On the Common Blowpipe. 321 
candle. We immediately perceive before the orifice a long and coni- 
cal blue flame environed by an outer cone more resembling the com- 
mon flame of a candle, It is at the apex of the blue cone that the 
most intense heat is produced.”’ 
Oxidation takes place when we bring the matter of assay be- 
fore the apex of the exterior flame, where the combustible matter 
coming from the candle has ceased to attract oxygen. The heat 
required for this is only that of incipient redness; and one of the 
larger orifices is best for producing this temperature. 
*‘ Reduction requires a more elevated temperature, which is best 
obtained by one of the finest orifices, which should be introduced 
only within the edge of the flame. A less distinctly blue cone than 
in the former instance, surrounded by a more brilliant one will be 
the result. The matter to be deoxidized is to be supported com- 
pletely within the bright flame just beyond the apex of the blue 
cone ; in this part there is inflammable gas which, of course will take 
oxygen from the substance to be reduced.” 
The size of the mass to be heated, including the flux when one 
is used, should not exceed that of a pepper corn, and when the sub- . 
stance is to be heated alone, the piece should not be much larger 
than a pin’s head. 
To support the trial piece, various substances are used ; such as 
charcoal, platinum wire or foil, small cones of clay, or in fact any 
substance which is infusible and a bad conductor of heat. 
Charcoal is an excellent support in reducing operations, and 
whenever its actions will not taterfere with the result desired. The 
best charcoal for supports is made from light porous wood such as 
pine, and it is important that it should be recently burned. 
Platinum on account of its infusiblility and low conducting power. 
for heat, is the best metallic support that can be used ; wher 
slips of the wire or foil are inserted in glass handles they are very 
convenient, particularly when the action of fluxes is to be examined. 
The handles are easily made by drawing a quill tube to the proper 
size and then placing in one end of it the bit of platinum sealing it 
in its place by directing upon the glass, a flame, by means of a 
blowpipe. 
When the platinum supports are used with fluxes, a little of the 
flux in powder is to be taken up on the extremity of the platinum 
which is slightly moistened to cause it to adhere; then introduce it 
into the flame and fuse it, and while fused touch it to the trial piece, 
Vou. XXXIT.—No. 2. 
