Subway, Electric.
A subterranean system of conduits for electric cables. As generally
constructed in this country it includes manholes, q. v., at the street
corners connected by ducts or pipes. These pipes are large enough to
hold a cable. To introduce a cable into a duct, which latter may be two
or three inches in diameter, and from two hundred to six or seven
hundred feet long, a wire or rope is first passed through the duct. This
is done by a set of short wooden rods with screws at the end so as to be
screwed together. Each rod must be shorter than the diameter of the
manhole. A rod is thrust in, another is screwed to it and thrust in, and
thus a set of rods is made to extend as far as desired. In pulling them
out a rope is attached and drawn through. This rope or a larger one is
used in drawing the cable through the duct. A windlass is employed to
draw the rope with cable attached through the ducts.
Sulphating.
In storage battery cells, the formation of a hard white basic lead
sulphate, Pb2 S05. Its formation is due to over-exhaustion of the cells.
As long as the voltage is not allowed to fall below 1.90 volts per cell
little of it forms. As it accumulates it is apt to drop off the plate
and fall to the bottom, thus weakening the plate possibly, and depriving
it of active material, and clogging up the cell. If it carries a film of
metallic lead with it, there is danger of short circuiting the cell.
The presence of some sodium sulphate in the solution is said to tend to
prevent sulphating, or to diminish it.
Sulphur Dioxide.
A compound gas, S O2; composed of
Sulphur, 32
Oxygen, 32
Molecular weight, 64
Specific gravity, 2.21.
It is a dielectric of about the same resistance as air. Its specific
inductive capacity at atmospheric pressure is: 1.0037 (Ayrton).
Synonyms--Sulphurous Acid--Sulphurous Acid Gas.
Sunstroke, Electric.
Exposure to the arc light sometimes produces the effects observed in
cases of sunstroke. It is said that, in the case of workmen at electric
furnaces, these effects are very noticeable. (See Prostration,
Electric.)
[Transcriber's note: Effects are due to ultraviolet light.]
Supersaturated. adj.
A liquid is supersaturated when it has dissolved a substance at a
temperature favorable to its solubility and its temperature has been
allowed to change, the liquid being kept free from agitation or access
of air, provided crystallization or precipitation has not taken place.
It expresses the state of a liquid when it holds in solution more than
the normal quantity of any substance soluble in it.
Surface.
A galvanic battery is arranged in surface when all the positive plates
are connected together and all the negative plates are also connected.
This makes it equivalent to one large cell, the surface of whose plates
would be equal to the aggregate surface of the plates of the battery. It
is also used as an adjective, as "a surface arrangement of battery."