reaction of the potash will be destroyed. This is likewise the case
with the presence of lithia, for its peculiar red color will destroy
the violet of the potash. Therefore in making investigations with the
silicates which contain potash, the violet color of the latter can
only be discerned when they are free from soda and lithia.


B. THE BLUE COLOR.

(_a._) _The Chloride of Copper._--Any of the chlorides produce a blue
color in the blowpipe flame, or any salt which contains chlorine will
show the blue tint, as the color in this case is referable to the
chlorine itself. There are, however, some chlorides which, in
consequence of the peculiar reactions of their bases, will not produce
the blue color, although in these cases the blue of the chlorine will
be very likely to blend itself with the color produced by the base.
The chloride of copper communicates an intense blue to the flame, when
fused on the platinum wire. If the heat be continued until the
chlorine is driven off, then the greenish hue of the oxide of copper
will be discerned.

(_b._) _Lead._--Metallic lead communicates to the flame a pale blue
color. The oxide reacts in the same manner. The lead-salts, whose
acids do not interfere with the color, impart also a fine blue to the
flame, either in the platina forceps, or the crooked wire.

(_c._) _Bromide of Copper._--This salt colors the flame of a
bluish-green color, but when the bromine is driven off, then we have
the green of the oxide of copper.