BLOWPIPE, a small instrument used in the arts for glass blowing and solder ing metals, and in analytical chemistry and mineralogy, for determining the na ture of substances by the action of an intense and continuous heat. Its utility depends on the fact, that when a jet of air or oxygen is thrown into a flame, the rapidity of combustion is increased, while the effects are concentrated by diminish ing the extent or space originally oc cupied by the flame.
The blowpipe generally consists of a conical tube of metal, about eight inches long, closed at the wider or lower end, but open at the narrow or upper end, which latter constitutes the mouthpiece, and is turned over to admit of the lips closing perfectly round it. Near the lower end, a small tube, fitted with a small platinum tip, is inserted in the large tube —the space below being intended as a chamber for condensing the moisture of the breath, and through this tip a fine current of air can be projected against the flame experimented with.
Where high temperatures are required mechanical blowpipes are resorted to.
Substances under examination before the blowpipe are generally supported either on wood-charcoal or platinum—the latter in the condition of wire or foil. In applying the blowpipe test, the body to be examined is either heated alone, or along with some flux or fusible sub stance; this being added, in some cases, for the purpose of assisting in the reduc tion of metals from their ores and other compounds: in others, for the production of a transparent, glassy bead, in which different colors can be readily observed. When heated alone, a loop of platinum wire, or a piece of charcoal, is generally employed as a support; the former when the color of the flame is to be regarded as the characteristic reaction, the latter when such effects as the oxidation or re duction of metallic substances are to be observed.
The following metals are reduced from their compounds when heated with car bonate of soda on charcoal in the inner flame of the blowpipe: viz., nickel, cobalt, iron, molybdenum, tungsten, copper, tin, silver, gold, and platinum. When com pounds of zinc, lead, bismuth, arsenic, antimony, tellurium, and cadmium are similarly treated, these metals are also formed, but being volatile, pass off in vapor at the high temperature to which they are exposed.
The blowpipe has been long used by goldsmiths and jewelers for soldering metals, and by glass blowers in fusing and sealing glass tubes, etc.; it has also been applied in qualitative analysis for many years, but more recently chemists have devoted their attention to its use, and have even employed it with great success in quantitative chemical analysis.
The oxyhydrogen blowpipe is an ar rangement by which a jet of oxygen and hydrogen, in the proportions to form water, is ignited and directed against any object. The most intense heat is produced, most of the metals being volatilized when placed in it, and even the diamond changes into ordinary car bon, and is burned when exposed to its flame. When a cylinder of quicklime is heated by it, a most dazzling light is pro duced, rivalling the electric light in bril liancy, and known as the calcium light.