BUNSEN BURNER, a burner so designed that it mixes a predetermined quantity of air with the stream of gas before it is ignited. If the proportions of gas and air are correct the result ing flame is hot and non-luminous. The invention of this widely used burner is ascribed to Robert Wilhelm von Bunsen (q.v.), though recent investigations prove that the credit for the actual design should go to Peter Desdga, if not to Michael Faraday (q.v.) who had previously designed an adjustable burner on this principle.
The simple idea, attributed to Bunsen, of admitting air into a tube along with gas to produce a hot non-luminous flame, is in corporated in the construction of millions of burners for heating and lighting purposes. The Bunsen flame results when air and gas are admitted in the proportion of about three volumes of air to one of gas; these produce the inner lower cone of the flame, evolving a mixture of water-vapour, carbon monoxide, hydrogen, carbon dioxide and nitrogen. The water-gas and nitrogen reach the outer combustion zone where the water-gas becomes burned up by the ordinary, or secondary, air supply. Various effects, as fusion, oxidation and reduction are obtainable with the flame and blowpipe. Certain metallic salts impart characteristic coloration to the colourless flame.
Varieties of laboratory Bunsens are chiefly distinguished by improvements in the control and mixing of the air and gas, giving greater heating powers and enabling different sizes of flames to be obtained. Among the most efficient of these are the Meker and the Fisher burners. Numerous fitments are made to go on the top of the tube for spreading the flame, or taking special holding devices. Several designs avoid the fault of the ordinary central gas jet, which may become choked up by matter falling down the tube, the gas being brought in at the side and the air at the bottom, with a coned regu lator raised and lowered by a knob. Marshall's burner has a flat regulator working beneath the base, as seen in the sectional view. Burners may be constructed to burn coal-gas, oil-gas, acety lene or natural gas.
The Bunsen burners fitted to incandescent lights, the so-called Welsbach burner (q.v.), require careful manufacture to ensure satisfactory results. The jet or injector must be exactly central with the Bunsen tube, and the in terior surfaces finished smoothly and straight, with no raggedness at the orifice, otherwise the flame will not "fit" and heat the mantle properly. Passage through gauze or several fine holes assists in mixing, while a special mix ing chamber is often included. A Venturi tube has the effect of increasing the velocity of the flow of gas, so enabling it to suck in more air. High-pressure gas lighting has given increased efficiency by reason of the increased velocity also secured. Air-blast for furnaces constitutes another way of increasing air supply and ob taining higher temperatures. The practice of preheating is another advance in aiding perfect combustion ; instead of passing cold air into the Bunsen tube the lamp has a heating tube or chamber, while in some the mixture is preheated. Furnaces are built with recuperative action to heat the air supply from the furnace itself.
(F. H.)