Case-hardening, Electric.
The conversion of the surface of iron into steel by applying a proper
carbonaceous material to it while it is heated by an electric current.
It is a superficial cementation process.
Cataphoresis.
Electric osmore; the transfer of substances in solution through porous
membranes under the influence probably of electrolysis, but without
themselves being decomposed.
Cautery, Electric.
An electro-surgical appliance for removing diseased parts, or arresting
hemorrhages, taking the place of the knife or other cutting instrument.
The cautery is a platinum wire heated to whiteness by an electric
current, and when in that condition used to cut off tumors, stop the
flow of blood and parallel operations. The application is painful, but
by the use of anaesthetics pain is avoided, and the healing after the
operation is greatly accelerated.
The heated wire of the cautery can be used for cutting operations in
many cases where excision by a knife would be almost impracticable.
Synonyms--Galvano-cautery--Galvano-caustry--Galvano-electric,
do.--Galvano-thermal, do.
C. C.
A contraction of cubic centimeter. It is often written in small letters,
as 100 c.c., meaning 100 cubic centimeters.
Cell, Constant.
A cell which yields a constant and uniform current under unvarying
conditions. This implies that neither the electro-motive force or the
resistance of the cell shall vary, or else that as the electro-motive
forces run down the resistance shall diminish in proper proportion to
maintain a constant current. There is really no constant cell. The
constancy is greatest when the external resistance is high in proportion
to the internal resistance.
Cell, Electrolytic.
A vessel containing the electrolyte, a liquid decomposable by the
current, and electrodes, arranged for the passage of a decomposing
current. The voltameter, q. v., is an example.
Cell, Standard Voltaic.
A cell designed to be a standard of electro-motive force; one in which
the same elements shall always be present under the same conditions, so
as to develop the same electro-motive force. In use the circuit is
closed only for a very short time, so that it shall not become altered
by polarization or exhaustion.
Cell, Standard Voltaic, Daniell's.
A zinc-copper-copper sulphate couple. Many forms are used. Sometimes a
number of pieces of blotting paper are interposed between two plates,
one of copper--the other of zinc. The paper next the copper is soaked in
copper sulphate solution, and those next the zinc in zinc sulphate
solution, of course before being put together. Sometimes the ordinary
porous cup combination is employed. The cut shows a modification due to
Dr. Fleming (Phil. Mag. S. 5, vol. xx, p. 126), which explains itself.
The U tube is 3/4-inch diameter, and 8 inches long. Starting with it
empty the tap A is opened, and the whole U tube filled with zinc
sulphate solution, and the tap A is closed. The zinc rod usually kept in
the tube L is put in place, tightly corking up its end of the U tube.
The cock C is opened, which lowers the level of the solution in the
right-hand limb of the U tube only. The tap B is opened and the copper
sulphate solution is run in, preserving the line of separation of the
two solutions. The copper rod is taken out of its tube M, and is put in
place. India rubber corks are used for both rods. As the liquids begin
to mix the mixture can be drawn off at C and the sharp line of
demarcation re-established. In Dr. Sloane's standard cell two test tubes
are employed for the solutions and a syphon is used to connect them.
Oxidation of the zinc lowers the E. M. F.; oxidation of the copper
raises it. With solutions of equal sp. gr. the E. M. F. is 1.104 volts.
If the copper sulphate solution is 1.100 sp. gr. and the zinc sulphate
solution 1.400 sp. gr., both at 15° C. (59°F.), the E. M. F. will be
1.074 volt. Clean pure zinc and freshly electrolyzed copper should be
used.
Fig. 79 STANDARD DANIELL CELL--FLEMING'S FORM.