought out again in the present experi- ment. The table shows that, even after 60 days, when the coal is in a very fine powder indeed, the reaction is not finished, but is still proceeding at such a rate that if no heat w’ere lost by the coal its temperature would rise by about | deg. Fahr, per day, and this effect is, of course, cumulative. It is in this property that the * “ Experiences sur 1’Oxydation de la Houille,” by P. Mahler, Annales des Mines, 1913, vol. iv., series 11, p. 163.