A carbon for arc lamps with a central core of softer carbon than the exterior zone. It fixes the position of the arc, and is supposed to give a steadier light.

Synonym--Concentric Carbon.

Carbon Holders.

In arc lamps, the fixed clamps for holding the ends of the carbons.

Carbonization.

The igniting in a closed vessel, protected from air, of an organic substance so as to expel from it all the const.i.tuents except part of the carbon; destructive distillation. (See Carbonized Cloth.)

Carbonized Cloth.

Cloth cut in discs and heated in vessels protected from the air, until reduced to carbon. The heating is sometimes conducted in vacuo. They are placed in a pile in a gla.s.s or other insulating tube, and offer a resistance which can be varied by pressure. The greater the pressure the less will be the resistance, and vice versa.

Carbon Dioxide.

A compound gas, CO2. It is composed of Carbon, 12 parts by weight.

Oxygen. 32 "

Specific gravity, 1.524 (Dulong and Berzelins).

Molecular weight, 44.

It is a dielectric of about the resistance of air. Its specific inductive capacity at atmospheric pressures is 1.000356 (Boltzmann).

1.0008 (Ayrton).

Synonyms--Carbonic Acid--Carbonic Acid Gas.

108 STANDARD ELECTRICAL DICTIONARY

Carbon, Volatilization of.

In arc lamps the heat is so intense that it is believed that part of the carbon is volatilized as vapor before being burned or oxidized by the oxygen of the air. The same volatilization may take place in incandescent lamps which are overheated.

Carcel.

The standard of artificial illumination used in France. It is the light yielded by a standard lamp burning 42 grams (648 grains) of colza oil per hour, with a flame 40 millimeters (1.57 inch) in height. One carcel is equal to 9.5 to 9.6 candles.

Carcel Lamp.

The lamp giving the standard of illuminating power. The wick is cylindrical, giving an Argand or central draft flame. It is woven with 75 strands, and weighs 3.6 grams (55.5 grains) per decimeter (3.9 inches) of length. The chimney is 29 centimeters (11.3 inches) high, 47 millimeters (1.88 inch) in diameter at the bottom, contracting just above the wick to 34 millimeters (1.36 inch).

Carcel Gas Jet.

A standard Argand gas burner, made with proper rating to give the light of a definite number of carcels illuminating power. Cognizance must be taken of the quality of the gas as well as of the burner used.

Carrying Capacity.

In a current conductor, its capacity for carrying a current without becoming unduly heated. It is expressed in amperes. (See Wire Gauge, American.)

Cascade.

The arrangement of Leyden jars in series on insulating supports, as described below.

Cascade, Charging and Discharging Leyden Jars In.

An arrangement of Leyden jars in series for the purpose of charging and discharging. They are placed on insulating supports, the inner coating of one connected with the outer coating of the next one all through the series. The actual charge received by such a series, the outer coating of one end jar being grounded, and the inner coating of the other being connected to a source of high potential, or else the same being connected to electrodes of opposite potentials is no greater than that of a single jar, but a much higher potential difference can be developed without risk of perforating the gla.s.s of a jar. The difference of potential in each jar of the series is equal to the total potential difference divided by the number of jars. The energy of discharge is equal to the same fraction of the energy of a single jar charged with the same quant.i.ty.

[Transcriber's note: The equal distribution of potential a.s.sumes all the jars have the same capacity. The charge on all jars is the same since they are in series.]

109 STANDARD ELECTRICAL DICTIONARY.

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.

Cataph.o.r.esis.

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 pa.s.sage 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.