46 On the Blow-pipe. [Jan* 



the oxide, and dried and ignited, it becomes green. With soda 

 in the interior flame it is reduced, and burns with its charac- 

 teristic flame, depositing its oxide upon the charcoal. By this 

 process zinc may be easily detected even in the automolite. 

 Mixed with oxide of copper, and reduced, the zinc will be fixed, 

 and brass be obtained. But one of the most unequivocal cha- 

 racters of the oxide of zinc is to dissolve it in vinegar, evaporate 

 the solution to dryness, and expose it to the flame of a lamp, 

 when it will burn with its peculiar flame. 



Oxide of Iron produces with microcosmic salt or borax in the 

 exterior flame, when cold, a yellowish glass, which is blood-red 

 while hot. The protoxide forms with these fluxes a green glass, 

 which by increasing the proportion of the metal passes through 

 bottle-green to black and opaque. The glass from the oxide 

 becomes green in the interior flame, and is reduced to protoxide, 

 and becomes attractable by the magnet. When placed on the 

 wick of a candle, it bums with the crackling noise peculiar to 

 iron. 



Oxide of Cobalt becomes black in the exterior, and grey in. 

 the interior flame. A small proportion forms with microcosmic 

 salt and with borax a blue glass, that with borax being the 

 deepest. By transmitted light the glass is reddish. By farther 

 additions of the oxide it passes through dark blue to black. The 

 metal may be precipitated from the dark blue glass by inserting a 

 steel wire into the mass while in fusion. It is malleable if the 

 oxide has been free from arsenic, and may be . collected by the 

 magnet ; and is distinguished from iron by the absence of any 

 crackling sound when placed on the wick of a candle. 



Oxide of Nickel becomes black at the extremity of the ex- 

 terior flame, and in the interior greenish-grey. It is dissolved 

 readily, and in large quantity, by microcosmic salt. The glass, 

 while hot, is a dirty dark red, which becomes paler and yellowish 

 as it cools. After the glass has cooled, it requires a large addi- 

 tion of the oxide to produce a distinct change of colour. It is 

 nearly the same in the exterior and interior flame, being slightly 

 reddish in the latter. Nitre added to the bead makes it froth, 

 and it becomes red-brown at first, and afterwards paler. It is 

 easily fusible with borax, and the colour resembles the preceding. 

 When this glass is long exposed to a high degree of heat in the 

 interior flame, it passes from reddish to blackish and opake ; 

 then blackish grey, and translucent ; then paler reddish-grey ^ 

 and clearer ; and, lastly, transparent ; and the .metal is precipi- 

 tated in small white metallic globules. The red colour seems 

 here to be produced by the entire fusion or solution of the oxide, 

 the black by incipient reduction, and the grey by the minute 

 metallic particles before they combine and form small globules. 

 When a little soda is added to the glass formed with borax, the 

 reduction is more easily effected, and the metal collects itself 

 into one single globule. When this oxide contains iron, the 



3 



