154 
ELEMENTARY CHEMICAL MICROSCOPY 
the tiny flame B (reserve flame) employed for microchemical 
work is furnished by a small brass tube inside the Bunsen tube. 
This flame is always burning when the gas is turned on at the 
gas main; its height is regulated by the screw S so as to be from 
3 to 4 millimeters high. If, as often happens, this tiny flame 
cannot be lowered to the proper size, remove the screw S, and 
drop into the hole a small fragment of very soft annealed copper 
wire, replace the screw and turn until the copper fragment has 
been crushed sufficiently to partially obstruct the flow of gas. 
Turning the stopcock A lights the large burner and serves to 
regulate the size of the Bunsen flame. The burner is not sold 
with the ring R, as shown in the figure, but this attachment can 
be made in a few minutes by fastening a bent copper or brass 
wire to a split brass ring which may be raised or lowered and 
maintains its position through friction, or, if possible, a heavier 
ring with thumb-screw is substituted for the simple ring. This 
wire ring is useful as a support when moderately long heating 
must be practiced or when evaporations over a tiny flame at 
moderate temperatures are required. 
For the production of higher temperatures than are possible 
with the flame of the Bunsen burner, a blowpipe will be found 
