Spark Tube.
A tube used as a gauge or test to determine when the exhaustion of the
vacuum chamber or bulb of an incandescent lamp is sufficiently high.
The interior of the tube is connected with the interior of the bulb or
chamber of the lamps in process of exhaustion, and hence shares their
degree of exhaustion. From time to time connections with an induction
coil are made. When the exhaustion is carried far enough no discharge
will take place through the vacuum. As long as the tube acts like a
Geissler tube the exhaustion is not considered perfect.
Specific Heat of Electricity.
The heat absorbed or given out by a fluid in passing from one
temperature to another depends on its specific heat. In the Peltier and
the Thomson effects. q. v., the electric current acts as the producer of
a change of temperature, either an increase or decrease as the case may
be. This suggests an absorption of and giving out of heat which amount
of heat corresponding to a current of known amount is determinable, and
may be referred to any unit of quantity such as the coulomb. This or
some equivalent definite quantity of heat it has been proposed (Sir
William Thomson) to term the Specific Heat of Electricity.
Spent Acid.
Acid which has become exhausted. In a battery the acid becomes spent
from combination with zinc. It also loses its depolarizing power, if it
is a chromic acid solution or of that type, and then may be said to be
spent.
Spent Liquor.
The liquor of a plating bath which has become exhausted from use, the
metal it contained being all or partly deposited.
Sphygmograph, Electric.
An electric apparatus for recording the beat of the pulse, both as
regards its rate and strength.
Sphygmophone.
An apparatus for examination of the pulse by the microphone and
telephone.
Spiders.
Core-discs of a dynamo or motor armature are sometimes perforated with a
large central aperture, are fastened together with insulated bolts, and
the whole mass is secured to the shaft by three- or four-armed spiders.
These are like rimless wheels, the ends of their arms being secured to
the hollow cylinder constituting the armature core, and a central
aperture in their hub receiving the shaft.