Electric fluid

“ Before entering into the description of the electrotype, we must say a few words on the subject of electricity to the less informed of our readers. The electric fluid, as it is called, may be produced in various ways: the most ordinary is by the friction of glass against silk, as exemplified in the electrical machine, which is familiar to almost every one. But galvanic and voltaic electricity is differently produced. ”

“ Whatever hindrances might impede the progress of the ancients in other branches of knowledge, from the abstruse nature of the subject, or the want of necessary helps, it may rather excite our wonder, that the effects of electricity should remain so long unobserved. The electric fluid is no local or occasional agent; it is coeval with the world; its presence pervades every substance; it is the principal cause of the grandest scenes in nature, and its operations can hardly fail to show themselves wherever bodies are concerned. ”

“ But this supply is immediately procured from the surrounding atmosphere. The quantity sent off is instantaneously returned from the air, and a vibratory motion or struggle between the air and electric fluid, immediately takes place. The positive electricity therefore consists in a vibratory motion in the air and electric fluid; and the force of the vibration is directed outwards from the electrified body. In bodies negatively electrified, the fluid contained in the neighbouring atmosphere is directed towards the body so electrified. ”

“ The applications of the theory of electricity which I have principally considered above, are those which belong to conductors, in which the electric fluid is perfectly moveable, and can take that distribution which the forces require. In non-conducting or electric bodies, the conditions to which the fluid is subject are less easy to determine; but by supposing that the fluid moves with great difficulty among the particles of such bodies,—that nevertheless it may be dislodged and accumulated in parts of the surface of such bodies, by friction and other modes of excitement ”

“ In fact the electric fluid is much more amenable to experiment than an ordinary gas, and the details of its structure are more easily determined.
Negative electricity (i. e., the electric fluid) has mass; a body negatively electrified has a greater mass than the same body in the neutral state; positive electrification, on the other hand, since it involves the absence of corpuscles, is accompanied by a diminution in mass. ”

“ An electrified body is supposed to have a charge of some imponderable fluid “electricity.” Particles of electricity repel each other according to a certain law, and the fluid distributes itself in equilibrium over the surface of any charged conductor in accordance with this law. There are on this theory two opposite kinds of electric fluid, positive and negative, two charges of the same kind repel, two charges of opposite kinds attract; the repulsion or159 attraction is proportional to the product of the charges, and inversely proportional to the square of the distance between them. ”

“ At present, it is safer to speak of electricity as a state or condition of matter. If it were not that some very eminent electricians (and one especially whose eminence as a practical electrician is very great) are said to believe still that there is such a thing as an electric fluid, we should have simply asserted that in the present position of scientific research, with the known velocity at which the so-called electric current flows, and the known relations between [Pg 293] electricity, heat, and light, the theory of an electric fluid is altogether untenable. ”

“ Some new facts, lately discovered, seem to shew that the immediate cause which excites the electric fluid, and puts it in motion, whether it be an attraction or a repulsive power, is to be ascribed much rather to the mutual contact of two different metals, than to their contact with moist conductors. ”

“ Cavallo, proves that the electric matter passes through the substance of the metal, and not over the surface. A wire, adds he, continued through a vacuum is also a convincing proof of this assertion.
123VI. “Positive electricity is an accumulation, or too great a quantity of the electric matter contained in a body; and negative electricity is when there is too little.” This position, like the fourth, must be considered as hypothetical—the peculiar nature of the electric fluid not admitting of experiments to prove, or to disprove it. ”

“ This equal and uniform distribution of the two fluids is called the natural state; when this state is disturbed in any body, the body is said to be electrified, and the various phenomena of electricity begin to take place.
"Material bodies do not all behave in the same way with respect to the electric fluid: some, such as the metals, do not appear to exert any influence on it, but permit it to move about freely in their substance: for this reason they are called conductors. ”

“ If two bodies be both of them over-charged, the electric atmospheres repel one another, and both the bodies recede from each other, to places where the fluid is less dense.—For as there is supposed to be a mutual attraction between all bodies and the electric matter, such bodies as are electrified must go along with their atmospheres. If both bodies are exhausted of their natural share of this fluid, they are both attracted by the denser fluid, existing either in the atmosphere contiguous to them, or in other neighbouring bodies ”

“ Another mode of explanation is given by those who maintain, in opposition to Franklin, that positive and negative electricity are either two distinct fluids, or else vibrations of the same fluid—the positive electricity always rushing out of a body, and the negative always rushing in. Those who maintain this hypothesis endeavour to support it by the easy solution which they affirm it gives to the phenomena of electric attraction and repulsion. ”

“ Those which readily exhibit electrical phenomena by heating and cooling.—Of these, the tourmaline [9] is the principal.
The best method of disturbing the electric fluid, that is of making it pass from one body to another, is friction. This may be done either by rubbing one electric with another, or with a conductor; but the electricity is generally stronger in the latter case. Other methods for causing electrics to shew electric appearances, are, 6melting, or pouring a melted electric on another substance, heating and cooling, evaporating or effervescing. ”

“ When, for instance, a positively electrified body was found to induce upon another insulated conductor a charge of negative electricity on the side nearest to it, and a charge of positive electricity on the side farthest from it, this was explained by saying that the particles of each of the two electric fluids repelled one another but attracted those of the positive fluid. Hence the operation of the positive charge upon the neutral fluid was to draw towards the positive the negative constituent of the neutral charge and repel to the distant parts of the conductor the positive constituent. ”

“ Others, on the contrary—very dry air, for example—oppose the passage of the electric fluid in their interior, so that they can prevent the fluid accumulated in conductors from being dissipated throughout space. ”

“ According, then, to the two-fluid theory, the "natural fluid" contained in all matter can be decomposed, under the influence of an electric field, into equal quantities of vitreous and resinous electricity, which, if the matter be conducting, can then fly to the surface of the body. ”

“ It will often happen that the electrodes used may be of such a nature as, with the fluid in which they are immersed, to produce an electric current, either according with or opposing that of the voltaic arrangement used, and in this way, or by direct chemical action, may sadly disturb the results. Still, in the midst of all these confusing effects, the electric current, which actually passes in any direction through the body suffering decomposition, will produce its own definite electrolytic action. ”

“ They become charged by chemical action, and not by friction. The zinc is gradually dissolved, and it is this chemical burning of the zinc that furnishes energy for the electric current in the simple cell. The electrification, or charge, on the plates tends to flow from the place of higher to the place of lower potential, just as water tends to flow down hill. If a wire be joined to the two metals, a constant current of electricity will flow through it, because the acid continues to act upon the plates. The simple cell is a single-fluid cell, as but one liquid is used in its construction. ”

“ In using compressed air or water for the transmission of power, the loss can not be taken at less than 50 per cent, and as it depends upon fluid resistance it increases with distance more rapidly than in the case of electricity. Taking the loss of effect in all cases as 50 per cent, electric transmission presents the advantage that an insulated wire does the work of a pipe capable of withstanding high internal pressure, which latter must be more costly to put down and to maintain. ”

“ We shall show later that the charges and masses of the ions can be determined, and that the gaseous ions are not identical with those met with in the electrolysis of solutions.
One very characteristic property of conduction of electricity through a gas is the relation between the current through the gas and the electric force which gave rise to it. This relation is not in general that expressed by Ohm’s law, which always, as far as our present knowledge extends, expresses the relation for conduction through metals and electrolytes. ”

“ The analogy of gaseous conduction to electrolysis was applied by W. Giese, [62] of Berlin, in 1882, in order to explain the conductivity of the hot gases of flames. "It is assumed," he wrote, "that in electrolytes, even before the application of an external electromotive force, there are present atoms or atomic groups—the ions, as they are called—which originate when the molecules dissociate; by these the passage of electricity through the liquid is effected, for they are set in motion by the electric field and carry their charges with them. ”

“ When now we close the circuit, as before, a brisk effervescence takes place. Bubbles of gas rapidly form on the platinum wires and break away, rising through the liquid. Twice as many form on the negative wire as on the positive one. As these gases rise to the top of the bottle an equal volume of the water drips out through the small hole in the cork.
Fig. 153
Two amperes of electricity will liberate two fluid ounces of hydrogen at the negative pole and one [266] fluid ounce of oxygen at the positive pole, in five minutes. ”

“ It is the property of all kinds of electrics, when they are rubbed by bodies different from themselves, to attract light substances of all kinds, to exhibit an appearance of light, attended with a particular sound, on the approach of any conductor; and if the nostrils are presented, they are affected with a smell like that of phosphorus. This attraction is most easily explained by supposing that electricity is produced by a fluid exceedingly elastic, or repulsive of itself, and attracted by all other substances. ”

“ Electrolysis. It has been seen that in the voltaic cell electricity is generated by chemical action. Sulphuric acid acts upon zinc and dissolves it in the cell, hydrogen is produced, etc. When this process is reversed, that is, when the electric current is passed through some solutions, they are decomposed, or broken up into their constituents. This process is called electrolysis, and the compound decomposed is the electrolyte. (See "Study," § 369, etc., with experiments.) ”

“ Thus, for example, if such gas be blown through narrow tubes, it will be positively electrified when it comes out, for since the negative ions diffuse more rapidly than the positive, the gas in its passage through the tubes will lose by diffusion more negative than positive ions and hence will emerge positively electrified. ”

“ If at a certain place the velocity receives a sudden check by the corpuscles becoming loaded with a molecule, the density of the negative electricity will increase at this place with great rapidity, and here there will be a great accumulation of negative electricity, as at the bright head on the cathode side of a striation. Now this accumulation of negative electricity will produce a large electric force on the anode side; this will drive corpuscles forward with great velocity and ionize the gas. ”

“ Electric currents passing through the human body expend their energy partly in heat and partly in electrolysis. So simple and harmless a thing as common salt would become a virulent poison if it could be electrolized in the body into its elements sodium and chlorine.
Let us make use of an electric current to decompose water into its elements, hydrogen and oxygen. I have a three-ounce wide-mouthed bottle (Fig. 153) and through its cork I pass two short pieces of No. 24 platinum wire by pushing a stout needle through first. ”

“ If we eliminate the polarization at the electrodes, it can be shown that an electrolyte possesses a definite electric resistance and therefore a definite conductivity. The conductivity gives us the amount of electricity conveyed per second under a definite electromotive force. On the view of the process of conduction described above, the amount of electricity conveyed per second is measured by the product of the number of ions, known from the concentration of the solution, the charge carried by each of them, and the velocity with which, on the average, they move through the liquid. ”