OF CENTRAL CANADA PART I. 



27 



FIG. 32. 



cause it, if an oxide, to combine with a larger amount of oxygen ; or 

 (3) to reduce it, either to the metallic state, or to a lower degree of 

 oxidation. The first and second of these effects may be produced 

 by the same kind of flame, known as an oxidating flame (or O. F), 

 the position of the substance being slightly different : whilst the third 

 effect is obtained by a so-called reducing flame (or R. F ), in which 

 the yellow portion is developed as much as possible, and the substance 

 kept within it, so as to be off from contact with the atmosphere. 



An oxidating and fusion flame is 

 thus produced. The point of the 

 blowpipe is inserted well into the 

 flame of the lamp or candle under 

 use, so as almost to touch the sur- 

 face of the wick. The deflected 

 flame is thus well supplied with 

 oxygen, and its reducing or yellow portion becomes obliterated. It 

 forms a long narrow blue cone, surrounded by its feebly luminous 

 mantle. The body to be oxidized should be held a short distance 

 beyond the point of the cone, as in FIG. 32 ; but to test its fusion, 

 it must be held in contact with this, or even a little within the 

 flame. In thiia r position many substances, as those which contain 

 lithia, stronia, baryta, copper, &c., impart a crimson, green, or other 

 colour to outer or feebly luminous cone 



-*<^. For the production of a reducing flame 



the orifice of the blowpipe must not be too 

 large. The point is held just on the out- 

 side of the flame, a little above the level 

 of the wick, as shown in FIG. 33. The 

 flame in its deflected state, then retains 

 Fl - 33 - the whole or a large portion of its yellow 



cone. The substance under treatment must be held within this 

 (although towards its pointed extremity) so as to be entirely excluded 

 from the atmosphere ; whilst at the same time, the temperature is 

 raised sufficiently high to promote reduction. As a general rule, 

 bodies subjected to a reducing treatment should be supported on 

 charcoal. 



For ordinary experiments, such as testing the relative fusibility, 

 &c., of minerals, the blowpipe may be used x with the flame of a com- 



