August 14, 1914. ____________________________________________________________________________________________________ THE COLLIERY GUARDIAN. than those of almost all other trades, they should receive as much protection as possible from the Government. They refer specially to transport rates. Without objecting to the consumers trying to keep the high price of coal down as much as possible by means of cheaper transport, they com- plain that the concessions made by the railway companies have only been upon coal imported from abroad. They wish the generalisation of special rates upon coal to include the French mines as well as the foreign. In the case of the Centre and Loire districts, which during a period of shortage some months ago chiefly caused, according to the Northern collieries, by a shortage of barges and consequent higher freight rates, special low railway rates were made from the German frontier. This concession expires shortly, and pressure is to be brought to prevent its extension or to have it applied to all lines. ... ____________ Germany. June Exports and Imports.—The following shows the production and distribution of fuel during the six months ended with June :— Coal. 1,000 tons. Lignite. 1,000 tons. Coke. 1,000 tons. Briquettes. 1,000 tons. Production— 1913 . 93,778 ... 15,944 ... 41,900 .. .. 13,183 1914 . 94,148 ... 15,974 ... 44,351 .. .. 14,515 Imports— 1913 . 5,028 ... 253 ... 3,503 .. 72 1914 . 4,776 ... 295 ... 3,184 .. 79 Exports — 1913 . 16,372 ... 3,431 ... 30 .. . 1,638 1914 .. 18,170 ... 2,630 ... 31 .. 1,622 Consumption— 1913 .... -82,234 . . 12,786 .. .. 45,373 .. ,. 11,617 1914 .... 80,754 . . 13,639 .. ,. 47/04 .. . 12,972 Syndicate Exports during 1913.—The exports of German fuel in 1913 continued in the ascendant, rising from 31T5 million tons to 34’57 million tons as regards coal, from 5’85 to 6’41 million tons as regards coke, and from 2’12 to 2’30 million tons as regards briquettes. The Rhenish- Westphalian Coal Syndicate contributed largely to the increase in coal exports, but sent smaller supplies of coke and briquettes abroad. The Syndicate exports in the last six years have been as under, the total including the equiva- lent of coal used in the manufacture of coke and briquettes : Ypav Coal. Coke. Briquettes. Total. Tons. Tons. Tons. Tons. 1908 ... 9,018,220 ... 2,745,801 . 726,372 ... 13,206,744 1909 ... 10,766,034 ... 2,909,084 ... 802,626 ... 15,234,046 1910 ... 11,925,573 ... 3,493,472 ... 1,210,013 ... 17,517,673 1911 ... 13,087,977 ... 3,677,478 ... 1,578,519 ... 19,254,930 1912 ... 14,004,439 ... 4,519,631 ... 1,685,763 ... 21,349,738 1913 ... 15,602,770 ... 4,401,433 ... 1,642,792 ... 22,757,003 Taking a survey of the whole period, it will be seen that the export trade in briquettes shows the greatest expansion, although the last two years have witnessed some retro- gression. The sphere of influence, so far as coal is con- cerned, is circumscribed, for of the total exported in 1913, 12| million tons were sent to three countries (Holland, 6’54 million tons; Belgium, 3’9 million tons; France, 2’12 million tons). The coke exports go further afield, and more coke than coal is sent to Austria-Hungary, Russia, Sweden, Norway, South America, and Australia; but France took no less than half the exports in 1913 (2’25 million tons). Belgium received 311,000 tons, Austria-Hungary 277,000 tons, Switzerland 253,000 tons, Russia 259,000 tons, Sweden 200,000 tons, Italy 173,000 tons, and South America 126,000 tons. Briquettes found their best market in Belgium (412,000 tons), France (311,000 tons), Holland (274,000 tons), and Italy (119,000 tons). About 30’84 per cent, of the total exports were consigned to Holland, 23’27 per cent, to France, and 20’56 per cent, to Belgium. The three countries mentioned took 74’67 per cent, of the total, as against 77’33 per cent, in 1912. Exports to the United Kingdom in the same years were as under :— Coal. Coke. Briquettes. Tons. Tons. Tons. 1908 ... — 132 — 1909 ... — 3,038 — 1910 ... 14,965 .7 17,917 700 1911 ... 16,455 ... 8,700 — 1912 ... 42,974 ... 28,710 10,301 1913 ... 9,850 ... 6,135 — Netherlands. Proposed Canalisation of the Meuse.—Relative to the pro- posed canalisation of the River Meuse, H.M. Minister at The Hague reports that the new Netherlands Minister for Waterways, M. Lely, proposes that, in addition to the original scheme for a canal between the rivers Meuse and Waal, a canal should be dug between the Meuse and the South Willems Canal at Nederweert. The cost of con- necting the Meuse and the South Willems Canal and widening the latter to take vessels of 2,000 tons is esti- mated at £4,167,000, whereas the cost of canalising the Meuse from Maasbracht to Mook, with a canal connecting the Meuse and the Waal, is estimated to cost about £1,583,000. By connecting the Meuse and the South Willens Canal a short means of communication will be opened up between the Limburg coalfields and the indus- trial part of North Brabant, and coal could be carried to the province of Zeeland more rapidly than vid the canalised Meuse. ______ _____________ Russia. According to the British Consul at Helsingfors, 536,975 metric tons of coal were imported into Finland in 1913, as compared with 487,911 tons in 1912. The coke imports amounted to 48,638 tons, as contrasted with 30,801 tons. The quantities received from the different countries were as follow :— Coal. Coke. ______ From f------A-------t------A--------' Tons. Tons. Tons. Tons. 1912. 1913. 1912. 1913. United Kingdom... 457,385 ... 497,636 ... 10,012 ... 24,342 Russia ........... 278 ... — ... 62 ... — Sweden............ 918 ... 909 ... 176 ... — Germany.......... 5,190 ... 13,874 ... 13,930 . . 20,150 Netherlands ...... 23,727 ... 22,611 ... 5,055 ... 3,755 Belgium .......... 412 ... — ... 1,565 ... — Total.......... 487,911 536,975 30,801 48,638 Finland in 1913 exported 1,818,387 cubic metres of props, of which 1,458,567 were consigned to the United Kingdom, as compared with 1,078,368 cubic metres in 1912. The Inflammability of Firedamp and Other Gases.* By F. LEPRINCE=RINGUET. The limit of inflammability of a gas mixture is usually regarded as the percentage content of inflammable gas above which ignition is propagated in both directions in a tube; but there is also a higher limit beyond which no propagation occurs either vertically or horizontally. In his experiments to ascertain these two limits in gases of different composition, the author employed fire- damp taken from the Lievin testing station, and also from a blower in the Jeanne seam at the Lens collieries. It contains methane accompanied by an excess of nitrogen, frequently also of air, and, in some cases, by a little carbon dioxide, which is eliminated before making the tests. The percentage of methane in each sample was deter- mined by the limit of inflammability in a Lebreton apparatus, consisting of a tube 26 mm. in diameter, drawn out to 14 mm., in which the mixture is agitated along with 6 per cent, of its own volume of water, ignition being effected by the aid of a piece of pumice, soaked in methyl alcohol, placed at the mouth of the tube. The results of these tests, were checked by the eudiometer and by the Le Chatelier grisoumetre (incan- descent platinum wire). To prevent confusion it should be mentioned that sampling gases in a mine or for testing is always effected in presence of saturated water vapour, so that the abso- lute composition of the gas varies with the temperature at the moment of testing, whereas the gas is really defined by the proportion contained in the incondensable part of the mixture, which constitutes its relative content. The eudiometer gives the absolute content. The grisoumetre should also give the absolute percentage, provided a correction be made in the ordinary formula, which does not take into account the fluctuations in the vapour tension during the experiment. Numerous com- parative tests have been made with seven sets of apparatus in the Lievin mines, and have shown that, in order to obtain reliable results, it is necessary to prevent luminous radiation, and to keep the gas at a constant low temperature by a water circulation, which, however, is interrupted during the combustions. Finally, for testing with the Lebreton apparatus, three factors must be taken into consideration : the tempera- ture, the percentage of water vapour, and the solubility of the gases in the water used for agitation. x 02- 0) 10- ■ 09 - 08- ■ 07 = 06- -05 - 04- Y 0 15 K 14- ■ 13 - 12-- -----co1 «• z = o» M X = M 02 The presence of water varies the composition of the gas under examination, reducing the proportion of methane and increasing that of oxygen—an important phenomenon when the upper limit of inflammability is in question. The absolute limit for firedamp in air may be expressed—for slight variations in temperature t, and with as the percentage of water vapour—by n — n0 — at + b in which a = 0-0042 (according to Taffanel’s experiments between 20 degs. and 690degs.), and 5 = 0-05, or nearly so (according to the author’s observations), when varies between 1 and 11 per cent., and t between 0 degs. and 49 degs. The relative limit may be expressed by x 100 n — ™ (1 + c............M5 - e1’ - M.......... These results are explained by the cooling action of the walls. The influence of temperature is decidedly independent of the diameter of the tube. The limit of propagation in an upward direction is lower than that of downward propagation. This has been tested in a tube containing two mixtures, by pro- ducing ignition, from above downwards, in a sufficiently rich mixture, and then inverting the tube rapidly at the desired moment. The results obtained in a 27 mm. tube were :— From above downwards ...... n0 = 5*76 ............... Horizontally ............... 5’56 From below upwards ........ 5’20 The upper limit showed a difference of 0-50 between extremes. The lowering of the limit in upward propa- gation is due to the fact that the burned gases tend to remain in contact with the unconsumed gases, and transmit heat to them more completely than when the conditions are reversed. Inflammability of Mixtures of Methane, Oxygen, and Nitrogen. The curves representing the lower and upper limits of inflammability (n0 and n'o) for different proportions of nitrogen in the mixture have been plotted, and are found to intersect. The upper limit is in all cases the limit of propagation corresponding to the diameter of the 26 mm. tube, because the air mingling with the mixture at the orifice facilitates ignition. The lower limit is fairly constant at first, and is the same in oxygen as in the air. The intersection of the two curves occurs when the composition of the mixture corresponds to CH4 + 2O2, that is to say, proportions which fur- nish complete combustion, with 6-70 per cent, of CH4, 29-3 per cent, of N, and 64 per cent, of air. The upper limit in air is 13-10 per cent of CH4; and in oxygen this limit corresponds to 3CH4 4- 2O2, under which conditions the flame is smoky and a deposit of carbon is obtained. (CH N \ y —--------L x — | have been 02 J plotted, and are now reproduced. It will be noted that beyond x = 3-78, which corresponds to the composition of the air, the upper and lower curves are almost rigorously symmetrical with relation to i/ = 0-5. Inflammability of Mixtures of Methane, Oxygen, and Carbon Dioxide. The experiments with carbon dioxide were carried out at the Lievin station, and were performed over damp mercury and by the aid of a special burette containing only 10 per cent, of water, the volume of carbon dioxide dissolved by shaking being noted each time. CO If z be taken to represent the ratio 2, if will be observed that the curve / (1/, z) is only the curve f (y, x) with the abscisses multiplied by 0-56—except for slight divergences which seem mainly due to experi- mental errors, although the presence of CO2 is, in itself, calculated to modify the conditions of com- bustion. It may therefore be concluded that a mixture contain- ing several incombustible gases behaves very much as though each incombustible element were replaced by one of the others, according to definite proportions. It has also been confirmed that, as a consequence of the foregoing law, the curves f (y, z) obtained for mix- tures of firedamp, carbon dioxide, and air, or nitrogen and oxygen in a constant proportion, are none other than the foregoing curve / (y, z) displaced parallel to itself (the same small divergences excepted). In air the intersection of the curves occurs at 7-90 per cent, of CH4, and 16-5 per cent, of CO2. The author is indebted to M. Taffanel for a series of check experiments carried on over mercury, with spark ignition. The tests mentioned above as having been performed writh water vapour are somewhat difficult, because of the accompanying important variation in temperature, during which change the water gives off the greater part of the gas it has dissolved. This was, however, remedied by either leaving only a very small amount of water in contact, or else by comparing the variations in the lower and upper limits, thus ascer- taining at once the co-efficient of solution and the co-efficient due to the water vapour. The influence of the water vapour on the upper limit can be deduced from the above laws, in the same way