Chemical Equivalent.

The quotient obtained by dividing the atomic weight, q. v., of an element by its valency, q. v. Thus the atomic weight of oxygen is 16, its valency is 2. its chemical equivalent is 8. It is the weight of the element corresponding to a unit weight of hydrogen, either as replacing it, or combining with it. In electro-chemical calculations the chemical equivalent is often conveniently used to avoid the necessity of dividing by the valency when atomic weights are used. The latter is really the better practice. The atomic weights in the old system of chemical nomenclature were chemical equivalents.

117 STANDARD ELECTRICAL DICTIONARY.

Chemical Recorder.

A form of telegraphic recorder in which the characters, often of the Morse alphabet or some similar one, are inscribed on chemically prepared paper by decomposition affecting the compound with which the paper is charged. In the original chemical recorder of Bain, the instrument was somewhat similar to the Morse recorder, except that the motionless stylus, S, always pressing against the paper was incapable of making any mark, but being of iron, and the paper strip being impregnated with pota.s.sium ferrocyanide, on the pa.s.sage of a current a stain of Prussian blue was produced where the stylus touched the paper. The current pa.s.ses from the line by way of the iron stylus, through the paper, and by way of a bra.s.s surface, M, against which the paper is held and is pressed by the stylus, to the earth. This recorder is extremely simple and has no part to be moved by the current. The solution in which the paper is dipped contains a mixture of pota.s.sium ferrocyanide and ammonium nitrate. The object of the latter is to keep the paper moist. In recent recorders a solution of pota.s.sium iodide has been used, which gives a brown stain of free iodine, when the current pa.s.ses. This stain disappears in a few days.

Fig. 83. BAIN'S TELEGRAPH EMPLOYING CHEMICAL RECORDER.

In the cut, R is the roll of paper, B is a tank of solution with roll, W1, for moistening the paper; M is the bra.s.s surface against which the stylus, S, presses the paper, P P; W, W are feed rollers; T is the transmitting key, and zk the battery; Pl, Pl are earth plates. The apparatus is shown duplicated for each end.

118 STANDARD ELECTRICAL DICTIONARY.

Chemistry.

The science treating of atomic and molecular relations of the elements and of chemical compounds of the same.

Chimes, Electric.

An apparatus employed to ill.u.s.trate the principles of the electrostatic charge, involving the ringing of bells by electrostatic attraction and repulsion. It is used in connection with a frictional, or influence electric machine. Two bells are employed with a b.u.t.ton or clapper suspended between them. One bell is connected to one of the prime conductors, q. v., of the machine. The other insulated therefrom is connected to earth, or if an influence machine is used, to the other prime conductor. The clappers are hung by a silk thread, so as to be entirely insulated. On working the machine the bells become oppositely excited. A clapper is attracted to one, then when charged is repelled and attracted to the other, it gives up its charge and becoming charged with similar electricity to that of the bell it touches, is repelled and attracted to the other, and this action is kept up as long as the excitement continues, the bells ringing continuously.

Fig. 84. ELECTRIC CHIMES.

Chronograph, Electric.

An apparatus for indicating electrically, and thereby measuring, the lapse of time. The periods measured may be exceedingly short, such as the time a photographic shutter takes to close, the time required by a projectile to go a certain distance, and similar periods.

A drum rotated with even and known velocity may be marked by a stylus pressed upon it by the action of an electro-magnet when a key is touched, or other disturbance. Then the s.p.a.ce between two marks would give the period elapsing between the two disturbances of the circuit. As it is practically impossible to secure even rotation of a drum, it is necessary to constantly measure its rate of rotation. This is effected by causing a tuning-fork of known rate of vibration to be maintained in vibration electrically. A fine point or bristle attached to one of its arms, marks a sinuous line upon the smoked surface of the cylinder. This gives the basis for most accurately determining the smallest intervals.

Each wave drawn by the fork corresponds to a known fraction of a second.

For projectiles, the cutting of a wire opens a circuit, and the opening is recorded instead of the closing. By firing so as to cut two wires at a known distance apart the rate is obtained by the chronograph.

Synonym--Chronoscope.

119 STANDARD ELECTRICAL DICTIONARY.

Chutaux's Solution.

A solution for bichromate batteries. It is composed as follows: Water, 1,500 parts Pota.s.sium bichromate, 100 parts mercury bisulphate, 100 parts 66? sulphuric acid, 50 parts.

Circle, Galvanic or Voltaic.

A term for the voltaic circuit; obsolete.

Fig. 85. MAGIC CIRCLE.

Circle, Magic.

A form of electro-magnet. It is a thick circle of round iron and is used in connection with a magnetizing coil, as shown, to ill.u.s.trate electro-magnetic attraction.

120 STANDARD ELECTRICAL DICTIONARY.

Circuit.

A conducting path for electric currents properly forming a complete path with ends joined and including generally a generating device of some kind. Part of the conduction may be true and part electrolytic. (See Electrolytic Conduction.) The term has become extended, so that the term is often applied to any portion of a circuit conveniently considered by itself. The simplest example of a complete circuit would be a circular conductor. If rotated in the earth's field so as to cut its lines of force a current would go through it, and it would be an electric circuit. Another example is a galvanic battery with its ends connected by a wire. Here the battery generates the current which, by electrolytic conduction, goes through the battery and by true conduction through the wire. For an example of a portion of a circuit spoken of as "a circuit"

see Circuit, Astatic.

Circuit, Astatic.

A circuit so wound with reference to the direction of the currents pa.s.sing through it that the terrestrial or other lines of force have no directive effect upon it, one member counteracting the other. It may be produced by making the wire lie in two closed curves, A and B, each enclosing an equal area, one of identical shape and disposition with the other, and with the current circulating in opposite directions in each one. Thus each circuit represents a magnetizing turn of opposite polarity and counteracting each other's directive tendency exhibited in a field of force with reference to an axis a c. Another form of astatic circuit is shown in Fig. 86. The portions C, D, lying on opposite sides of the axis of rotation a c, are oppositely acted on by the earth's directive force as regards the direction of their rotation.

Figs. 86 and 87. ASTATIC CIRCUITS.

Circuit, Branch.

A circuit dividing into two or more parts in parallel with each other.

121 STANDARD ELECTRICAL DICTIONARY.

Circuit Breaker.

Any apparatus for opening and closing a circuit is thus termed, but it is generally applied to automatic apparatus. A typical circuit breaker is the hammer and anvil of the induction coil. (See Induction Coil; Anvil.) Again a pendulum connected to one terminal of a circuit may swing so as to carry a point on its lower end through a globule of mercury as it swings, which globule is connected to the other terminal.

A great many arrangements of this character have been devised.

Synonym.--Contact Breaker.

Circuit Breaker, Automatic.

A circuit breaker worked by the apparatus to which it is attached, or otherwise automatically. (See Induction Coil; Anvil; Bell, Electric.)

Circuit Breaker, File.

A coa.r.s.ely cut file, forms one terminal of an electric circuit, with a straight piece of copper or steel for the other terminal. The latter terminal drawn along the teeth makes and breaks the contact once for every tooth. The movable piece should have an insulated handle.

Circuit Breaker, Mercury.

A circuit breaker which may be identical in principle, with the automatic circuit breaker of an induction coil, but in which in place of the anvil, q. v., a mercury cup is used, into which the end of a wire dips and emerges as it is actuated by the impulses of the current. Each dip makes the contact, which is broken as the wire springs back. The mercury should be covered with alcohol to protect it from oxidation.