THE COLLIERY GUARDIAN AND JOURNAL OF THE COAL AND IRON TRADES. Vol. CXI. FRIDAY, JANUARY 14, 1916. No. 2872. A New Firedamp Detector. By GEORGE The new gas detector developed at the Pittsburg Experiment Station of the Bureau of Mines, and illus- trated in the drawings, will, it is believed, fill the need for a device for detecting gases in mines and other places, that is simple in construction and operation, light in weight, strong and accurate. It is scarcely necessary to add that a real need exists for such a device, and that'a machine that fulfils these require- ments will find widespread employment. Fig. 1 shows the detector assembled ready for use. Brass and aluminium are used throughout in the con- struction, except the glass tube on the right. In less than two minutes (the time required to make a test), the water level automatically drops in the glass tube, show- ing the percentage of methane present. The machine illlustrated in fig. 1 was devised to be supplied with the small amount of electrical energy, required to operate it, from a miner’s cap lamp battery A. BURRELL.* window E, which is amply protected against breakage by being imbedded in the easting y. A hook T is pro- vided for carrying the instrument. The aluminium scale, as shown, is provided with four separate gradua- tion columns. One graduation is for indicating percentages of methane or natural gas in air, another for showing percentages of gasoline vapour in air, a third for hydrogen in air, and the fourth for coal gas in air, i.e., gas made by destructive distillation of coal. In other words, the ins', rument is not limited to use in mines for detecting methane (firedamp), but can be used for detecting any combustible gas in air, such as gasoline vapour ;in air around places where gasoline is stored, hydrogen around storage battery installations, natural gas and coal gas in buildings, etc. The weight of the instrumen. is 1'4 lb. When not in use it rests on the flat-bottomed base. The instrument may be regarded as a U tube, of which other words, comes back to its original position. In falling to Q, the water sucks in a sample of the air to be tested. This sample of air rests in the combustion space above the water at Q, and in contact with .he platinum spiral F. The valve is then closed, and the platinum spiral F is electrically heated. Any combustible gas in the sample begins to burn immediately, and at the. end of two minutes is completely consumed. Next, the electric current is turned off, and the instrument is agitated, thus shaking the water into the combustion space above Q and cooling the gases. The water column in C falls immediately to a point opposite the graduated scale (corresponding to the percentage of methane present), thus showing the percentage of methane present in the sample. The principle of the operation is this : Methane on reacting with oxygen, burns as follows : 1 volume 2 volumes 1 volume CH, + 2 0., = i O.) + 211,0 In other words, one volume of methane reacts with two volumes of oxygen and forms one volume of carbon dioxide; or, during combustion, three volumes have con- tracted to one volume, the wafer vapour (H20) Fig. 2. Sectional View of Detector. Fig. 1. Detector Ready for Use. Fig. 3. Detector for Combustible Gas in Air. d — d - 7s or hand lamp battery. All that is needed is to switch the current from the miner's lamp (which can be burning at the same time) to the gas detector for a space of less than two minutes. The device can be used for detecting methane (in mine air), natural gas, gasoline vapour, gas made by destructively distilling coal, and hydrogen in air. It can also be used for detecting carbon monoxide in flue gas or air, and for water gas, or any other combustible gas, in air. Referring to fig. 2, the detector consists essentially of seven parts : The aluminium castings x and y, the standard brass tubing A, the stout gauge glass c, the aluminium scale o, the brass reservoir N, and the brass top piece P carrying a platinum wire F. A valve V seats itself into this top piece P, and two binding posts, M and N, are shown connecting with this platinum wire. Electrical connections are made to the binding posts M and N for heating the platinum wire. »The latter, when hot, can be observed by peering through the small glass * Chemist in Charge of Gas Investigations, United States Bureau of Mines. the tubes A and C form the two branches. The arrow at B shows the connection between them. To make the device ready for use, the top piece P is unscrewed, and water is poured into A, until it fills the two branches, A and C, and rests in C at the point S, the zero point of the scale. The water will have then found its level at a corresponding point in A (at Q), just below the platinum wire F. To make a determination of combustible gas in air, ■say, of methane in mine air, one opens the valve V, and, by means of a short rubber tube attached to R, blows (by means of the mouth) gently into the reservoir H, thus depressing the water column in C to some point in B, and forcing the water column up above Q until water appears in the li: tie cup K. It is not necessary to see the water appear in K, its arrival being notified by a slight click in the valve V. Next, the rubber tube (not shown) attached to R is pinched with the fingers, and the instrument is raised to the roof of the mine or moved to any place where the sample is to be collected, the rubber tubing being then released. The water immediately falls to the point Q, and rises in C to the point S; in condensing and occupying a merely inappreciable space. Hence, if a mixture of methane and ,air be burned in the gas detector, a contraction in the volume of the sample takes place. The water therefore rises in the reservoir space above Q, and falls correspondingly in the glass tube C, i.e., falls to a point, on the scale, that shows the percentage of methane present. Even so small a percentage as 0'1 per cent, of methane or other com- bustible gases can be detected. The platinum wire can be heated by means of the storage battery of a miner’s electric cap lamp. This battery may be either carried on a man’s belt, as is the usual custom in handling these lamps—the current being simply switched from the lamp to the detector as tests are made—or it may be carried in the hand, and connected to the detector by means of suitable leads. The essential stages of the operation in making a test are the following :— (1) The. operator blows into the instrument, thereby filling the combustion .space with water. (2) Next the water above Q is allowed to fall, thus drawing a sample of the air into the apparatus.