1246 __________________________________________ THE COLLIERY GUARDIAN. June 21, 1918. __________________________________ _______________________________________________________ The coal sample was then emptied out of the bottle, and allowed to air-dry in the laboratory for a period of five or six weeks. As another way of overcoming the aforementioned difficulty of the adsorption of the carbon-dioxide, the following experiment was carried out:—A weighed quantity of the air-dried sample was placed in the flask of an absorption apparatus similar to that used by the writer to measure the solubilities of gases in coal.* The gaseous contents of this were completely pumped out by means of a Geryk vacuum pump. Pure air was then admitted and oxidation allowed to proceed. The rate of oxidation of the coal could be calculated from the observed fall in pressure (a correction being applied for the carbon dioxide produced). When almost half of the oxygen originally present had been absorbed, the con- tents of the apparatus were completely pumped out and analysed. A similar experiment was carried out with another sample of the air-dried dust, to which, however, moisture had been added. The results were as follow:— Composition of gas mixture. _____________ ___________ r-*----------Carbon . dioxide fl o fl h g production 3S X* “ as per- Description. § § § § centage of O g O -g oxygen absorbed. P. cent. P. cent. P. cent. P. cent. Per cent. Moist coal ... 2'17 ... 0*38 ... 12*45 ... 85*00 ... 22 Air-dried coal . 0’28 ... 0’04 ... 19'19 ... 80’49 ... 12 Carbon Monoxide. It will be observed that quite a considerable quantity of carbon monoxide has been produced in the oxidation of this old coal. It would appear, therefore, that carbon monoxide should be a normal constituent (although only in small proportion) of the blackdamp formed solely from the oxidation of old coal. These experiments show clearly that even after coal has been exposed to air for over a year, the blackdamp resulting from the absorption of oxygen by the coal has nothing like the composition of that normally occurring in the pit from which the coal sample was obtained. It may be argued that one year is only a very short period in comparison with the age of the pit, and that after a number of years the carbon dioxide production may increase considerably. It may be mentioned, however, that the average composition of the blackdamp for the whole of a large pit in the South Yorkshire coalfield has not varied appreciably during the past four years, this blackdamp containing approximately only 5 per cent, of carbon dioxide. Moreover, it has already been shown that an appreciable amount of carbon monoxide is produced as a result of the oxidation of “ old ” coal dust, and for all experiments the ratio of carbon monoxide to carbon dioxide appears to increase slightly with the time of oxidation. If, therefore, it is assumed that after many years the blackdamp resulting from the oxidation of coal will contain a high percentage of carbon dioxide, it should be likewise assumed that it will also contain carbon monoxide in relatively large quantities. So far as the writer can ascertain from published analyses of samples of blackdamp taken from old workings where no heating has occurred, the amount of carbon monoxide found has been negligible, even though the carbon dioxide has formed as much as 17 per cent, of the blackdamp. In certain pits, however, where the carbon dioxide produced is low, the oxidation of coal may reasonably explain the origin of the greater quantity of the black- damp. On the other hand, where the percentage of carbon dioxide in the blackdamp is high, some other explanation must be sought. Results given in some of the earlier papers from the Doncaster laboratory show the rate of oxidation of the different carbonaceous materials comprising the Barnsley bed. A number of analyses were given, and from these the composition of the resultant blackdamp may be calculated. If this is done, it would appear that, if anything, a smaller percentage of carbon dioxide is produced than is the case with pure coal. Oxidation of Timber. There is still, however, the question of the oxidation of timber to consider as a contributory factor in the production of blackdamp of high carbon dioxide con- tent. It is well known that rotting timber gives off in its oxidation large quantities of carbon dioxide.f The results of experiments to illustrate this may be quoted. Wood shavings (from an old pit prop which had been thoroughly “air-dried”) were placed in a flask, a small quantity of water (10 cub. cm.) added, the flask sealed, and left for 10 days. In a second (similar) flask another lot of the shavings was placed, but without adding any water. After 10 days the samples were withdrawn and analysed, with the following results:— Moist wood Dry wood shavings. shavings. Per cent. Per cent. Carbon dioxide................ 17*38 ... 0'00 Oxygen ..................... 0*58 ... 20'86 Nitrogen..................... 82'04 ... 79'14 Carbon dioxide production as percentage of oxygen absorbed 82 ... — Some of the dry wood was transferred to another bottle—well soaked in a 10 per cent, zinc chloride solution for between two and three hours, the latter then poured off, and the shavings washed two or three times with water, the water being then drained off as well as possible. To the remainder of the dry wood in the flask about 5 cu. cm. of distilled water were added. Both bottles containing fresh air were then sealed off and placed in the thermostat at 30 degs. Cent. After 16 days the gases over the wood in each case had the following composition:— * Trans. Inst. M.E., 1916-1917, vol. Hi., p. 338. t Appendix C, by Dr. Haldane, to the “ Second Report of the Royal Commission on Metalliferous Mines,” 1914, Parliamentary Paper [Cd. 7476]. Moist wood treated with Moist wood zinc chloride untreated. solution. Per cent. Per cent. Carbon dioxide 0'24 10'37 Carbon monoxide .... 0'03 0'00 Oxygen 20'26 9’98 Nitrogen 79'47 79'65 Carbon dioxide production as percentage of oxygen absorbed 27 93'1 These latter results are interesting, showing that the zinc chloride solution, while pi eventing active (bacterid or fungoid) decomposition, nevertheless allows a certain degree of oxidation to go on—an oxidation which from the point of view of carbon dioxide production is very similar to that taking place in the case of old coal. Some of these experiments were repeated, in order that the resultant blackdamp might be tested for carbon monoxide, with the following result:— Moist sawdust oxidised for six days. Per cent. 18'57 0*12 0'00 81*31 86*7 is Carbon dioxide ................. Carbon monoxide ............... Oxygen ........................ Nitrogen .................................. Carbon dioxide production as per- centage of oxygen absorbed ..... In the event of moist timber becoming oxidised, it very evident that an enormous quantity of carbon dioxide (compared with the oxygen absorbed) may be produced,- and on the other hand the proportion of carbon monoxide produced is very small. Her din then lies a very probable explanation of the large proportion of carbon dioxide occurring in black- damp of certain pits. The blackdamp resulting from the oxidation of coal and other carbonaceous material will be mixed with that from the oxidation and decay of timber. If the conditions of the pit are favourable for the production of a large quantity of timber black- damp—that is to say, where the pit is very wet and well timbered—one would expect the influence of the gaseous products of the oxidation and decay of the timber to have a predominating influence on the composition of the blackdamp; in other words, the blackdamp will contain a high percentage of carbon dioxide. On referring to the interesting report of Prof. Cadman and Mr. Whalley to the Royal Commission on Mines, one finds that in most cases where the conditions in the pit have been favourable for the decay of timber, the normal blackdamp of that pit is rich in carbon dioxide. On the other hand, in the naturally dry and dusty pits in the South Yorkshire area a comparatively small quantity of carbon dioxide is found. Acid Water. The sixth possible cause of production of carbon dioxide in pits has not yet been considered. This is due to the action of waters strongly acid with sulphuric acid (produced by the oxidation of pyrites) reacting Class of workmen. (Underground day wagemen). Weekly wage, July 1914 (a). Weekly wage, August 1917. Afternoon and night shift men five days excluding bonus turn. Morning shift men six days. Afternoon and night shift men and morning shift men. s. d. s. d. s. d. Timbermen (day wage) 36 4 43 7 63 8 Rippers 33 3 39 11 58 3 Assista,nt timbermen 27 5 32 11 48 1 ,, rippers 27 5 32 11 48 1 Roadmen 29 6 35 5 51 9 Riders (over 18 years) 30 11 37 1 54 2 Hauliers (day rate) 31 2 37 5 54 11 ,, (night rate) (e) 29 10 35 10 54 11 Trammers (over 18 years) 26 0 31 2 46 9 Labourers 23 8 28 5 46 9 Ostlers 24 4 29 2 46 9 Underground enginemen :— Main haulage (adults) 26 6 31 10 46 9 Subsidiary haulage (adults) 24 8 29 8 46 9 Underground pumpmen:— Main pumps (adults) 26 3 31 6 46 9 Small pumps (adults) 23 9 28 6 46 9 Fitters 27 0 32 5 47 5 Electricians 27 10 33 5 48 10 Rope splicers 31 4 37 7 54 11 Masons 34 4 41 2 60 2 Pitmen 34 0 40 9 59 7 Shacklers and spragmen 23 4 28 0 46 9 Lamplockers 21 7 25 11 46 9 Lam plighters 22 1 26 6 46 9 Oilers (oiling sheaves, rollers, etc.) 22 1 26 6 46 9 Coal cuttermen 36 0 43 3 63 2 Airwaymen 31 3 37 6 54 9 Watermen (watering roads) 24 3 29 1 46 9 Cogcutters 27 8 33 3 48 7 Timberdrawers 30 8 36 9 53 9 Bottom cutters :— Cutting hard bottom ...1 32 6 39 0 57 0 Cutting soft bottom 29 0 34 10 50 11 Assistant bottom cutters 25 5 30 6 46 9 Sheaf men, rollermen and pulley men 28 6 34 2 50 0 Underground banksmen :— Leading 30 3 36 3 53 0 Assistant 28 0 33 8 49 2 Underground winding enginemen 32 0 38 4 56 1 Pipe men ’ 26 9 32 1 46 11 Rope changers 30 4 36 5 53 3 Shimmers (at pit bottom) 25 8 30 10 46 9 Jig hitchers (at top and bottom of incline; 28 0 33 8 49 2 Wallers in working face 24 10 29 10 46 9 (a) Sixty per cent, above the 1879 standard—i.e., the maximum percentage under the 1910 Conciliation Board agreement. . -rx (b) Based on the percentage at present operative, and which came into force from December 1, 1916 viz., 55*83 per cent, above the 1915 standard, equivalent to 133*75 per cent, above the 1879 standard. (c) Afternoon and night shift men : Five days and bonus turn. Morning shift men : Six days. (d) Did not receive the bonus turn in July 1914, but now do so. (e) Including allowance for dooring. with carbonates. Messrs. Haldane and Meachem* pointed out that if all the sulphur of the pyrites is oxidised to sulphuric acid and the latter all reacts with carbonate, the volume of carbon dioxide produced would be to that of oxygen absorbed in the proportion of 8 to 15—or the carbon dioxide production = 53 per cent, of oxygen. This will give rise to a blackdamp having the composition—carbon dioxide, 12'4 per cent.; nitrogen, 87'6 per cent. As a matter of fact, the probability is that, in the oxidation of iron pyrites, a certain amount of basic sulphate will be produced; hence the resultant blackdamp will have a smaller quantity of carbon dioxide than that just quoted. There is no doubt that in a damp pit containing a large quantity of pyrites—and especially if this is present in the finely-disseminated condition—blackdamp containing a moderately high proportion of carbon dioxide will be found. Conclusions.—The composition of blackdamp may vary considerably as a result of different contributory causes:— 1. Should the blackdamp occur solely from the oxidation of coal, it seems most probable that its composition will then be carbon dioxide, 5 per cent.; nitrogen, 94 per cent, to 94'5 per cent., with possibly per cent, to 1 per cent, of carbon monoxide (this question of the exact production of carbon monoxide is, however, being investigated further). 2. Should the blackdamp arise from rotting timber, the proportion of carbon dioxide will be very high, and may amount to as much as 20 per cent. 3. In pits where acid water is largely produced, owing to the oxidation of iron pyrites, the resulting blackdamp may contain about 12 per cent, of carbon dioxide. 4. Coal seams which are liable to give off carbon dioxide in large quantities along with firedamp, or by itself, will doubtless influence the composition of the blackdamp of the pit. A knowledge of the exact composition of the black- damp existing normally in a pit is essential if, by means of the chemical analysis of mine-air samples, it is attempted to discover the presence of heatings or to trace the history of such. * Trans. Inst.M.E., 1898-99, vol. xvi., p. 457. __________________ THE WAGES OF UNDERGROUND DAYWAGEMEN. A statement issued on behalf of the mine owners by Mr. Finlay A. Gibson, secretary of the Monmouthshire and South Wales Coal Owners’ Association, details the present wage position, compared with the wages paid in July 1914. According to this statement the per- centage operative in July 1914 was 60 per cent, (maximum) above the 1879 standard, and the percentage operative in June 1918 is 55'83 per cent, above the 1915 standard, or 133'75 per cent, above the 1879 standard. The weekly wage in 1914 is calculated on the average Weekly wage, June 1918, in- cluding War Bonus of 9s. from Sept. 17, Increase, June 1918, compared with July 1914. 1917 (b). Afternoon and Afternoon night shift and night Morning and morning shift men (c). shift men (d). ; shift men. s. d. s. d. | s. d. 72 8 36 4 i 29 1 67 3 34 0 ; 27 4 57 1 29 8 : 24 2 57 1 29 8 ! 24 2 60 9 31 3 1 25 4 63 2 32 3 ; 26 1 63 11 32 9 26 6 63 11 34 1 28 1 55 9 29 9 24 7 55 9 32 1 27 4 55 9 31 5 26 7 55 9 29 3 23 11 55 9 31 1 26 1 55 9 29 6 24 3 55 9 32 0 27 3 56 5 29 5 24 0 57 10 30 0 24 5 63 11 32 7 26 4 69 2 34 10 28 0 68 7 34 7 27 10 55 9 32 5 27 9 55 9 34 2 29 10 55 9 33 8 29 3 55 9 33 8 29 3 72 2 36 2 28 11 63 9 32 6 26 3 55 9 31 6 26 8 57 7 29 11 24 4 62 9 32 1 26 0 66 0 33 6 27 0 59 11 30 11 25 1 55 9 30 4 25 3 59 0 30 6 24 10 62 0 31 9 I 25 9 58 2 i 30 2 24 6 65 1 33 1 26 9 55 11 29 2 23 10 62 3 31 11 25 10 55 9 30 1 24 11 58 2 30 2 ! 24 6 55 9 30 11 25 11