On the Common Bloivpipe. 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 jiame. 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 

 Vi'henever its actions will not interfere 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; and when, 

 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, 



Vol. XXXII.— No. 2. 41 



