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30 MODERN MAGIC LANTERNS.
interchange of fittings, the screw threads at the mouth of
the oxygen cylinders are of a different pitch to those for
hydrogen ; in consequence, fittings made for an oxygen
cylinder cannot be screwed into one made to contain hydrogen,
nor is the reverse of this possible. To distinguish the
cylinders, those intended for the reception of oxygen are
usually painted black, those for hydrogen bright red, and
this rule should apply not only to the cylinders themselves,
but also to the painted portions of the gauges, regulators,
and jet taps. If, in addition to this, black rubber tubing is
used for oxygen and red for hydrogen, the connections
will become far clearer, and any alterations necessary in
them, however complicated the system, will be made with
little chance of mistake.
The gas can be used direct from the cylinders to the jet
without the intervention of any regulator, but this is not
advisable, and unless absolutely necessary should not be
attempted. If, however, circumstances necessitate such a
course, all regulation of the supply of gas must be done at
the valve of the cylinder itself,
the taps at the jets being
left full on ; on no account must
the jet tap be turned off.
If this were done the pressure
'00-0111k:1
Fig. 22. FINE ADJUSTMENT VALVE.
in the cylinder would rapidly
accumulate behind the jet, and
the tubes would be blown off,
or, if tied on, burst. Where
the regulation has to be
done at the cylinder, a form of
screw-down valve in which
the adjustment can be regulated
to a nicety will be found
a convenience, one of these is
shown in Fig. 22. Biunial and
triple lanterns necessitate the
use of regulators on the cylinders.
Cylinder valves are worked by means of a key, which
is generally of the form used by piano tuners, Fig. 23, or of
a plain lever pattern, Fig 24. The lever key, while handy
Fig. 23. .PIANO KEY.
Fig. 24. LEVER KEY.
COMPRESSED GASES. 31
for turning on and adjusting the flow of the gas, possesses
the drawback that its powerful leverage in turning off the
gas may cause injury to the valve seating ; to obviate this
0
Fig. 25. BRIN'S HINGED LEVER KEY.
Messrs. Brin have introduced a hinged lever key, Fig. 25,
which can be used as a lever key for opening the valve, but
which when applied to close the valve folds up into the
piano key form.
It should be hardly necessary to point out that cylinders
in use should be prevented from rolling about, they are
most convenient when held erect in a box with firm
footing, if simply leaned up against anything they should
be tied.
No oil or other lubricant should on any account be
allowed to come into contact with the cylinder valves or
fittings, and when cylinders are used in the vertical position
care must be taken to prevent grit or dirt of any kind falling
into the valve opening.
When a cylinder of gas is obtained, unless it is going
to be used at once, the valve should be tested for leakage
by plunging it under the surface of water, when, if there
is a leak, bubbles of gas will manifest themselves. An
efficient but not so cleanly method consists in moistening
the finger with saliva and making a slight film or bubble
over the mouth of the valve. If there is a leakage the
bubble will be distended.