852 THE COLLIERY GUARDIAN. May 5, 1916. ■ CURRENT SCIENCE Fusion Temperature of Ash. Some information on the above subject is given in the Black Diamond by W. I. Stuckenberg and J. F. Kohout. It is not unusual now in America to find a “ minimum ash fusing temperature ” specified in coal contracts. The authors have attacked the subject from a new direc- tion. Three samples of coal, one each from three different mines, were used. The ash and sulphur were determined in the raw coal, and the fusing temperature of ash was observed. The coal was then washed, and similar determinations were made on the washed coal. As was to be expected, the ash and sulphur content of the washed coal was materially less than that of the corresponding raw coal. The surprising feature was that the fusion temperature of the ash was practically unchanged. If anything, the ash of the washed coal softened at a slightly lower temperature than the ash of the raw coal. The ash and sulphur were determined according to the standard methods, and the ash was formed into cones, or, more exactly, triangular pyramids about 2 in. high and -J in. at base. Three cones of the same ash were placed in the furnace at the same time, and were heated side by side. As soon as the cones showed a perceptible bending motion, the temperature was recorded, and one of the cones was taken out of the furnace. The heat was increased gradually, and when one of the remaining cones had inclined to about a hori- zontal position, the temperature was taken, and the cone withdrawn. The third cone was heated until it had fused to a shapeless molten mass. The following tabulation shows the results obtained. The three samples of raw coal were lettered respectively A, B, and C, the corresponding washed coals Al, Bl, and Cl, and the refuse A2, B2, and C2. All tempera- tures are expressed in degrees Fahrenheit. Raw coal A. Washed coal Al. Refuse A2. i Raw coal B. Washed coal Bl. R -fuse B2. Raw coal C. Washed coal Cl. Refuse C2. Dry ash, per cent 9’11 4’51 66’83 14’82 8’08 65’27 10’13 6’24 67'82 Sulphur, per cent Fusion temperature : — 0’73 0*47 — 0’75 0’49 — 0’67 0’37 — Pone No. 1 2,300 2,255 — 2,336 2,318 — 2,318 2,300 — Cone No. 2 2,300 2,363 — 2,354 2,318 — 2,354 2,300 — Cone No. 3 2,444 2,552 — { 2,390 2,390 -— 2,408 2,408 — That there was a considerable difference in composi- tion between the raw and washed coal of each sample, is clearly indicated by the change in the ash and sulphur content. However, the temperature at which the ash from the raw and washed coal from each sample fused is very nearly the same, as mentioned above. ' This seems to show that the fusion temperature depends rather upon the fusibility of the intrinsic portion of the ash (non-combustible material in the coal matter itself) than to that of the extraneous ash (non-combustible material from floor or roof of mine and from bands or partings in the seam). The amount of ash in the coal also seems to have no effect on the fusion temperature. Of course, the above statements apply only in those cases where the coal is burned unmixed with such impurities as sweepings and like refuse, such as is usually found in dwellings. In such instances, where all refuse and garbage is incinerated in the furnace, clinkering may occur even with a coal whose ash shows a high fusion temperature. If clinkering occurs under such conditions, the fault should be charged to the coal only with caution. A New Turbine. The Brush-Ljungstrom steam turbine was described at a recent joint meeting of the North Staffordshire branch of the Colliery Managers’ Association and the Lancashire, Cheshire, and North Staffordshire branch of the Association of Mining Electrical Engineers. Mr. Lloyd-Evans explained that the turbine was composed of two parallel discs, carrying alternate members of a series of concentric blade rings. Steam was admitted at the centre, and flowed through each ring in turn as it passed to the outside, the two sets of blading revolving in opposite directions. The mechanical advantages might be summarised thus : The weight was reduced to a minimum; the plant occupied a minimum of space; it was independent of high temperatures or superheats ; only small leakages took place between the stationary and moving parts; corrosive effects on the exhaust blading were reduced to a minimum; and the complete set was self-contained and independent of foundations. So far, it had only been used for electrical purposes. The Properties of Natural Gas. In a technical paper (109), issued by the United States Bureau of Mines, on the “ Composition of the Natural Gas Used in Twenty-five Cities,” G. A. Burrell and G. G. Oberfell add a discussion of the properties of natural gas. The Bureau of Mines has determined the explosive limits of mixtures of air and the natural gas used in Pittsburg, this gas being typical of that supplied to many cities. The limits were determined in a Hempel explo- sion pipette over mercury. Ignition was brought about from above by means of a small electric spark from an induction coil, driven by four dry cells. The smallest quantity of natural gas in a mixture of natural gas and air that upon ignition completely inflamed as observed by the eye was 4-92 per cent. The largest proportion was 11-50 per cent. . In its determinations of explosive limits of methane-air mixtures, the Bureau of Mines has found that large containers (130 litres capacity) and ignition from below with a large electric flash give wider limits than a small vessel and ignition from the top. In the case of methane-air mixtures, the difference on the AND TECHNOLOGY. low limit was 0-5 per cent. This is probably true of natural gas-air mixtures; in other words, instead of 4-92 per cent, natural gas being the low limit, under other conditions the limit may be as low as 4-50 per cent. The upper limit is undoubtedly extended as much. For complete combustion, 1 cu. ft. of pure methane requires 9-5 cu. ft. of air; 1 cu. ft. of the natural gas used in Pittsburg requires 10 cu. ft. of air. No carbon monoxide, hydrogen, and olefine hydro- carbons were found in any of the samples of natural gas examined, although all of them were carefully tested for these constituents. The authors believe that these constituents are not present in natural gas, although many published analyses contain them. The Bureau determined by experiment that the mix- ture of air and the natural gas of Pittsburg, containing the maximum proportion of natural gas that will burn with complete combustion of the air and gas is 8-6 per cent. The principal inert dilutant of natural gas is nitrogen, the proportion of which varies from 1 per cent, or less to 30 or 40 per cent, in gases used commercially, and, in exceptional cases, much higher. A sample of marsh gas obtained from the • State of Washington contained, according to analyses made by the authors, as much as 98-5 per cent, of nitrogen. The presence of rare gases in natural gas is at present principally of academic interest, as they are inert like nitrogen. That they are present, however, in small proportions has been shown by several investigators. Helium especially has been the subject of considerable research, as it is regarded as the final product of all radio-active decomposition pro- cesses. Numerous investigations begun about 10 years ago showed that the majority of gas outbursts from the earth carry with them a radio-active emanation, which they have absorbed while passing through the earth strata within which the radio-active process of decompo- sition takes place. In many cases the emanation proved to be radium. Numerous minerals, rocks, soils, under- ground air, and atmospheric air, as well as water and gases from springs, have been examined for their radio- activity, often in connection with their helium content. Natural gas contains no carbon monoxide or other poisonous gases, except hydrogen sulphide in occasional samples. But, to the authors’ knowledge, natural gas containing hydrogen sulphide is not used in any city. However, there are present in the natural gas used in many cities small proportions of the higher paraffin hydrocarbons, butane and pentane. The proportion of natural gas in air required to produce collapse in canaries is very large (65 per cent, or more). With as much as 63 per cent., collapse did not occur in one hour’s time, although the distress was immediate. The results of the experiments indicate that, as far as the action of natural gas ■ on canaries is concerned, it is largely a question of a deficiency of oxygen produced by diluting the air with natural gas. As far as the diluting action of nitrogen and natural gas in lowering the oxygen content of air is concerned, the two are nearly similar in the effects produced on canaries. Possibly the same is true as regards man, but to make certain of this point, experiments would have to be made on human subjects. One is safe, however, in drawing the conclusion that a large proportion of natural gas in mixture with air is required to affect man, and that the danger of death to the occupants of a room because of natural gas escaping from an open gas jet is remote, because of the very large quantity of gas required. No account is taken in the foregoing of the imperfect combustion of gas, either natural or artificial, in poorly constructed gas stoves. The danger in such cases from either gas is great, and not only should stoves be well constructed, so that perfect combustion takes place, but every stove should be equipped with a vent leading to the house chimney to take away the products of combustion. Out of the samples of natural gas from 25 cities in the United States, five contain methane only as the combustible gas. The others contain, in addition to methane, higher members of the series of paraffin hydrocarbons. Some of tlie natural gas used in Texas has a heating value of about 740 British thermal units per cu. ft. at 0 deg. Cent, and 760 mm. pressure. The highest heating value determined was 1,312 British thermal units per cu. ft. Lime as a Preventive of Ankylostomiasis. In Italy, the only mineral industry in which ankylo- stomiasis is prevalent is sulphur mining, in Sicily and the Romagna, where it has been known since the early eighties, and has occasionally attained the proportions of an epidemic. In consequence of the observations made by Dr. Manouvriez in mines where tlie water was highly saline (NaCl), it was decided to try lime and salt, the former in the Busca mine, and the latter at For- mignano. The experiments lasted two years, and were completely successful, the number of infected workers being reduced from 38 per cent, in 1908 to 5-2 per cent, in 1910. Owing, however, to the inconveniences arising from the use of salt, lime alone has since been employed as local disinfectant, and this treatment has resulted in the infection declining from 3-3 per cent, in 1911 to 0-25 per cent, in 1914, so that the disease may be regarded as finally got under. Operations are now to be extended to the sulphur mines of Sicily, under the auspices of the Ministries of the Interior and of Agriculture, in conjunc- tion with the sanitation corps of the Mutual Assurance Syndicate.—Mctallurgica e Chimica. THE GERMAN COAL AND IRON TRADES. We give below further extracts from German periodicals that have reached us, showing the course of the coal and iron trades in Germany :— Maximum Fuel Prices in Germany. The recent decision of the Federal Council to extend the miximum price regulations to coal, brown coal, coke and briquettes is attributed to the growing tendency on the part of producers to advance prices out of all pro- portion to the increased cost of production; and since the period of making new contracts was approaching, the Government wished to limit prices while there was still time for the measure to bo effective. The Cologne Gazette, however, points out that such a counse was unnecessary in the Ruhr district, because the State mines administration has the right under the new Syndicate agreement, to oppose undue advances in price, and also to retire from the Syndicate by giving