. Inorganic chemistry . because the large amount ofwhite-hot carbon which it contains enables it to reduce—thatis, deprive of oxygen—the great majority of metallic oxides, sothat their oxygen forms carbonic acid, and the metal separates. 444. The tip or point of the outer cone, and to a certainextent its whole external border, is called the oxidising flameof the blowpipe; because metals, and other easily-oxidisedbodies, are rapidly converted into oxides when held in this portion of the flame, in con-sequence of the high tempe-rature to which it elevates the air immediately in contact with it.
. Inorganic chemistry . because the large amount ofwhite-hot carbon which it contains enables it to reduce—thatis, deprive of oxygen—the great majority of metallic oxides, sothat their oxygen forms carbonic acid, and the metal separates. 444. The tip or point of the outer cone, and to a certainextent its whole external border, is called the oxidising flameof the blowpipe; because metals, and other easily-oxidisedbodies, are rapidly converted into oxides when held in this portion of the flame, in con-sequence of the high tempe-rature to which it elevates the air immediately in contact with it. The term oxidisingflame, in truth, is not strictly correct; for it is the heated air, and not the luminous flame, which produces the oxidation; and bodies must be held a little in front of the visible flame in order to secure their oxidation. 445. When the blowpipe is used, the body to be subjected to its action is held in a loop of platinum wire (fig. 48), or placed in a small cup of clay, or in a cavity in a piece. Fig. 48. 148 Chemistry. of charcoal. A stream of air is then sent through the blowpipefrom the mouth, in such a way as to supply the air in an unbrokencurrent. This is effected by closing the lips upon the mouth-piece of the blowpipe, distending the cheeks as a trumpeterdoes, and then blowing; whilst, without letting the cheeks col-lapse, air is simultaneously, or at short intervals, drawn throughthe nostrils. 446. The method of blowing is easily learned. The beginnerfails for a time, in consequence of supplying the current fromhis lungs, the quantity of available air in which is soon exhausted,so that the stream intermits, and the blower is out of secure an unbroken stream, air must at the same time bedrawn in by the nostrils, so as to maintain respiration, and beexpelled by the mouth to feed the current. The cavity of themouth is kept distended, to act as a reservoir, like the sack of abagpipe, whilst, by a slight compressing action of the muscles o
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