June 16, 1916. THE COLLIERY GUARDIAN. 1135 grab is independently controlled from a cabin at the top of the vertical frame, and can discharge about 550 tons per hour. This type of machine was more particularly introduced for discharging iron ore, but an important equipment is in operation for discharging coal at Fort William on the northern (Canadian) shores of Lake Superior. Loading Steamers. Loading the steamers at the coal shipping ports at Lake Erie is mostly accomplished by hoist tips or, as ;thcy are termed in the States, car dumpers. Unlike the 'usual coal hoists in this country, the cars are turned ■almost completely over sideways and discharged through 'the top, instead of being tipped endways and emptied from the end doors of the. wagons, which is the system iprevhiling here. Fig. 10 shows a typical form of car •damper in use at the Great Lake ports. The carload of 'coal is discharged entirely into the receiving chute, from which it passes into a square section telescopic trunk or delivery chute suspended down the hold of the vessel. Fig. 9.—Box Car Loader, Screening Tower, and Cranes. This trunk usually consists of four telescopic sections, the top and smallest of which is about 3 ft. by 3 ft. It is kept full of coal when loading, and the flow is con- trolled by movement of the trunk at an angle across the hold, or by telescoping the sections; so that after the trunk is first filled, when commencing to load, there is no fall of coal into the hold, and the direction of delivery- can be altered by means of a hinged trimming attach- ment at the lower end of the trunk. This telescopic delivery trunk is a special feature of the car dumper, and is controlled separately from the hoisting and dumping, a cabin being situated as shown on the illustration near the top of the trunk and right over the hold of the vessel being loaded. The subject is such an extensive one, and only a brief reference io it has been attempted herein. Sufficient has, however, been mentioned to indicate the enormous tonnage of coal dealt with at the Great Lake ports and to show that the importance of mechanical discharging storage and distributing equipment has been realised. The Future of Tar Products. — Before the Wales and Monmouthshire District Gas Association at Newport, Mr. J. H. Canning read a paper on this subject, in the course of which he said all authorities agreed that the decay of the coal tar industry in England was due to the apathetic atti- tude of all classes towards science, owing to insufficient scientific education. Scientific teaching should be added to our too-literary schemes of study, with early specialisation of promising scientific students on methods mere fitted to qualify them for the actual practical work of life than has often been the case, and to enable them to conduct independent research. In the next place, better prospects must be opened up before well trained engineering and chemical talent. The Hoechst Chemical Works had 307 chemists out of a staff of 9,016 in 1912, and we could only hope to regain the chemical tirade from Germany by thoroughly training our own men in the proper way, and paying them adequately when they were duly qualified. After the lack of scientific education and of skilled technologists’, the next great obstacle to . our progress was the defective state of our Patent Law. Germans had habitually filed dummy patents simply to prevent British subjects making any use of the processes described. In 1906-10 no less than 561 German patents for synthetic dyes and intermediate products were filed, as against 30 English. Another obstacle had been the extreme unwillingness of the Excise authorities to permit of a cheap supply of industrial alcohol. The Minister of Munitions had, for the time being at least, solved this problem. We were likely to be faced, at the end of the war, not only by organised German effort, but also by so many other problems consequent upon the war, that there would be very little time to improvise plans for winning back our former supremacy, and in any case schemes devised in a burry were seldom of much use. It was supremely important, therefore, that the gas industry, which was so vitally interested in the recovery of a branch of trade almost infinite in its possibilities, should take prompt action, if necessary in union with other interests, to urge upon the nation the absolute necessity for the removal of old obstacles, and the provision of new facilities in order that we might once more come by our own. THE ABSORPTION OF OXYGEN BY COAL.* By T. F. Winmill, B.A., B.Sc. Part VIII.—The Effect on Absorption of Size of Coal Particles, and Percentage of Oxygen in the Air. In a previous’paper ) it was shown that the rate of absorption of oxygen by coal is neither directly propor- tional to the surface area of the coal exposed nor to the percentage of oxygen in the air. Further experiments are now described supporting this conclusion. Effect of the Size of the Coal Particles.—The earlier experiments showed that the absorption is not simply proportional to the outer surface of the coal-dust. In the present series much coarser coal was used, the coal •being broken just to pass'a two-mesh sieve, and any fine I> KI w i: ' M ?'t___A.- Fig. 10.r—Car Dumper for Shipping Coal. coal made in the breaking being removed over a 10-mesh sieve. The experimental method was essentially the same as that described in the previous papers, but much larger coal samples (as a rule, about 12 lb. in weight) were used. The rates of absorption of oxygen found are recorded in Table I. :— Table I.—Rates of Absorption of Oxygen in Cubic Centimetres per 100 grammes for Coal just passing THROUGH A 2-MESH Si EVE. Hours. Barnsley Hards Barnsley Softs Barnsley Hards at 30 degs. C. at 30 degs C. at 50 degs. C. 1 3'4 2'2 8'05 2 3'2 21 7'75 4 28 1’9 7'2 6 2’5 1’75 6'7 8 2'25 1’6 6'2 12 1'85 1'4 5'3 18 T5 1'2 4'25 24 T3 1'1 3'4 30 115 1'05 2'85 36 IT 10 2'5 48 095 0'95 2T5 72 0'8 0'8 1'65 96 0'7 0’7 1'35 * From a paper read before the Institution of Mining Engineers. f Trans. Inst. M.E., 1913, vol. xlvi., p. 576. For the purpose of comparison, it may be assumed that when the coal-dust is fine enough to pass a 200-mesh •sieve, it shows practically its maximum rate of oxygen ■absorption. The figures set forth in Table I. can then be expressed as percentages of the maximum rate., and in I his way a more direct comparison of the effect of the size of the coal particles on the rate of oxygen absorption c:i a be obtained. Table II—Rate of Absorption for Different Fine- nesses of Coal Expressed as Perceatages of Rate for Finest Dust. Barnsley Hard coal. A Barnsley Softs at 31 degs. C At 3 i degs. Cent. AtSO’C. Hour f Passing s. a 30- but Passing a 10- but Passing a 2- but Passing a 2- but Passing a 2- but 2 left on a 60-mesh sieve. ... 77 left on a 30-mesh sieve. 67 ... left on a 10-mesh sieve. 17 left on a 10-mesh sieve. 15 left on a 10-mesh sieve. 10 4 ... 80 70 ... 19 22 11 6 ... 77 72 ... 21 31 12 8 ... 80 69 23 54 13 12 ... 82 70 ... 26 37 15 18 ... 83 72 ... 27 37 17 24 ... 80 73 ... 27 38 20 36 80 74 ... 30 38 23 48 ... 82 74 30 40 24 72 ... 79 72 ... 31 41 28 96 ... 79 74 ... 37 40 3') It appears from Table I that in a given ti me coarse coal will absorb less oxygen than fine coal dust: but from Table II. it is clear that as time goes on the difference in the rates of absorption becomes somewhat less, indicating that, after a very long time, the total quantity of xygen absorbed by coal is practically independent of the state of division. It follows, therefore, that the same total quantity of heat will be produced ultimately by ths atmospheric oxidation of either lump coal or coal dust. The rate < f production of heat is, however, so very much .••.lower from the former than from the latter that the heat produced has every chance to become dissipated and so avoid any increase in the temperature of the coal. Any subsequent regrinding of- the coarse coal much increases the Tate at which oxygen is absorbed. The curve connecting absorption and time is some- what flatter in the case of the coarser coals, but the characteristic shape remains very much the same as for the finest dusts. It is, however, clear that the rate of oxidation is not simply proportional to the outer surface of the coal particles. The comparison can be made in one or two ways—either from the rates of oxidation after each sample has absorbed a definite quantity of oxygen (that is, the samples are equally “ fresh ”), which is perhaps the more correct theoretically, or by comparing the progressive rates of oxidation stated in Table IT. Table III.—Comparison of Rate of Oxidation of Coal and Size of Coal Particles. Passing Particulars. sieve. Approximate ratio of surfaces ........ 100 Ratio of absorption on equally “fresh ” samples ......... 100 Average ratio of ab- sorption during the first 96 hou's .. 100 Passing Passing Passing a 30- but a 10- but a 2- but left on a left on a left on a 60-mesh 3 '-mesh 10-mesh sieve. sieve. sieve. 20 7’5 P7 60 .. 40 6 80 72 27 Obviously, then, the oxidation is not a simple surface action : the oxygen in some manner penetrates the coal particles. The state of division of the coal has clearly a most important bearing on the possibility of spontaneous beating. Other factors being equal, it appears that coal dust is far more likely to originate combustion than lump coal, and it is owing to the favourable conditions set up by the grinding of the coal and the regulation of the air supply that fires so often start in breaks in the coal. Effect of Variation in the Oxygen Percentage in the Air on the Rate of Absorption.—It is to be expected that a reduction of the percentage of oxygen in the air will also reduce the rate of absorption by the coal. It has been shown previously that with “ fresh ’’ coal the effect produced on the absorption is not directly proportional to the reduction in oxygen percentage, for, when the oxygen percentage in the air was reduced to 8, the rate of absorption was still 65 per cent, of that in normal air containing 20;9 per cent, .of oxygen.* In the case of coal which had been exposed to the air for some time, the following were found, the results being expressed in arbitrary units, since comparative figures only were required :— Table IV.—Comparison of the Rates of Absorption of Oxygen by Coal passing through a 60-mesh Sieve for different Oxygen Percentages. Temperature 30 degs. Cent. ; Barometer, 760 mm. Percentage of oxygen in air. 5 Comparative rate of absorption of oxygen. 12 10 18 15 22 21 (normal air) 25i 40 34 60 42 80 50 100 58 With coarse coal passing a two-mesh but left on a 10-mesh sieve, the rates of absorption showed exactly the same variation as with the fine dust. The effect of reducing the oxygen percentage in the air is to reduce the rate of absorption of oxygen by the coal, but not in simple proportion, percentage having to be reduced to 5 before the rate falls to half that in normal air. Since any moderate decrease affects the rate of absorption very * See Trans. Inst. M.E., 1913, vol. xlvi., p. 574,