May 24, 1918. THE COLLIERY GUARDIAN 1051 each level, part of the air is taken out and direct connection is made to the flexible tubing that runs to the breast of the crosscut. These headings have advanced about 300 ft. on each level. In spite of the high rock temperatures, the working conditions at the breast have been kept very comfortable. By having at each working place a number of short lengths, the men can bring the lead piece as close to them as they wish. When the short lengths are all in use, a long length is sent down to take their place. This order of changes is repeated time and again as the work progresses. In these levels, 10 and 12 in. tubing is used, and no tension rings are required in connection with the clamp that grips the wire, but the clips that are bent around the wire messenger to support the tubing must be carefully tightened. Tubing in Raises and Stopes. Considerably more care must be exercised in the use of the canvas tubing for ventilating raises than peed be taken in crosscuts or drifts. Where the rock temperature is high, it will be found that added advance and the consequently diminished cost will repay amply the time spent in placing and protect- ing the tubing. In all the vertical portions of the raises, the tubing must be boxed for protection from falling rocks. The boxes need not be air-tight, and can quickly be thrown together out of 1 in. material. At the offsets the tubing need not be covered. The discharge from the top box must be covered with a screen to keep falling pieces from going down the tubing, and it must be specially well protected when blasting. In one stope with ample connection between levels, a No. 4 fan and 16 in. tubing completely reversed the air currents, with a resulting drop of 15 degs. This good result was accomplished without causing any apparent ill effect in the other workings. Direct-Current Mounted Fans. Often places are met, in both stoping and develop- ment, where artificial ventilation is needed only for a short time, while a raise is being put through, or a crosscut or drift is being extended. Such work may take a month or less, and conditions may be such that it is impossible to hold men in these places. The short period of time that is needed to have a fan blowing, before natural ventilation can be attained makes a concrete foundation superfluous, and wood foundations are undesirable on account of fire risk. As motor haulage with direct current is used almost entirely in this mine, and as the trolley lines reach almost every part of the mine, some No. 2 and No. 3 direct-current fans have been mounted on trucks with heavy plates arranged so that they may be turned to any angle (in a horizontal plane) with the trucks. One, complete with its auto-starter and the canvas tubing, is run to the place where needed; here it is thrown (truck and all) from the track, or placed on a siding; a wire messenger is strung, connections are made for electric current, and the fan started with comparatively little work. These fans are moved from place to place, and will in a short time save in labour and foundation material the cost of the truck and time of mounting. Within the last few months, many improvements have been made on the tubing. The first supplied was coated on one side only, had no means of support, and an inconvenient and inefficient means of connect- ing lengths. As shipped to-day, the tubing is coated on both sides, has a wide top hem in which, at intervals of a few feet, are grommets and suspension clips, and at the ends of each section are coupling rings, which make its installation very simple, rapid, and satisfactory. The author’s experience with canvas tubing has now extended over a period of more than a year. It has been tried in all kinds of working places, and has amply repaid the cost of installation, being in every way more satisfactory than metal tubing. PARLIAMENTARY INTELLIGENCE. HOUSE OF COMMONS.—May 16. By-Products. Captain Barnett asked whether the product now ob- tained from the distillation of cannel coal at gasworks was of any value as Admiralty fuel; and whether the offer by the Controller of the Munitions Mineral Oil Depart- ment of a £2,000 prize to any person who could make a satisfactory mixture of dehydrated coal tar and pertoleum indicated that low temperature distillation would be better adapted for the production of liquid fuel from cannel coal. Mr. J. Hope said it was expected that the product now being obtained from the distillation of cannel coal at gas works would be of considerable value as an Admiralty fuel. The prize offered by the Controller of Munitions Mineral Oil Production Department was for a different purpose altogether, having as its object the utilisation as fuel (in addition to cannel oil) of large quantities of tar at present available from gas works not using cannel. Coal Difficulties in Glasgow.—The difficulties expe- rienced by the retail coal trade in Glasgow in consequence of the shortage of supplies were discussed at a meeting of representatives of the trade convened by the Bridge- ton Coal Dealers’ Association last week. In the course of the meeting it was stated that if the conditions which had obtained during the past six weeks continued much longer many traders probably would be obliged to give up business, as under existing circumstances an adequate return was not received for the expenditure involved in the upkeep of horses and the cost of labour. On the suggestion of the South-Side branch it was agreed that a system of “ idle ” days should be introduced, the idea being that during these days merchants may accumulate sufficient stocks to ensure a full day’s employment for the retailer on working days. A number of members of the trade, it was stated, could find other employment for their horses and men on the days they were not engaged in delivering coal. The meeting decided to inform the Coal Controller of the proposal. CURRENT SCIENCE New Universal Travelling Grate. In the Pluto stoker (described in the Elektrotech- nische Rundschau) special provisions are made against air leakage, and it is claimed that any solid fuel can be burned to best advantage. A special type of grate bar is used, which prevents appreciable loss of fuel through the grate, and secures efficient combustion. The grate bars are about 100 mm. wide and 200 mm. high. They are in the form of U-shaped pipes with a stepped upper surface. There is a slot in the vertical portion of each “step.” Air to support combustion enters at each end of the hollow grate bars, and is thus pre-heated whilst effectually cooling the grate. Steam may also be used with caking coals. Artificial draught may be applied. The fuel falls automatically into the inclined step grate, horizontal and vertical control plates regulating the feed and controlling the depth of the fire bed. Reciprocation of the individual fire bars advances the fire as combustion proceeds. The ash plate at the back of the grate is arranged so as to protect the lower part of the bars and prevent ingress of surplus air. When burning very gassy coal, an auxiliary air supply is admitted at the front of the grate and uniformly over its whole width. Test data are given, showing the efficient combustion of low-grade brown coal with 30 per cent, moisture and 25 per cent. ash. All work- ing parts, except the grate bars themselves, are out- side the fire box. According to the grate area, from J to 1 h.p. is needed to drive the stoker, but should the power fail operation can be continued as an ordi- nary inclined grate, oscillated at intervals by hand. Purifying Water for Steam Condensers. A communication (Elektrotechnik und Maschinen- bau) to the Union of Electricity Works in Germany concerning the effects of impure circulating water in surface condensers and methods of purifying water for this purpose, states that the condenser vacuum is reduced by the combined effect of obstruction to heat flow and throttling of water circulation caused by scale deposits in the tubes. It is better to use purified water than to interrupt normal working to clean out the tubes. In the Martin “ clarifier,” water enters at the funnel-shaped bottom of a vertical drum. The velocity of the water decreases as it rises through the funnel; hence most of the mechanical impurities settle out. Once it is started, the apparatus is auto- matic in action, clear water being syphoned away from the top and sludge draining out at the bottom. A clarifier dealing with 15,000 gals, per hr. has a settling drum 16| ft. diam. and occupies about 300 *sq. ft. ground surface. A special outlet is provided at the top for grease, oil and gas. The equipment is more convenient than settling ponds, and gives over 80 per cent. “ purification efficiency.” Chemical purification may be needed in addition. A Martin clarifier is used in Waldenburg electricity works, together with a Reisert water purifier, which comprises a cylindrical reaction tank, a distributor, two conical saturators, and a gravel filter bed. The apparatus is in the open, and can be worked even when the air temperature is —25 degs. Cent. In these works the total cost of purifying circulating water is about 1'61 pf. per cub. m. or 0’03 pf. per kw. hr. generated. The condensers need cleaning only twice a year instead of once a fortnight, and the annual cost of cleaning is about one twenty-fifth of what it was before purified water was used. There is con- siderable loss of water by evaporation from cooling towers, on the laths or brushwood of which serious deposits are formed if the water be impure. The Dissociation of Salt. In a paper read before the Refractory Materials section of the Ceramic Society, Mr. H. V. Thompson describes the results obtained in a series of experi- ments made to determine the hydrolysis of salt in the neighbourhood of 1,100 degs. Cent. Selected chips of quartz from the Isle of Man were exposed to the action of salt and water vapour for periods varying up to six hours, at approximately 1,100 degs. Cent. In all cases the quartz had more or less lost its glassy appearance, being of an opaque white colour, while the sharp edges and rough faces had become smooth, but the reactions were only super- ficial. Experiments were then made to determine, if possible, the composition of the glaze on the quartz, the quartz chips being well washed with hot water and the washings tested gravimetrically for silica. No water-soluble silicate could be detected. The washed quartz was then digested with 35 c.c. of water and 10 c.c. of concentrated hydrochloric acid, and gave a mean value of 1’000 Na2O to 1’023 SiO2, which may be taken as representing equi-molecular proportions. The mechanism of the reaction is probably that the current of air carries forward the salt vapour, which impinges on the quartz and adheres to it, covering the surface with a thin film of molten salt, and at the same time the salt is hydrolysed by the water vapour with the formation of a sodium silicate insoluble in water. The insolubility of the silicate in water is apparently due to the high temperature to which it has been exposed. The insolubility is analogous to the insolubility of strongly ignited alumina or iron oxide in hydrochloric acid. Two experiments were made in which quartz at a temperature of 1,165 degs. Cent, was exposed to salt vapour and dry air for 13J and 14| hours respectively. In spite of the prolonged heat treatment the quartz was markedly less attacked than when it had had a much shorter period of heating in a current of moist air. Alumina, when heated with salt for twelve hours before a Teclu burner became coated with a layer of fused salt. The fused mass of salt and unchanged alumina was then digested with water. Two experi- ments gave 1 A12O3 to 4’19 and 4’76 Na20 respectively, which may or may not indicate the formation of a sodium aluminate of the empirical composition 2Al2O3,9Na2O. AND TECHNOLOGY. In all the experiments the action was only very slight and apparently quite superficial. However, under industrial conditions, the constituents of a clay or brick are exposed continuously for months, or even years, to the combined action of salt and water vapour, and it is not to be expected that a similar amount of attack will be apparent in laboratory experiments of a few hours’ duration. Also the combined action of salt and water vapour on a highly complex body, such as a clay, is not strictly comparable to their action on the separate constituents of a clay. Toluol from Sulphite Wood Pulp. The special committee on toluol of the Technical Association of the Paper and Pulp Industry recom- mends the adoption of the following method developed by the Hammermill Paper Company: — Separating the relief gases and liquor, sending the relief gases through the gas cooler to a second separator, this separator taking out the cymene plus a certain quantity of other condensates. The dimen- sions of this separator for both the intake and dis- charge are about 6 in. in diameter, and the separator itself about 15 in. in diameter and 5 ft. deep. There is a lead baffle plate placed in the middle of the separator reaching to within a foot of the bottom. In the bottom of the separator is an outlet of about 2 in. diameter, which conducts to a separating tank the cymene, together with an aqueous SO2 solution. This tank should be equipped with gauge glass and indicator cocks. The gauge glass hitherto used is subject to freezing, and it would be more advisable to have a stave mortised and a section of from | in. to | in. plate glass inserted from 2 in. to 3 in. wide and 4 ft. long, answering as a window to the tank itself. From here the aqueous solution of SO2 is drawn from the bottom of the tank back to the acid storage tanks, and the cymene, to tanks for the purpose of collecting the same. The more frequently this opera- tion is repeated, the better the resulting production will be. Toluol from Spruce Turpentine. Mr. A. S. Wheeler (Journal of Industrial and Engineering Chemistry) has experimented with the production of toluol from spruce turpentine, which consists largely of one aromatic hydrocarbon, cymol. The spruce turpentine was purified by first subject- ing it to distillation in superheated steam, the vapour being carried through hot 10 per cent, caustic soda and then condensed in the usual way. The crude turpen- tine was pale red, but the condensed oil was brilliant and water-white. The caustic soda assumed a reddish colour. Seventy per cent, of the oil passed over into the receiver, but a newer shipment is giving a larger yield as high as 87 per cent. If caustic soda is not used the distillate is lemon-yellow in colour. The oil was separated from the water and shaken several times with 0’5 per cent, potassium permanganate, then 20 times with one-sixth its volume of concentrated sul- phuric acid. The first addition of sulphuric acid assumed a very dark colour, later washings a red colour, and finally a pale yellow colour. The oil was then shaken with water several * times, dried with calcium chloride, and finally boiled with metallic sodium. It was distilled with a Glinsky still head and the main portion, boiling at 177-177’5 degs., was employed in the reaction. The aluminium chloride was freshly prepared by passing dry hydrochloric acid gas over hot aluminium filings. The proportions taken were 90 pts. cymol, 900 pts. benzol, and 4’5 pts. alu- minium chloride, boiled together on a water bath for 10 hrs. The fractionations of the product were carried out with a three-section Young still head, toluol and cumol being obtained. The latter is not a waste product, since it may be oxidised directly to benzoic acid. This will save a like amount of toluol now used to make benzoic acid. OBITUARY. The death took place on Wednesday last week of Mr. Richard Laithwaite, chief engineer of the Wigan Coal and Iron Company Limited. The deceased gentleman, who was 57 years old, was a native of the Wigan district, and had been with the Wigan Coal and Iron Company Limited throughout his career. Mr. Hugh McStay, coal agent at Dunston Staiths, Gateshead, died suddenly on Sunday last at his residence. Mr. McStay took an active part in local affairs. U.S. Mining Fatalities.—Official reports have been issued relative to fatalities in the coal mines of the United States in 1917. The abnormal conditions are reflected in the accident records by an increase of 21 per cent, in fatali- ties as compared with 1916. The reports of the coal mine inspectors to the Bureau of Mines during 1917 account for 2,686 fatalities at the coal mines of the United States, as compared with 2,226 for 1916. It is not possible to give the number of men employed in 1917, but preliminary reports to the United States Geological Survey indicate that in some States there was a slight increase in the number of men employed, whereas in others there was a small decrease. Strike Trouble in South Wales.—The position of affairs in regard to the strike of about 8,000 men at the Tredegar Company’s collieries has formed the subject of’ keen dis- cussion. The whole of the pits stopped work because of the dispute affecting twenty men at one of the collieries, and in doing so they broke the agreement which the Federation had made with the coalowners that stoppage of work shall not take place until questions in dispute have come before the Disputes Committee of the Con- cilation Board. Mr. A. S. Tallis, managing director of the Tredegar properties, has issued a letter showing that his attitude in refusing to meet the combine committee is in accordance with the arrangement that disputes should go to the joint standing Disputes Committee of the Concilia- tion Board, as had been arranged with the Federation officials. The Coal Controller refused to receive a depu- tation until the men resumed work, but the miners, by an overwhelming majority, decided against resuming in that way.