To introduce substances into gases, a deflagrating spoon is required.
It may be bought for half-a-crown; but an instrument equally useful
may be made as follows: cut a piece of sheet copper somewhat larger
than a sixpence, and bend it into a shallow, cup-like form; twist four
fine brass wires, each nine inches long, tightly together, leaving an
inch at the extremities, which must be spread to hold the copper, as
the strings or chains of a balance support the scale-pan. To complete
it, take a piece of sheet-lead, the size of a penny-piece; make a hole
through the centre large enough to admit the twisted wires, but, at the
same time, retaining them firmly in their position: then, if the wires
will not rest in the lead by adhesion, the hole may be enlarged, the
wire put in, and secured by a piece of solder. The spoon being then let
down through the mouth of a bottle, the circular piece of lead rests
upon and stops the mouth.