908 THE COLLIERY GUARDIAN. May 2, 1913 Details of Process. The following have also been standardised by the Committee:— (1) The amount of sample to be taken for combustion must be between 0*8 and 1'2 grammes. It may be used either (1) as received, (2) air-dried, or (3) after one hour's drying at the boiling point of water; but the analyst's certificate shall in all cases state which of these procedures has been adopted. (2) Water Equivalent. —“ Calibration of Instrument ” (Determination of Constant).—(a) The combustion for this purpose shall be made (where possible) with not less than 1 gramme of pure cane sugar, as supplied by the American Bureau of Standards, which must also have been thoroughly dried in the steam bath before use and then compressed into a block. All other conditions stated below shall be observed. Note —Where cane sugar as above prescribed cannot be obtained, either benzoic or salicylic acid of similar purity (Amer. Bur. St.) may be used in substitution or as a sub- sidiary standard substance. (b) In calculating the result for “calibration," the calorific value of the sugar or other standard substance used shall be that stated on the official certificates accom- panying the specimen, and no allowance other than the radiation correction shall be made. (c) Care must be taken, by using suitable wire, or other- wise, that the ignition current be made as brief as possible, so as not to exceed one second. (3) Standardisation of the Details of the Instrument.—(a) The thermometer for obtaining the rise of temperature on combustion must be sufficiently sensitive to enable direct readings to 0’01 deg. Cent, to be taken (i.e., 100 graduations per degree must be present). (b) The thermometer must have been tested (by detaching the thread) for evenness of bore at all tempera- tures likely to be used. It is preferable to discard altogether a thermometer of which the calibration corrections are large. (c) In reading the thermometer while in position care should be taken not to affect it by heat radiated from the operator's body. To avoid parallax, the use of a catheto- meter, or telescope on a rigidly horizontal axis, at a distance of 6 ft., is preferable. (4) Oxygen to be Used.—This must be of best commercial quality, quite free from hydrocarbons and containing not more than 3 per cent, of nitrogen. It must be introduced into the bomb slowly in order to avoid “ dusting " of the coal. The working pressure (in the case of coal) shall be not less than 25 atmospheres (3601b. per square inch). (5) Stirring.—Some form of mechanical stirring apparatus is preferable, and must have been so adjusted as to give the same degree of agitation in all experiments, but not so violent as to raise the temperature of the water appreciably. (6) Standardisation of Experiment.—(a) The room in which calorimetric work is done should be chosen so as to be as free as possible from temperature fluctuations, and a tank of water should be kept overnight in the room to ensure a uniform supply approximating in temperature to that of the room. (b) To diminish the chance of error, every effort should be made to have the bomb and the outer and inner water all as near the room temperature as possible, and all sources of radiant heat and of draughts must be avoided before commencing a determination. (c) Mode of Operation —A convenient quantity (see sec. 1) of the fuel to be tested shall be weighed with an accuracy of at least a milligramme. Sufficient water shall be placed in the calorimeter vessel to cover the bomb by at least | in. The water in the vessel shall be measured or weighed to within 01 per cent. After assembling all the parts of the calorimeter, stirring shall continue for at least three minutes. (d) Preliminary Temperature Record.—When everything is ready for firing, the “preliminary rate of rise" (B in formula), if any, must be ascertained by reading the thermometer four times with an interval of a minute between each reading. (e) Combustion Period.—The firing current is passed as soon as possible after the last preliminary reading, and thereafter the temperature is watched continuously to find the maximum, but no readings need be registered except as a check on missing the maximum. The maximum is noted, and thereon the operator waits two minutes (until the condition of regular cooling commences). (f) Cooling or Final or Radiation Period.—Five observa- tions of temperature are then taken with an interval of one minute between each reading. The differences should be regular to 0 005 deg., and the “ average difference ” or “final rate of fall" (A in formula) is the difference of the first and fifth readings divided by 4. Thus the operation takes in all nine minutes over and above the time between firing and maximum, or, say, 11 to 12 minutes in all. Everything should be arranged so that no breakdown of this procedure takes places, else the data on which the calculation is founded become somewhat unreliable. (g) At the end of the experiment examine the ash and the inside of the bomb for incomplete combustion. B.—Details in Tabular Form. Volatile matter. Fixed carbon. Ash. Sulphur. C.V. Rate of oxidation at 100 degs. C. per hour. Water in saturated atmosphere. Coalbrook (O.F.S.) 28 8 547 16-0 0'5 11'65 EU. Per cent. 005 Per cent. 9’4 Clydesdale 30 mesh (Springs) 26'9 57'1 160 — — 006 4'2 Do. 60 mesh 26'0 579 161 Density. 1'467 0’07 — Tvl. Delag. 30 mesh 23 5 61'1 15'4 1'435 — 0'15 3’4 Do. 60 mesh 247 59’8 15 5 — — 0 30 — (7) Standardisation of Calculation*—The following new formula has been worked out so as to eliminate the correc- tions for iron wire and for acids (sulphuric and nitric) produced in the combustion, to an extent sufficient to comply with an accuracy of 1 per cent, in the determination as a whole. E = , where F = 1 + A — —, or, alternatively, 539 5 E = (5 + 5A - B). 2,oW5 v ’ E = Result in evaporative units (lb. water/lb. fuel). W = Water equivalent of calorimeter and contents. D = Rise of temperature = maximum minus last pre- liminary reading. A = “ Final rate of fall." B = Preliminary rise. Note.—If, owing to wrong adjustment of the jacket temperature, the preliminary rate is a fall instead of a rise, the factor B must be added (instead of subtracted) in the above formula. In cases where the conditions of section 6 have been rigorously carried out, B may be neglected altogether. (8) Certificates.—The calorific value shall in all cases be stated in evaporative units (pounds water, evaporable at 100 degs. Cent, by 1 lb. fuel); but in addition, and as a subsidiary value, it may be stated in B.T.U. (= 965 EU.) (see also section 1 of “ Details of Process "). (9) Permissible Error.—The difference between the results obtained by two operators using the same sample must not exceed 1 per cent of the calorific value found. 4.—Standard Sizing of Coal. With regard to the question of the grading of coals for commercial use, the Sub-Committee has decided to recommend the following classification and terms:— (a) Round Coal.—All coal which remains on and will not pass through a wire mesh having apertures 2| in. square (6 4cm.) (b) Egg Coal or Cobble Coal.—All coal passing through a wire mesh having apertures 2| in. square, but which will not pass through a wire mesh having apertures 1| in. square (3*2 cm.). (c) Nut Coal.—All coal passing through a wire mesh having apertures 1| in. square, but which will not pass through a wire mesh having apertures | in. square (1’9cm.). (d) Pea Coal.—All coal passing through a wire mesh having apertures f in. square, but which will not pass through a wire mesh having apertures | in. square (0’6 cm ), (e) Duff Coal.—All coal passing through a wire mesh having apertures | in. square. Or, summarising, Classification. Round coal........... Egg or cobble coal .. Nut coal............. Pea Coal............. Duff coal............ Remains on. In. .. 2| .. .. H .. .. | .. .. | .. Passes through. In. 2i I In addition to the above, the use of the term “ run of mine,” is recommended, signifying all sizes of coal mined, the only screening used being that required for the elimination of duff coal. The following definitions are also permitted, so as to cover old-established Transvaal and Natal practice:— “ Large Picked Round ”: Screened over 1| in. sieving. “ Screened Picked Round ” : Screened over f in. sieving. Both of these must have been picked over the picking- belt. Summary of Committee's Experiments. A.—Results. 1. Evolution of volatile matter, in the cases given below, at the boiling point of water is too slow for detection, and even in vacuo does not exceed 0 03 per cent. 2. Ground coal can be completely dried by one hour’s heating at temperatures between 70 degs. Cent, and the boiling point of water. 3. Oxidation of ground coal at the boiling point is slow, and generally not more than 010 per cent, per hour. 4. Absorption of water from the air by dry fine coal is very rapid; in certain cases as much as 2 per cent, per hour. * Poole’s original formula, of which the above is a modifi- cation obtained by a method of mathematical approximation, may be used, by those who prefer it, instead of the method in the text. Carbon on lid counted as volatile: generally 0T per cent., sometimes 0’5 per cent. Ash, 46’7 per cent. SiO2, 32’5 per cent. A12O3,10'2 per cent. CaO, 3'7 per cent. MgO, 6'8 per cent. Fe2O3, traces S and Li (Phosphate is also sometimes present.) C.—Behaviour on Exposure to Air. 1. Freshly-crushed Coalbrook Coal gained 0'4 per cent in first day and 0'6 per cent, altogether, in dry weather (final value 6 0 per cent.). In wet weather, went up to 7 0 per cent.: gave off practically no gas on heating. 2. Clydesdale can be completely dried in three- quarters of an hour at 70 degs. Cent. On exposure in dry weather remains at 2'5 to 2'6 per cent, moisture, and in wet weather at about 3 per cent. Gas extracted by vacuum at 100 = 10’3 c. ft./ton = 0'031 per cent. 3. Transvaal and Delagoa. — Requires one hour at 95 degs. Cent, for complete drying. In dry weather retains 1'8 to 1'9 per cent, moisture, and in wet weather 2'2 per cent. Gas extracted by vacuum at 100 = 6'3 c. ft./ton — 0020 percent. This gas contains only a few per cent, of methane, and is mainly nitrogen and carbon dioxide with a little carbon monoxide. BIRCHENWOOD COLLIERY. Visited by the North Staffordshire Institute. A large number of the members of the North Staffordshire Institute of Mining and Mechanical Engineers joined in an excursion to Birchen wood Colliery, Kidsgrove, on Monday, those present including the president (Mr. Hugh Johnstone). The most con- spicuous features of the operations of the Birchenwood Colliery Company Limited are the coke ovens and by-product plants, the former being capable of car- bonising about 7,000 tons of coal a week and producing 5,000 tons of metallurgical coke. The by-products produced are mainly sulphate and chloride of ammonia, tar, and 65 per cent, benzol. These plants and the monogas producer plant were inspected in detail, under the guidance of Mr. J. R. L. Allott, the manager, and members of his staff. The colliery was last week visited by the King and Queen during their Majesties’ tour of inspection of the industries of North Staffordshire. The Collieries. The Birchenwood Collieries are situated at the northern end of the North Staffordshire coalfield. There are five shafts in use, the principal one being No. 18. This was widened and sunk to its present depth of 430 yards to the Silver Mine seam in 1889. The Silver Mine lies about 40 yards below the Winpenny coal, the latter being the lowest worked at this colliery. The seams worked are in the lower coal series, and lie at a high inclination varying from 30 to 70 degrees., and necessitating in various parts the use of cage dips. Nine seams of coal are at present being worked, varying from 3 ft. to 8 ft. 6 in. The system of working generally adopted is “ heading and drifting." Other shafts in use are No. 4, for pumping and ventilation as a downcast; No. 6, for ventilation as an upcast; and Kids- wood, near Harecastle Station, which is also an upcast. The ventilation is produced by means of two Waddle fans, each 25 ft. in diameter. Two new fans are being put down of the Bumsted and Chandler type, with arrangements for reversing the air. The underground haulages along the main crut and in the West Winpenny slant are operated electrically ; other haulages inbye are operated by compressed-air engines, the main-and-tail system being largely adopted. The steel headgear at Na. 18 pit, which is 93 ft. high to the centre of the pulleys, has been erected within the past 12 months, together with the heapstead and simultaneous decking arrangements by Messrs. Naylor Brothers, Golborne, Lancs. New screening plant is being erected at No. 18 pit by Messrs. Nortons (Tividale) Limited for dealing with an output of 1,500 tons in eight hours, consisting of three mechanically-driven tipplers, three shaking screens and four picking tables. Arrangements have been made at the end of the picking tables so that the coal can either be loaded into trucks or conveyed direct into crushing plant for the coke ovens. The washery is of the Liihrig type, capable of dealing with 1,000 tons of slack in 10 hours. It is arranged in two separate units of 500 tons, each of which can be