April 20, 1916. THE COLLIERY GUARDIAN. 755 the true volume of methane in this instance is between 103-5 and 95*3 cu. ft. a minute, a possible difference of 8*2 cu. ft., or nearly 10 per cent., if the errors are all negative. It is the author’s belief that it would be safe to assume a possible error of 10 per cent, in all the reports of volume of 50 cu. ft. or more, and a somewhat larger error for smaller amounts, increasing rapidly to 50 per cent, when the reported methane percentage is near 0’03 per cent. Velocity movements are also less reliable when very low or very high, especially where the cross section is large and irregular. FIELD APPARATUS FOR ASH DETERMINATION. In Bulletin 621A, issued by the United States Geo- logical Survey, a field apparatus for determining ash in coal is described by C. E. Lesher. The apparatus was designed to meet the needs of field parties of the United States Geological Survey, and has been in successful use for three years. It is simple to operate, and if used with a moderate amount of care will determine ash with a possible error of less than 2 per cent. The complete outfit is shown in fig. 1. It weighs, including the case for shipping, about 34 lb. The two articles calling for the most care in selection are the balance and burner. The balance, selected after several others, large and small, were considered, is described in the trade catalogue as a “ pocket scale, capacity 10 grammes, and sensitive to 1 milligramme.” This balance is of the 11 take dowm ” variety, and when closed measures 6 by 2-1- by 11 in. It is easily sensitive to 5 milligrammes, and by careful manipulation can be read to 1 milligramme. The burner adopted for the field outfit is a special type known as “ Barthel’s auto- matic blast lamp ” (fig. 2), which has several decided advantages over the ordinary horizontal flame plumber’s torch. It uses gasoline for fuel; it has the Meker burner, which gives better combustion and a hotter flame than other burners; it is automatic in that it requires no pumping to keep up the air pressure; and in its normal position it gives a vertical flame. This burner can be purchased without the cast iron base and a light skeleton base can be made to support both the burner and the ring stand on which the crucible is set. This base can be easily made by any blacksmith or machinist, and is inexpensive. The lamp has two burners, so that one operator can almost double the number of determinations in a given time. 4 iu«i Fig. 1.—Field Apparatus for Determining Ash in Coal. The sample should first be crushed to J in. size, and then reduced by successive quartering and crushing, so that finally not more than a quarter of a pound remains, all of which will pass through the 10-mesh screen. The sample can be mixed and quartered to advantage on a piece of heavy wrapping paper, or on oilcloth or rubber cloth. Three grammes of the sample are obtained by taking small quantities on the point of the spatula from different places in the bottom pan of the screen. This sample is weighed directly! on the scale pan, and from there brushed with a camel's-hair brush into the lid of the sample tin, and placed in the air bath for drying. Before the coal is burned to ash it should generally be dried, for all coal contains moisture, partly as water adhering to and wetting the particles, and partly as water in the coal itself. The sample should be sub- mitted to a preliminary drying, because evaporation may take place rapidly, as, for instance, in a lignite or low-grade sub-bituminous coal, where loss of water occurs so quickly that the surface of a sample may be seen to crack. The obvious method of removing such a source of apparent discrepancy is, at the beginning, to dry the coal at room temperature until all the moisture that it will give off at that temperature is removed. A sample so treated will undergo the minimum amount of change in moisture content thereafter when exposed to the air. For this reason, the usual laboratory practice is to dry all samples of coal under certain fixed conditions Fig. 2.—Barthel’s Gaso- line Blast Lamp. before they are analysed. The standard practice at the Pittsburg laboratory of the United States Bureau of Mines is to pass a current of air at a temperature of 35 degs. Cent. (95 degs. Fahr.) over the coal until it shows no further appreciable loss of moisture. This process is called air-drying, and the difference in weight before and after drying is called the “ air-dry- ing loss.” In using the field apparatus it is best to dry the samples at 60 degs. Cent. (140 degs. Fahr.) with the sample on the middle shelf, the bulb of the thermometer -J in. above the coal, and the door of the oven open about an inch. It is, of course, impossible by a treatment lasting but an hour to dupli- cate results on air- drying loss that are obtained in the labora- tory under conditions carefully chosen and controlled, and by dry- ing for long periods. Other things being equal, the error in percentage of air-drv- ing loss will vary 'with the amount of mois- ture, being greatest with the highest mois- ture coals. It will not by this method, how- ever, be over 3 or 4 per cent, in a sample of lignite showing an air-drying loss of 30 or more per cent., and as a difference of 3 per cent, in a sample having 30 per cent, air-drying loss makes a difference in the percentage of ash of but 0'03 per cent, if the ash is 5 per cent., or 0’06 per cent, if the ash is 10 per cent., it is evident that the method is sufficiently accurate for the purpose intended. After drying for one hour, the coal is brushed into the balance pan and weighed, the loss in weight being the air-drying loss. An example showing the calculation of this in percentage will be given later. The procedure recommended with the field outfit is as follows :—The air-dry sample is quickly pulverised very fine with the mortar and pestle, and one gramme is weighed out into a crucible. It may not always be necessary or even advisable to use one gramme of coal for burning to ash. If the ash is more than 15 per cent, the time required to burn off completely one gramme is considerably increased, and for this reason | gramme may be used. It should be borne in mind, however, I b at the smaller the sample used the greater is the liability of error in the final result, and when the smaller amount is used extra care should be taken in the weigh- ing of the sample, both before and after burning. For each crucible in use a counterweight of lead foil should first be made, so that by having it on the opposite pan of the balance when the coal and the ash are weighed the actual weighing of the crucible is obviated. The counterpoise should be within one or two milligrammes of the weight of the crucible, and since the latter changes weight with use it is necessary after several days’ use to correct the weight of the counterpoise by addition or subtraction of lead. After the sample is weighed, set the covered crucible upright in a pipestem triangle on the ring stand, adjusting the opening in the triangle by bending the wires so that about two-thirds of the crucible projects below. Adjust the regulating valve of the burner until the flame of the blast lamp is about 3 in. long, and arrange it so that the top of the flame just touches the bottom of the crucible on one side. Increase the heat gradually by turning the regulating valve to the left, so that after 10 minutes the bottom of the crucible is red hot. Ordinarily by this time all moisture and tar are driven off, a portion of the tar having condensed on the upper part of the crucible and on the under side of the lid, and no fumes or smoke can be observed coming off. Lignite and sub-bituminous coal (black lignite), being high in moisture, are apt to sputter when first heated. By heating slowly at first, as described above, with, the flame directed well up against the side of the crucible, this tendency is reduced and the cover prevents loss if the sputtering is slight. At the first evidence of this tendency the heat should be reduced by turning down the flame of the burner. If, however/ the sputtering takes place with sufficient violence to bounce the lid and throw out powdered coal, which will be shown by sparks appearing in the flame outside the crucible, the test is probably spoiled and should be repeated. As soon as all moisture and tar are driven off, remove the cover, tilt the crucible to about 45 degs. on the triangle (fig. 1), and apply the full blast, arranging it so that little or no flame is in front of the crucible to interfere with the free access of air .to the coal. As burning proceeds, the coal will glow, and at times a small flame may be seen playing round inside the crucible. A cover of ash soon forms on top of the mass and checks the speed of burning, so that by stirring every few moments with a fine iron wire, taking care each time to tap the wire before removing it to dislodge adhering ash and coal, the operation is expedited. The crucible should be turned around as the burning proceeds until all the black coating of tar on the inside, formed in the earlier part of the operation, is burned off, and the heating and stirring should be continued until the residue no longer glows, but appears “ dead ” as con- trasted with the hot pulverised coal, which when stirred appears to flow like water or quicksilver. The burning of a one-gramme sample to ash should be completed in .about 30 minutes, after which the crucible should be removed from the flame, covered, and allowed to cool. A convenient holder for the hot crucible is made by bending down the wires of a pipestem triangle (fig. 1) to form legs. When cool enough to handle, the ash may be examined to see whether it contains any unburned black particles. If completely burned it will show no such particles, and its colour will be either greyish white, or, if it contains much iron, pink or red. The crucible containing the ash is placed on one pan of the balance and the lead counterpoise for that crucible on the other, with sufficient weights to balance the ash. Until the operator has had considerable experience in making tests there is always the possibility of mixing the crucibles, their counterpoises, and the sample tins, so that in the end there may be uncertainty as to what sample is represented by the test, or whether the proper counterpoise has been used. To avoid this it is is advisable to mark the crucibles and counterpoises with numbers corresponding to those on the sample tins. A number may be marked on the lead -with a hard pencil or written in ink, and may be written on the bottom of the crucible with a piece of red ochre (haematite); or notches may be filed on the upper edge of the crucible with the comer of a file. These notches should, of course, be made before the lead counterpoise is made. With experience it will be found that if the same order and arrangement is always followed, numbering will cease to be necessary, and there will be no danger of confusing the samples and crucibles. EXPORT REGULATIONS ABROAD. In some ,of the British Colonies and European countries the list of articles which may not be exported has been extended. The list includes the following :— Bahamas.—Prohibited to all destinations other than the United Kingdom, British Possessions and Pro- tectorates : Coal (all kinds except coal shipped as bunkers), coke made in gas works, iron ore of all descriptions, haematite pig iron, iron and steel smelting scraps, railway wagons, and solid drawn steel’tubes. Prohibited to all foreign countries in Europe and on the Mediterranean and Black Seas, other than France, Russia (except through Baltic ports), Italy, Spain and Portugal : Silica bricks, railway material, terneplates, and all receptacles made of terneplates, blast furnace oil, tin-plates, and all receptacles made of tin-plates. Grenada.—Prohibited to all destinations other than the United Kingdom, British Possessions and Pro- tectorates : All coal, except bunkers; magnesite and dead burnt magnesite; silica bricks, terneplates, and all receptacles made of terneplates; blast furnace oil; tin- plates, and all receptacles made of tin-plates. Holland.—Prohibits the export of zinc ore and zinc oxide. Spain.—Limits to 62,000 tons the total quantity of pine logs of a minimum diameter of less than 25 cm. which may be exported. Prohibited Exports.—An Order in Council makes several additions to the exportation restriction and prohibition lists. Among these are :—Prohibited to all destinations : Pig iron of all descriptions; railway material.—steel rails, steel sleepers, steel springs, steel wheels and axles; shipbuilding material— boiler tubes, condenser tubes, steel plates and sectional materials for shipbuilding; steel in bars, angles, rods, and shapes or sections; steel blooms, billets, and slabs; steel bridge, boiler, and other plates not under J in. thick; steel girders, beams, joists, and pillars; steel ingots; steel tubes of all descriptions; steel wire, except barbed and galvanised wire (the exportation of which remains prohibited to all destinations abroad other than British possessions and protec- torates). Prohibited to all destinations abroad other than British possessions and protectorates : Aluminium sulphate and alumino-ferric; files. Prohibited to all foreign countries in Europe and on the Mediterranean and Black Seas, other than France, Russia (except through Baltic ports), Italy, Spain, and Portugal : Asphalt and solid or liquid bitumen; petroleum and its products not already specifically prohibited.