42 On the Bloio-pipe. [Jan. 



fused with an additional quantity of soda, which will be absorbed 

 by the charcoal, and the spot where the absorption has taken 

 place is to be strongly ignited by a tube with a small aperture. 

 By continuing this ignition, the portion of metal which was not 

 previously reduced will now be brought to a metallic state ; and 

 the process may be assisted by placing the bead in a smoky 

 flame, so as to cover it with soot that is not easily blown off. 



The greatest part of the beads which contain metals are fre- 

 quently covered with a metallic splendour, which is most easily 

 produced by a gentle, fluttering, smoky flame, when the more 

 intense heat has ceased. With a moderate heat the metallic 

 surface remains ; and by a little practice it may generally be 

 known whether the substance under examination contains a 

 metal or not. But it must be observed that the glass of borax 

 sometimes assumes externally a metallic splendour. 



When the charcoal is cold, that part impregnated with the 

 fused mass should be taken out with a knife, and ground with 

 distilled water in a crystal, or, what is much better, an agate 

 mortar. The soda will be dissolved ; the charcoal will float, and 

 may be poured off; and the metallic particles will remain in the 

 water, and may be examined. In this manner most of the metals 

 may be reduced. 



Relations of the Earths and Metallic Oxides before the Bloiv-pipe. 



I. THE EARTHS. 



Banjtes, when containing water, melts and spreads on the 

 charcoal. Combined with sulphuric acid, it is converted, in the 

 interior flame, into a sulphuret, and is absorbed by the charcoal, 

 with effervescence, which continues as long as it is exposed to 

 the action of the instrument. 



Strontites. If combined with carbonic acid, and held in small 

 thin plates with platina forceps in the interior flame, the carbonic 

 acid is driven off'; and on the side of the plate farthest from the 

 lamp a red flame is seen sometimes edged with green, and 

 scarcely perceptible but by the flame of a lamp. Sulphate of 

 strontites is reduced in the interior flame to a sulphuret. Dis- 

 solve this in a drop of muriatic acid, add a drop of alcohol, and 

 dip a small bit of stick in the solution ; it will burn with a fine 

 red flame. 



Lime. The carbonate is easily rendered caustic by heat ; it 

 evolves heat on being moistened, and is afterwards infusible 

 before the blow-pipe. The sulphate is easily reduced to sul- 

 phuret, and possesses, besides, the property of combining with 

 fluor at a moderate heat, forming a clear glass. The fluor should 

 be rather in excess. 



Magnesia produces, like the strontites, an intense brightness 

 in the flame of the blow-pipe. A drop of solution of cobalt being 

 added to it, and it being then dried and strongly ignited, a faint 



