By JAMES W. PAUL. INTRODUCTION. Within recent years there has come into use in metal mines and in many coal mines in the United States a type of open-flame cap lamp for burning acetylene gas, the gas being made within the lamp by the use of calcium carbide and water. In some nongaseous coal mines this type of lamp has almost entirely taken the place of the miners' open-flame oil lamp, and in many metal mines it has replaced candles. The number of acetylene lamps in daily use in the mines of the United States is estimated at fully 300,000; 60 per cent of the lamps used in nongaseous coal mines and 15 to 20 per cent of those in metal mines being acetylene lamps. These acetylene-burning lamps are known to miners and to the trade as "carbide lamps." They are used in metal mines and in nongaseous coal mines, the use of safety lamps being required in gaseous coal mines. Acetylene gas has long been used for lights on bicycles and automobiles and in some houses. When acetylene gas was first used in lighting houses, bad machinery or improper care of the plants caused many accidents, and explosions followed by fires resulted in much loss of property. Some persons who are considering the use of carbide lamps in mines may remember some of these accidents and desire information regarding the safety of the lamps. For the benefit of such persons the Bureau of Mines, which is directed by law to carry on investigations to make mining safer, issues this circular. A carbide lamp gives more light than a candle or miner's oil lamp, and the reflector used on some carbide lamps concentrates the light. Thus the careful miner has better protection from roof falls because he can detect dangerous roof conditions that he would not easily detect with an oil lamp or candle. The introduction of carbide lamps in metal mines and in nongaseous coal mines that are well ventilated, should materially reduce the number of accidents resulting from poor light. Compared with a miner's oil-burning lamp or a candle, the time required for adjusting the carbide lamp to keep it burning properly is more than offset by the increased amount of work that may be performed in a day by its use. 94107°-15 5 The author of this circular, who has seen carbide lamps in use in mines and has tested them in the laboratory, calls attention here to some features of these lamps and the precautions to be taken in using them. GENERAL FEATURES OF THE LAMPS. Several models of carbide lamps are for sale, but certain features of design are common to all. A carbide lamp usually has two parts, one above the other, which can be screwed together. The top part holds water and the bottom part holds the carbide. The feed of water from the top part is regulated by a valve worked from the top or side of the lamp. A tube or compartment leads from the bottom part to the burner. In this tube or compartment are screens or felt to strain out solids and to keep them from clogging the burner tube. By means of a hook or handle the lamp may be fastened to the miner's cap, carried in the hand, or stuck on timber. Some models have reflectors back of the burner, others have none, and still others have the flame surrounded with a glass set in a frame. MANUFACTURE OF CARBIDE. To make carbide, ordinary lime (calcium oxide) and coke are finely ground, well mixed, and heated very hot in an electric furnace until the calcium in the lime unites with the carbon of the coke. The solid product formed is known to chemists as calcium carbide (CaC2), and to miners as carbide. ACETYLENE GAS. When water comes in contact with carbide a chemical action takes place; heat is given off, and common slaked lime and acetylene gas (C2H2) are formed. In practice, 1 ounce of good carbide makes about 500 (496.8) cubic inches of acetylene gas. The heat from action of the water on the carbide makes the bottom part of the lamp, and the carbide, water, and slaked lime in it, get warm. Acetylene gas burns in air with a very bright flame. It does not contain oxygen, and to burn it oxygen must be supplied. The oxygen needed to support the flame comes from the air. When acted on by moisture or water ordinary carbide gives a strong, peculiar odor, somewhat like that of garlic. This odor, which is easily recognized by anyone who has smelled it, is chiefly due to impurities in the carbide. OTHER GASES FORMED BY ACTION OF WATER ON CARBIDE. Gases other than acetylene are formed by the action of water on good carbide, but the quantities formed are so small that the products of their burning in the flame of the lamp are not in the least dangerous. Small quantities of phosphuretted hydrogen and hydro |