BLOWPIPE, a tube or pipe arranged to blow air or a gas against a flame, as of a gas-jet, so that it may be concentrated upon a small surface. Its most usual form is described in the article on blowpipe analysis (q.v.). It is employed by jewelers and goldsmiths in the work of soldering, and by other workers on small metallic objects; by the glassblower in making thermometers, barometers and other glass instruments ; by the enameler; and in deed wherever it is required to subject a small body to a strong heat. It has undergone a variety of improvements in the hands of the chemist, to whose researches it has proved an excellent auxiliary. Wollaston's portable blow pipe is formed of three pieces fitted into one another when in use, but which may be taken down and made to slide within each other. Most laboratory blowpipes have a hollow bulb or enlarged part at the end, to condense the vapor of the breath. To prevent corrosion from moisture, the bulb is made of silver, sheet-tin or the like. Sometimes two pipes are mounted on a table so that both may be directed on the same object, a bellows under the table furnish ing the power. A little practice is necessary to enable the operator to keep up a constant blast for any length of time the current of air be ing propelled through the pipe by the muscular exertion of the checks, while respiration is carried on through the nose. But when the
process has to be long continued, the current of air is supplied by bellows. This is the form commonly used by glassblowers. The gas blow pipe, commonly called the oxyhydrogen blow pipe, is a very important and intensely powerful variety, whose structure is due to Mr. Newman of London. Sir Humphrey Davy suggested the employment of other gases instead of common air, and Dr. Clarke of Cambridge adopted the suggestion. Dr. Clarke found that a mixture of two volumes of hydrogen and one of oxygen produced an intense heat. These gases are con tained in a bladder attached to the end of a pipe which leads into a vertical cylinder, in which is fitted a piston, working through a collar at the top. By the action of this piston the gas from the bladder is compressed into a copper chamber, and thence issues to the flame through an ordinary blowpipe nozzle. To guard against explosions, the gases are kept in separate holders, and by means of valves in the burner are mixed only at the instant of burning. There are various other forms of blowpipe, and many uses to which they may be applied. One of the most unique is the electric blowpipe, which sends a stream of air or gas particles from the point of a charged conductor. For information on the subject consult Plattner, 'On the Blow pine.)