Selimo Romeo Bottone

“ If we immerse a strip of ordinary commercial sheet zinc in dilute acid (say sulphuric acid 1 part by measure, water 16 parts by measure [4] ) , we shall find that the zinc is immediately acted on by the acid, being rapidly corroded and dissolved, while at the same time a quantity of bubbles of gas are seen to collect around, and finally to be evolved at the surface of the fluid in contact with the plate. Accompanying this chemical action, and varying in a degree proportionate to the intensity of the action of the acid on the zinc, we find a marked development of heat and electricity. ”

“ If, however, we now connect the two plates together by means of any conductor, say a copper wire, then the strain to which the carbon plate is subjected finds its exit along the wire and the zinc plate, which is continually losing its strain under the influence of the acid, being thus at a lower potential (electrical level, strain) than the carbon, can and does actually take in and pass on the electric vibrations. It is therefore evident that no true "current" can pass unless the two elements of a battery are connected up by a conductor. ”

“ An electric bell is an arrangement of a cylindrical soft iron core, or cores, surrounded by coils of insulated copper wire. On causing a current of electricity to flow round these coils, the iron becomes, for the time being, powerfully magnetic (see § 13) . A piece of soft iron (known as the armature) , supported by a spring, faces the magnet thus produced. This armature carries at its free extremity a rod with a bob, clapper or hammer, which strikes a bell, or gong, when the armature, under the influence of the pull of the magnet, is drawn towards it. ”

“ In the first place, it must be borne in mind that a cell or battery, when at work, is continually setting up electric undulations, somewhat in the same way that an organ pipe, when actuated by a pressure of air, sets up a continuous sound wave. ”

“ As the property which zinc possesses of causing the extrication of gas (under the above circumstances) has a considerable influence on the efficiency of a battery, it is well to understand thoroughly what chemical action takes place which gives rise to this evolution of gas.
§ 18. All acids may be conveniently regarded as being built up of two essential portions, viz.: firstly, a strongly electro-negative portion, which may either be a single body, such as chlorine, iodine, bromine, etc., or a compound radical, such as cyanogen; secondly, the strongly electro-positive body hydrogen. ”

“ It is found that if a body be moved before the poles of a magnet in such a direction as to cut the lines of force, electricity is excited in that body, and also around the magnet. The ordinary magneto-electric machines of the shops are illustrations of the application of this property of magnets. They consist essentially in a horse-shoe [Pg 15] magnet, in front of which is caused to rotate, by means of appropriate gearing, or wheel and band, an iron bobbin, or pair of bobbins, coiled with wire. ”

“ Whenever possible, the wiring of a house, etc., for bell work, should be done as soon as the walls are up and the roof is on. The shortest and straightest convenient route from bell to battery, etc., should always be chosen where practicable to facilitate drawing the wire through and to avoid the loss of current which the resistance of long lengths of wire inevitably entails. The wires should be run in light zinc tubes nailed to the wall. ”

“ It is better to rivet the platinum than to solder it, as the platinum is very apt to absorb the solder, in which case it rusts quickly, and the goodness of the contact is soon spoiled, when the bell ceases to ring. To rivet the platinum piece on to the spring, as shown at Fig. 26, it is only needful to procure a short length of No. 16 platinum wire, say 1⁄8 in., then, having drilled a corresponding hole at the desired spot in the contact spring, put the platinum wire half way through the hole, and give it one or two sharp blows on an anvil, with a smooth (pened) hammer. ”

“ Unfortunately, bichromate of potash is not very soluble in water; one pint of water will not take up much more than three [Pg 47] ounces of this salt. Hence, though the solution of potassium bichromate is an excellent depolariser as long as it contains any of the salt, it soon becomes exhausted. When bichromate of potash is used in a cell along with sulphuric acid and water, sulphate of potash and chromic acid are formed, thus:—
From this we learn that before the potassium bichromate enters into action in the battery, it is resolved into chromic acid. ”

“ The Bobbins, on which the wire that serves to carry the magnetising current is to be wound, next demand our attention. They may be turned out of boxwood, ebony, or ebonite, or out of any hard wood strong enough and dense enough to allow of being turned down thin in the body, a very necessary requirement to bring the convolutions of wire as near the coil as possible without touching it. Some amateurs use the turned ends of cotton reels or spools, and glue them on to a tube of paper formed on the cores themselves. ”

“ Taking Figs. 33 A and B as our typical forms of trembling bell, the first notable modification is one by means of which the bell is made to give a single stroke only, for each contact with the battery. This form, which is known as the "single stroke bell," lends itself to those cases in which it may be required to transmit preconcerted signals; as also where it is desired to place many bells in one circuit. Fig. 34 illustrates the construction of the single stroke bell. It differs from the trembling bell in the mode in which the electro-magnet is connected up to the binding screws. ”

“ Should the battery be faulty, it will be well to renew the zincs and recharge the battery, if the porous cell be still in good condition; if not, new cells should be substituted for the old ones. Should the battery be all right, and still none of the bells ring, a break or bad contact, or short circuit in the main wires near the battery may be the cause of the mischief. If some bell rings continuously, there must be a short circuit in the push or pushes somewhere; the upper spring of one of the pushes may have got bent, or have otherwise caught in the lower spring. ”

“ When they pass along a damp wall, it is best to fix a board and loosely staple them. In no case allow more than one wire to lie under the same staple, and do not let the staples touch one another. In many cases, electric bells have been an incessant annoyance and complete failure, through driving the staples tight up to the wires, and several wires to the same staple,—this must not be done on any account. A number of wires may be twisted into a cable, and run through a short piece of gutta-percha tube, and fastened with ordinary gas hooks where it is an advantage to do so. ”

“ In order to ensure a large surface of contact for the terminal of the carbon rod or plate, it is customary to cast a leaden cap on the top thereof; and, as the porosity [Pg 35] of the graphite, or carbon, is very apt to allow the fluid in the battery to creep up to and corrode the terminal, and thus oppose resistance to the passage of electricity, the upper end of the carbon, before the lead cap is cast on, is soaked for some time in melted paraffin wax, at a temperature of 110° Centigrade: that is somewhat hotter than boiling water heat. ”

“ If the wire has been wound on the bare cores (without bobbins) , as is sometimes done, bared places in the wire may be touching the iron. This may be ascertained by connecting one pole of a bottle bichromate, or other powerful battery, with one of the wires of the electro-magnet coils, and drawing the other pole of the battery across the clean iron faces of the electro-magnet poles. If there is any leakage, sparks will appear on making and breaking contact. Nothing but unwinding and rewinding with a well covered wire can remedy these defects. ”

“ If the bells are single stroke bells, they work very well in series; but, to get trembling bells to work in series, it is best to adopt the form of bell recommended by Mr. F. C. Allsop. He says: "Perhaps the best plan is to use the form of bell shown at Fig. 82, which, as will be seen from the figure, governs its vibrations, not by breaking the circuit, but by shunting its coils. On the current flowing round the electro-magnet, the armature is attracted, and the spring makes contact with the lower screw. [Pg 164] There now exists a path of practically no resistance from end to end. ”

“ If the wire used to wind the electro-magnet be old, badly covered, or bared in several places in winding, it probably will allow the current to "short circuit," instead of traversing the whole length of the coils. If this be the case, the magnet will be very weak: the magnet of a 21⁄2-in. bell should be able to sustain easily a 1 lb. weight attached by a piece of string to a smooth piece of 1⁄2-in. square iron placed across its poles, when energized by a single pint Leclanché cell. If it will not do this, the insulation may be suspected. ”

“ On no account should the two opposite earth wires be soldered to water mains and gas mains at the same time, since it has been found that the different conditions in which these pipes find themselves is sufficient to set up a current which might seriously interfere with the working of the battery proper. Sometimes there is no means of getting a good earth except through the gas main: in this case we must be careful to get to the street side of the meter, for the red lead joints will prevent good conductivity being obtained. ”

“ A tin-plate worker may even cut his base-plate out of stout block tin, and get as good results as if the bell were made by an engineer. In some makes, the base-plate is cut or stamped out of thick sheet-iron, in the form shown by the dotted lines on Fig. 18, and when thus made, the part A is turned up at right angles to form a bracket for the magnet cores, the opposite projection is cut off, and a turned brass pillar is inserted at B to hold the contact screw, or contact breaker (§ 41) . ”

“ A wire must be led from the lower contact spring of the double contact push, to the main battery carbon wire in the shaft. A second wire is led from the upper contact stop of the double contact push to the bell, and thence to the main battery zinc wire on the shaft. Lastly, a third wire is taken from the upper contact spring of the push and connected to that particular wire in the shaft which by means of the spoonbill springs connects the particular push and indicator in the cab, destined to correspond with it. ”

“ This impairs the action, by causing the zinc to act electrically, like a copper one. Indeed, without any shaking, the liquids mix by diffusion, even when a porous pot is employed; hence a Daniell's cell is found to keep in better order if it be always allowed to send a weak current when not in use, since the current uses up the copper sulphate solution, instead of allowing it to diffuse." The use of a solution of zinc sulphate to act on the zinc rod, or plate, is always to be preferred in the Daniell cell, when long duration is of more consequence than energetic action. ”

“ Farther, it will be found that the rubber with which the ebonite or the glass rod have been excited has also acquired electrical properties, attracting the pith-ball, previously repelled by the rod. From this we may gather that when one body acting on another, either mechanically or chemically, sets up an electrical condition in one of the two bodies, a similar electrical condition, but in the opposite sense, is produced in the other: in point of fact, that it is impossible to excite any one body without exciting a corresponding but opposite state in the other. ”

“ Ammonia gas therefore slowly escapes while this battery is in action, and this corrodes all the brass work with which it comes into contact, producing a bluish green verdigris. If there be not sufficient ammonium chloride in solution, the water alone acts on the zinc: zinc oxide is produced, which renders the solution milky. Should this be the case, more sal ammoniac must be added. It is found that for every 50 grains of zinc consumed in this battery, about 82 grains of sal ammoniac and 124 grains of manganese dioxide are needed to neutralize the hydrogen set free. ”

“ It is absolutely essential that the iron be very soft and well annealed, otherwise the iron cores retain a considerable amount of magnetism when the current is not passing, which makes the bell sluggish in action, and necessitates a higher battery power to make it work (see § 14) . Two bobbins of insulated wire are fitted on the cores, and the magnet is held in its place by a transverse strip of brass or iron secured by a wood screw passing between the two bobbins. ”