August 30, 1918. THE COLLIERY GUARDIAN. 445 CURRENT SCIENCE Use of the Interferometer in Gas Analysis. Messrs. F. M. Siebert and W. C. Harpster (United States Bureau of Mines Technical Paper No. 185) describe the outcome of some of the investigations made by the Bureau of Mines in connection with work on mine gases and natural gas. For special work in the field of gas analysis some of the older analytical methods have been partly supplanted by those that permit analyses at frequent intervals. The Rayleigh interferometer, as adapted to gas analysis by F. Haber and F. Lowe, of Jena, meets this requirement. The interferometer is suitable for analysing a binary gas mixture. In conducting a test the zero point is established by aspirating air through the drying and soda-lime tubes of the apparatus until the reading is constant; this reading may be used as the zero, or the screw may be set at zero and the “ fixed ” plate moved by gentle taps exactly into position. The gases passed into the chambers must have the same temperature, pressure, and moisture content. A small wash bottle of con- centrated sulphuric acid serves as a drier and also indicates the rate of flow. A phosphorous pentoxide tube may be added to remove the last traces of mois- ture. For obvious reasons the total volume of this system should be as small as possible. The authors found that about 200 or 300 c.c must be passed through before the reading became constant. The opposite ends of the chambers are fitted with capillary tubes to prevent diffusion and ensure equality of pressure. Since all parts are mounted on a single optical axis, careful lateral adjustment is necessary. If the adjust- ment is disturbed its correction is a matter of consider- able difficulty. The lens in front of the Nernst lamp should be so adjusted that the slit in the collimator is in its focus. Different intensities of the two black bands in the centre of the field indicate faulty adjust- ment of the light. The average observer makes adjust- ments to about one-twentieth of the width of the black bands. The interferometer may be used to investigate mine gases. The outgoing air currents from mines contain carbon dioxide and'methane mixed with air. It is found that a decrease in the amount of oxygen and a corresponding increase in the amount of nitrogen are indicated by the instrument as an increase in the methane and carbon dioxide content. Hence, regard- less of the cause of contamination of the air, by the addition of methane or carbon dioxide, or the with- drawal of oxygen, the instrument indicates imperfect ventilation. Another use of the interferometer is in determining the degree of carburisation of illuminating gas car- bur etted with benzole. The instrument should be calibrated to read in grams per cubic metre or volume per cubic foot, instead of in volumetric percentage. This may be done by passing atmospheric air through the standard chamber and by passing through the other chamber air in which a determined volume of benzole has been allowed to vaporise. A sensibility of 0T gram per cubic metre is to be expected. A further application is the determination of ammonia in distillation gases. Available data show that in this determination the instrument may be made to show a sensibility of 0.3 gram per cubic metre. A common task in gas analysis is the determination of the composition of smoke and flue gases for the purpose of boiler control. One of the chemists of the Bureau of Mines is applying the interferometer to this pro- blem. The interferometer may also be used to deter- mine the efficiency of a given system of ventilation; in the control of mixtures of natural gas and air used in galleries for testing the safety of explosives; and in ascertaining the character of mixtures of sulphur dioxide and carbon dioxide resulting from organic oxidations. Cottrell Process for Cleaning Blast Furnace Gas. According to Mr. H. D. Egbert (Blast Furnace and Steel Plant), interest in the Cottrell process of cleaning blast furnace gas has been stimulated by the fact that the dust often contains compounds of zinc, lead, man- ganese and potash, which are easily recoverable by the use of a dry, hot-cleaning process in preference to a cold, wet method. The principle of the Cottrell process is that if a body highly charged with electricity is brought near to a particle able to move freely in any direction, the latter will receive a charge of the same sign as that of the charged body, and will be violently repelled from it. This is what takes place in an elec- trical precipitator, except that the charged body is fixed and the particles are brought to it. In its simplest form the precipitator consists of two sets of electrodes. One, known as discharge electrodes, are of such a form as to facilitate an electric discharge from their surface, as, for instance, a wire or light chain. The other set, known as collecting electrodes, are of such shape as to prevent as far as possible any discharge from their surface, as, for instance, a flat plate or pipe. The different types oppose each other, and between them a silent or glow discharge is maintained by impressing on the discharge electrode a uni-directional current of high potential. The gases carrying the suspended particles to be removed are passed between the discharge and collecting electrodes; the particles become charged and are driven away from the discharge electrodes and across to the collecting ones, upon which they are deposited. The .gases are unaffected and( pass on out of the precipitator chamber. Effective precipitating action is not obtained unless the potential difference between the electrodes is suffi- cient to produce a corona, and with high potentials, wires, rods, chains and metal strips are successfully used as discharge electrodes. If the collected material is dry, it is often necessary to dislodge it from the collectors by mechanical means. This is usually accom- plished by striking the pipes or plates, whereupon the material falls into hoppers placed to receive it. Sometimes it is also necessary to clean the discharge electrodes. A precipitator to deal with 10,000 cu. ft. AND TECHNOLOGY. per minute usually requires from 7 to 10 kilowatts. The power consumption is, however, governed by the number of electrodes, their length and size, as well as by the characteristics of the gases as regards tem- perature and conductivity. A typical set of electric equipment and a precipitation plant are illustrated. The method is being also adopted in connection with sintering installations, the gases from which contain free sulphuric acid, and sometimes elemental sulphur. Dry Producer Gas from Coke. Mr. M. Brautigam (Stahl und Eisen) describes a producer working on coke and yielding gas containing not over 12 grammes of moisture per cubic metre. The producer is fired with coke, and mixer or basic slag or other kinds of slag rich in iron are used to flux the coke ash. The resulting fused slag is drawn off through a tap-hole at the bottom of the producer, and with it iron high in manganese and phosphorus is obtained. Air warmed to about 70 degs. Cent, is blown in through six nozzles spaced circumferentially at the bottom of the hearth, like the tuyeres of a blast furnace, and in form the whole apparatus re- sembles a miniature blast furnace. The charging is done through hoppers at the top in the usual way. By-Product Gas Producers. Mr. G. Klingenberg (Stahl und Eisen) discusses the economy of by-product recovery in connection with the working of power gas installations, and summarises generally the results of tests and experiments carried out by previous investigators with peat, brown coal, Westphalian anthracite, Silesian coal and waste coal. A table of results of tests on Mond gas installations using the above fuels is given. The gas from brown coal has the highest calorific value, with 1,445 calories per cubic metre, of any of the gases from other fuels, notwithstanding that the raw brown coal, with 2,720 calories per kilogramme, has a lower calorific value than any of them. THE WATERLOGGED COAL AREA IN SOUTH STAFFORDSHIRE. The following note is taken from the Final Report of the Mining Sub-Committee: — The coal mining district most seriously effected by waterlogging is that of South Staffordshire and East Worcestershire known as “the Black Country.” In the early days of mining operations in this area the coal was chiefly got from the outcrops of the "thick coal” or from shallow mines, with little atten- tion to system or method, the surface becoming lowered and broken and forming a great gathering ground for surface water to percolate into the mines, and a large part of the area now more resembles a rabbit- warren on a grand scale than a systematically mined field—a warren filled with water. The condition of affairs became so bad that in 1873 the South Stafford- shire Mines Drainage Commission was constituted under a local Act, amended by several later Acts, to perform in the parts of the South Staffordshire and East Worcestershire, known as the South Staffordshire Coal Fields, the work of— Draining of surface water; Pumping out mines and keeping them drained. The tunnels for drainage are treated as mines, with some doubt, but the concern of the Mines Department of the Home Office ceases with questions arising out of the method of excavating, etc. The question of the economy of the dispositions made is entirely one for the Commission itself and for the electors, who elect and may also take part in constituting it. The Commissioners number 30, and are elected by the owners and occupiers of mines with certain ex officio members representing public bodies (Section 6 of the Act of 1873). There is no reference to any Govern- ment Department except that one of the later Acts concerned with finance provides that a referee to determine certain disputes shall, if necessary, be appointed by the Board of Trade (Section 13 of the Act of 1894). Various estimates have been made from time to time as to the extent of the coal under water. Mr. Isaac Meachem, who has had a most extensive knowledge of the matter, has stated that “he does not think that he is greatly mistaken in saying that there are now upwards of 40,000,000 tons of coal and ironstone in the earth which will be utterly lost unless some scheme is devised and set to work to rescue them.” ‘ ‘ The loss of this mineral wealth is a serious matter, and what it means to the district cannot be adequately realised. Not only so, but ominous signs may be seen that the output of minerals in this district will in the near future be so reduced that the income there- from in the way of mine drainage rates will be in- sufficient to pay the working expenses of the necessary machinery with which to keep the Commission going.”* Some local mining engineers consider that Mr. Meachem’s estimate is unduly pessimistic; that the loss would be distributed in small isolated patches, and that it could hardly be held that the coal, etc., would be irretrievably lost. Others regard his estimate as conservative, and 50,000,000 and even 70,000,000 tons has been given as the amount of mineral wealth—coal, ironstone and fireclay—involved. In respect ot surface drainage, the Commissioners have expended large sums of money in the purchase and removal of water mills, thus reducing the level of the water in the main streams, also in deepening, straightening, embanking, and clearing streams so as to have a uniform gradient and sufficient sectional area and water-tight channels to convey water from the higher grounds where the streams take their rise, through the broken and sunken ground, where mining * “ Notes on the loss of Mineral Areas in South Stafford- shire,” a paper read by Mr. Isaac Meachem before the Institution of Mining Engineers, February 19, 1912. has most affected them, to the outfalls at boundaries of the districts drained by the rivers Terne and Stour, one on the north-east side of the area and the other on the south-west side. The main streams are kept clear of mud and silt, and nearly all the smaller branches have also been cleared up to their rise in the higher ground of the central district. The net result of their operations, according to witnesses who appeared before the Committee, is that less than half the former quantity of water now passes into the mines. For the purposes of the “ pumping out mines and keeping them drained,” the area is divided into five districts, and one of them again is sub-divided. The districts are— 1. Bilston Area. Square miles. 4*47 or Acres. 2,861 2. Tipton 33'35 „ 21,344 3. Oldbury 13 88 „ 8,883 4. Kings winford 12'32 „ 7,885 5. ma ttui (Northern Sub-district Vid Hill £ Southern Sub-district Total area } 16-77 „ 80'79 „ 10,733 51,706 The Commissioners have carried out mine drainage work in the Tipton and the Old Hill (Northern Sub- District) districts. In the Oldbury, King’s Winford and Old Hill (Southern Sub-District) districts no mines drainage work has been done by the Commis- sioners. There are large quantities of coal, ironstone and fireclay in these districts. The Bilston district contains limestone only, and nothing is being worked. The Tipton a^ea is that in which the greatest quan- tity of water occurs. It is the most difficult to deal with, and may be regarded as the crux of the whole drainage problem in South Staffordshire. In this area the Commission control 300 miles of streams and nine central pumping stations. There are 80 rated col- lieries, with an output of 420,000 tons per annum, and the proportion of water pumped to coal raised is as 50 to 1. Included in the area there are 26 local authorities. Unless some financial arrangement is come to whereby the Commission will be kept going, the pumping stations in this area will in the year 1924 pass to the Birmingham Canal Company in accordance with an agreement made in 1914 and confirmed by Parliament, but some water, at any rate, will have to continue to be pumped from the mines in order to supply the canals. At June 30, 1882, the indebtedness of the Tipton district was £120,855; at June 30, 1917, it was £655,820, showing that £534,965 had been expended in 35 years above and beyond the revenue from rates and other income. In this period the tonnage assessed for mines drainage rate was 21,997,759, the indebted- ness beyond the revenue being therefore 5-83d. per ton. The Drainage Commissioners have, we believe, spent over £750,000, £600,000 of which was raised by the issue of bonds on which no interest has been paid for about 20 years or more; in addition to this they have exhausted their borrowing powers. Their annual in- come is said to average about £30,000, of which some £18,000 is required to pay interest on the borrowed money, leaving about £12,000 for working schemes, which is a sum insufficient to permit of their doing more than keep the water at its present level. To put the Commission on a sound financial basis it would re- quire to possess an annual income of £40,000 (which at a Is. rate means an output from the Tipton area of 800,000 tons per annum, whereas the output at present is but about 400,000 tons), and, in addi- tion, a sum of £20,000 to liquidate outstanding liabilities. In the early years of the Commission’s existence they drove a series of water, levels to convey the water from the surrounding mines to their pump- ing stations. At present they are only able to keep their levels in repair, and have no funds with which to drive similar levels; consequently some isolated mines are compelled to “tank” their own water, as it cannot reach the Commissioners’ pumps unless allowed to rise to a height sufficient to give it the requisite head. The position in respect of water level in the drainage area is affected by the state of the weather; in exceptionally dry seasons the Commis- sioners are able to lower the level, and consequently extend the area of coal which can be worked. Thus, in the summer of the year 1911, which was an excep- tionally dry one, the Deepfields pump lowered the water about 65 yards (vertical). The funds of the Commissioners are obtained from graduated tonnage rates imposed on collieries in the area drained by the Commissioners, the Commission having power to assess on coal, ironstone and fire- clay. The maximum rate imposed is 9d. per ton for underground drainage plus Id. per ton for surface drainage. The average rate in the Tipton area is 6-34d. The assessment is varied in accordance with the benefit received. The position of the South Stafford- shire coal field has been, in respect of the present drainage system, aptly likened to a tank full of water in which are placed a number of buckets of the same depth, each of which represents a separate colliery area, with the Drainage Commission pumps drawing the water from the spaces between the buckets. As has been stated, the financial position of the Com- mission is precarious, owing to the rated output of coal from the field being insufficient to allow of the extension of drainage operations; but, although the drainage work is under present circumstances too limited, were these operations to cease altogether, disaster would overtake a number of small under- takings. The position is one which should be enquired into in detail by an expert committee set up by Government for this purpose. Partnership Dissolved.—The London Gazette announces dissolution of the partnership of E. W. H. Wilkinson (who continues the business) and F. G. N. Wilks, trading as Farwig and Bullock, tinplate manufacturers, 16, Rupert-street, London, W.