ELECTRICITY, Contact Theory of, a theory which assumes that the electromotive force of a voltaic cell, and perhaps the electricity produced by friction, is due to the difference of potential assumed by two dissimilar substances when placed in contact.

ELECTRICITY, Diffusion of. Electricity diffuses itself on the surface of a conductor. This may be proved very easily, by a simple apparatus devised by Faraday. An insulated spherical conductor has two hemispherical cups carefully fitted to it, each attached to an insulating handle. The conductor and its covering are charged with electricity, the cups are then removed and the conductor is brought near an electroscope. No divergence of the leaves occurs, indicating that none of the electricity has passed into the conductor. If the conductor have a spherical shape, the electricity distributes itself equally over the surface; in other words, the density is the same on every part of the surface. We may conceive the electric fluid to surround the conductor as an ocean of uniform depth. If the conductor be a brass disc, the electricity is found in greater quantity at the edges or rim. If it be a brass cylinder with rounded ends, the density is greatest at the ends. If the conductor have the shape of a cone, the density is greatest at the apex, and the sharper the apex the greater the density. Hence the remarkable effect of a pointed body in dissipating an electric charge.

ELECTRICITY, Dissipation of. The gradual loss of electricity from a charged body surrounded by non-conductors which takes place by means of them is called dissipation of the electric charge. A charged conductor, for instance, supported on a glass pillar, slowly loses its electricity. This is due partly to the creeping of the electricity along the surface of the glass, which, even if it be free from dust and dirt, is seldom absolutely free from an invisible film of moisture; and partly to the air that surrounds the insulated conductor, the electrified body charging the particles of air with similar electricity and then repelling them, by which means a gradual loss of charge occurs. Experiments extending over a period of several years show that this dissipation of electricity does not take place in a vacuum. Coulomb made a careful investigation into the laws of dissipation, by which he was able to allow for it in cases where he could not arrange his experiments so as to be undisturbed by it. Coulomb was led by his experiments to abandon the use of glass as a support for his conductors whenever it was possible, employing instead thin stems of shellac, and sometimes suspending small electrified bodies by well-dried silk fibres. He found that the amount of loss in a given time by means of the particles of air diminishes as the charge possessed by the conductor gets weaker and weaker, the losses in successive equal intervals of time being in geometrical progression.

ELECTRICITY, Experimental Researches in, by Michael Faraday (1839-55). A monumental work in the literature of science; not merely recording the results of experiment in what Tyndall called "a career of discovery unparalleled in the history of pure experimental

a

science," but enriching the record with thoughts, and clothing it in many passages in a style worthy of exceptional recognition. In devising and executing experiments for passing beyond the limits of existing knowledge, in a field the most difficult ever attempted by research, Faraday showed a genius and achieved a success, marking him as a thinker not less than an observer of the first order. In strength and sureness of imagination, penetrating the secrets of force in nature, and putting the finger of exact demonstration upon them, he was Shakespeare of research, the story of whose work has a permanent interest. He made electricity, in one of its manifestations, explain magnetism. He showed to demonstration that chemical action is purely electrical, and that to electricity the atoms of matter owe those properties which constitute them elements in nature. In language of lofty prophetic conception he more than suggested that the physical secret of living things, the animal and the plant, is electrical. He particularly dwelt on the amount of electricity forming the charge carried by the oxygen of the air, which is the active agent in combustion and the supporter of life in both animals and plants, and only stopped short of definitely pronouncing vitality electrical. He urged very strongly as a belief, to which no test of experiment could be applied, that gravitation is by electrical agency, and that in fact the last word of discovery and demonstration in physics will show that electricity is the universal agency in nature. And among his farreaching applications of thought guided by new knowledge was his rejection of the idea of "action at a distance," in the manner of "attraction." If a body is moved, it is not by a mysterious pull, but by a push. The moving force carries it. These ideas outran the power of science to immediately understand and accept. But Maxwell, Hertz and Helmholtz have led the way after Faraday, to the extent that his electrical explanation of light is now fully accepted. Fifteen years after his death, the greatest of his successors in physics, Helmholtz of Berlin, said in a Faraday lecture in London, that the later advances in electrical science had more than confirmed Faraday's conclusions, and that English science had made a mistake in not accepting them as its point of departure for new research. See LIGHT.

ELECTRICITY, Frictional. It was an observation made by the Greek philosopher Thales, 600 years before the Christian era, that, when amber was rubbed, it acquired the property of attracting light bodies. The cause of this attractive power was assigned to a principle to which the name of "electricity" was given derived from the Greek word for amber. When a piece of wax is rubbed on the coatsleeve, an attractive power is awakened in it; it is capable of attracting small pieces of light paper or particles of sawdust. Taking a warm glass tube closed at one end, and rubbing it with silk, the same thing is manifested. It is observed also that after contact with the wax or tube, the light bodies fall away, being seemingly repelled. If a stick of sealing-wax be rubbed with flannel and then balanced on a paper loop suspended by a silk thread and the knuckle be presented to it, the wax will in like manner follow the hand.

We have, therefore, the fact that an electrified body attracts or is attracted by an unelectrified body. Another experiment of a simple character may be mentioned. Take a piece of warm brown paper or sheet of foolscap, place it upon a warm board and rub it well over with a piece of india-rubber, it clings to the board; or remove it from the board and apply it to the wall of the room, and it adheres to the wall and remains in its position till its electricity is dissipated. Observation of these phenomena led to the development of the electric machine (q.v.).

ELECTRICITY FROM HEAT. The deriving of electricity directly from the application of heat is interesting, though it has not proven of commercial value. Two different metals in contact usually show a difference of potential. This difference is most marked in the case of bismuth and antimony. When bars of these metals are soldered together at one end and the opposite ends connected by a copper wire, and a flame is applied to the point of junction a slight electric current is set up, flowing through the closed circuit thus formed. The cooling of the point of junction also sets up a current. An apparatus made on this principle is called a thermo-electric couple, and a series of such couples, arranged to work together, is called a thermopile; a still larger aggregation of thermoelectric couples arranged in rings superimposed has been styled a thermo-electric generator. With any of these contrivances the current obtained is so minute as to serve no purpose except experiment. The thermopile is valued for experimental purposes because of the great constancy obtainable with a very slight current. Iron is not a good metal to use in a thermopile, because at certain temperatures its potential coincides with nearly all other metals, so that there would be no current when that temperature was reached.

Pyroelectricity is not to be confused with thermo-electricity because of the similarity of name. It treats of the phenomena of electric polarity in minerals on being heated or cooled. The quality of pyroelectricity is best shown in tournaline, a crystal of which on being heated from about 10° to 150° C. displays positive electrification at one end and negative at the other; but on cooling the polarity is reversed and the positive and negative ends change places. Twin crystals of quartz also show the phenomena and other crystals in a lesser degree.

ELECTRICITY IN MEDICINE. ELECTROTHERAPEUTICS.

ELECTRICITY IN MINING. MINES AND MINING.

See

See

ELECTRICS and NON-ELECTRICS. The chief work of the earliest experimenters in electricity was to divide bodies into electrics, which they could excite by friction, like amber; and non-electrics, such as the metals, which they could not so excite. These names were given to the two classes by Gilbert of Colchester (1600). But Du Fay (1733–45) showed that electrics are identical with non-conductors, and non-electrics with conductors; and that the reason why nonelectrics did not exhibit excitement by friction was that the electricity was conducted away from them as fast as it was produced. The distinction was thus broken down.

ELECTRO-BIOLOGY, the science which treats of the electric currents developed in living organisms; also the department of knowledge which treats of the influence or control over the feelings, thoughts and actions of a mesmerized person. Very simple powers of observation show that the motions of a man's body are under the direction of his will. He puts forth his hand because he wills to do so; he walks through volition, even though his mind be occupied with other things; and talks or is silent as his will directs. It follows that there is some method by which the will communicates with the physical mechanism of that wonderful machine, the human body. Through anatomy we learn that the muscles do the work, and that the nerves guide the muscles, and that the nerves all proceed from or centre in the brain. Through chiropractic we learn to plot the paths of the nerves through the body, and discover when their office is interfered with. Through phrenology we learn that certain classes of nerves connect with certain portions of the brain, and thus certain brain areas are identified with certain physical, mental and moral capacities.

But the thing we cannot demonstrate-because we cannot see it is just how the will connects with a portion of the brain and sends out its order, which we know travels through the nerves to the muscles. Therefore we have to theorize as to how this is done, and the best theory appears to be the electric or magnetic theory, that that which Mesmer called "animal magnetism" is the medium of exchange. This is not meant as an endorsement of all that Mesmer said and did - far from it- but simply that the force, process or thing used and little understood by Mesmer is the same force, process or thing that translates a man's will into brain action. The problem is elucidated by a study of hypnotism and mediumistic_control. It will be remembered that mesmerism and hypnotism have been identified as based on the same natural laws, and that all authorities on the subject are in agreement that in hypnotism one person's will is replaced by another person's. The subject (or victim) of a hypnotist surrenders his will to the hypnotist, to the degree in which he is brought under the influence of hypnosis. This is why the subject obeys the commands of the hypnotist, even when told to do ridiculous and absurd things. The hypnotist has got control of the subject's "magnetism" for the time being, and he is helpless, a mere puppet or slave of his hypnotist's will. This is logical and rational, and for a fuller exposition of the subject the reader is referred to the article on HYPNOTISM. Mesmer apparently was right in his assumption that by mesmeric passes he gained control of his patient's magnetism. His theory was that there existed "a fluid universally diffused, continuous, and naturally susceptible of receiving, propagating and communicating all motor disturbances.» (Binet and Fere, 'Animal Magnetism,' p. 5.) This is exactly the sort of fluid that meets the requirements of transmitting one's will to one's brain and nerves; but to-day we do not use the word "fluid,» rather "ether" to express the medium

through which electricity, magnetism, X-rays and similar manifestations are believed to travel. Mesmer considered that the human body was charged with this magnetism much as the earth is charged with electricity, and the theory stands analysis. He called it "animal magnetism," which is here used as the most familiar term, though it might better be termed "physical magnetism.» That animals have it as well as humans is shown by the fact that animals can be hypnotized. Away back in 1646 Father Athanasius Kirchner described his hypnotizing of poultry, and later this became a fashionable pastime in France. In 1872 Czermak repeated his experiments, and also hypnotized birds, rabbits, salamanders and crabs.

Whether this animal magnetism is identical with animal electricity, or whether as is more probable it is a separate form of some higher etheric vibration than electricity, is interesting, but not all-important, and appears never to have been demonstrated. The vital fact of interest in electro-biology is that the human organism is virtually a vitalized dynamo, that gathers charge from the air breathed, and which gives off energy through the muscles under the direction of the will. Electrical engineers commonly make this comparison, being struck with the similarity of the human organism with the electric dynamo. And the fact that the human organism gets its charge of magnetism through the air breathed suggests that human magnetism is either universal in space or at least existent in both the air and water in which men and fishes live.

Another proof of the reality of this thing we call "animal magnetism" is furnished by spiritualistic or mediumistic phenomena. The "animal magnetism" is believed to be the cause of the "aura," of which every student has read, but which few have seen. Spiritualistic mediums often speak of witnessing an individual's aura, but this evidence will satisfy only those who believe in mediumship. To actually see the aura or evidence of human magnetism this experiment is suggested: Arrange a perfectly black background and place a large, strong man about five feet in front of it, at dusk or twilight. Take a position 20 to 40 feet away, and gaze steadily on the scarcely visible form of the man. When the conditions and distances are right anyone of good sight will see a faint radiance or aura emanating from and outlining the man on the black background. It is claimed that the more moral the man the brighter the aura, and that this is why the old masters painted auras about the heads of pictures of saints and especially of Jesus Christ. Another evidence of the reality of this magnetism comes from the spiritualistic mediums. They claim that the work of mediumship is extremely exhausting, and deprives them of their magnetism, and that this is why they cannot give genuine exhibitions ad libitum as visitors may demand. And many who have investigated mediumship are convinced that this is so.

The term electro-biology was coined about 1850 to describe the relationship between electricity and life. We do not know what electricity is, and we do not know what life is; we have to judge of both by their manifestations. We know little of the nature and nothing

of the origin of either, although some scientific men and some theologians are apt to be dogmatic in asserting that this or that must be or cannot be possible. But we do know that through some medium the will controls man's sensory organism and physical functions, and we choose to call this thing "animal magnetism," as Mesmer called it, and to consider it of the nature of electricity. Reasoning analogously, that as the wireless telegraph conveys a certain vibration which may be picked up by an instrument hundreds of miles away through etheric vibrations, caught by a coherer or detector, so we conclude that the will also originates vibrations, which many call thought-vibrations, and sends them through the etheric magnetism that imbues all men and animals, and perhaps all nature. But ordinarily these vibrations are picked up and responded to only by the organism of the man who sends them out, presumably because his magnetic vibrations harmonize with his physical body. It is also logical to reason that this sort of magnetism exists everywhere, as we suppose electricity pervades the universe, and that the phenomena of telepathy or thoughttransference, and mind-reading, are explainable through harmonic vibrations of the ether which this magnetism permeates and pervades. Clairvoyage and clairaudience likely are closely related, so that in solving the problem of physical magnetism probably these will also se solved.

It is stated in The Great Psychological Crime' (p. 178) that "animal magnetism is an important factor in the development of mediumship," and that "the room in which the sittings are held must become thoroughly magnetized with the animal magnetism of the controlling intelligences." The reader who cares to pursue the subject further should consult this book. CHARLES H. COCHRANE. ELECTRO-BRONZE. See ELECTROPLAT

ING.

ELECTROCHEMICAL EQUIVALENTS. The general principles of electrochemistry (q.v.) and especially Faraday's laws (q.v.) have shown us a definite quantitative relation between the amount of electricity passing in a given electrolysis, and the amount of decomposition resulting. According to Faraday's laws, the amount of any given element which will be deposited by a given amount of current is directly proportional to the amount of current passing, and to the chemically equivalent weight of the element in question. Quantitatively, it requires 96,500 coulombs of electricity (ampere-seconds) to deposit a chemically equivalent weight of any substance; or, to put it in a more practical way, it requires 96,500 coulombs to make a unit change of valence of a gramatom of any substance. From this numerical relation one can then calculate the weight of any element that will be deposited by a unit amount of current in a unit time. This is called the Electrochemical Equivalent of the element. For scientific purposes it is usually stated in grams per coulomb or per amoere-hour; for commercial use larger units are convenient, such as kilograms or pounds per ampere-day, or per 1,000 ampere-hours.

These values are taken from Electrochemical Equivalents' by Hering and Getman (New York 1917).

G. A. ROUSH, Assistant Secretary, American Electrochemical Society.

ELECTROCHEMICAL INDUSTRIES. Electrochemistry may be defined as that branch of chemistry relating to the carrying out of chemical reactions by the means of or with the assistance of electricity. The word electrochemical as here used includes the processes of electrometallurgy, the production and treatment of metals by means of electricity, there being no generic term covering both subjects.

The production or furtherance of chemical action by means of electrical energy may be secured in three ways: (1) By electrolysis— the action of an electric current upon a chemical compound in solution or in a fused condition; (2) by electrothermal action - the production of chemical changes by electrically generated heat; (3) by the discharge of electricity through gases.

The largest employment of electrolysis is in the production and refinement of metals, particularly aluminum and copper; but it is also used extensively in the preparation of a large number of chemical compounds of widely varying character.

In most cases a substance obtained by electrolysis may be prepared also by a strictly chemical process. The choice of methods then becomes simply one of cost. An example in point is the manufacture of metallic sodium: originally discovered by the electrolysis of caustic soda, it was for many years made commercially by the reduction of sodium carbonate with carbon, or of caustic soda by a mixture of iron and carbon; more recently the electrolytic process has replaced the chemical methods, because it is cheaper. In other cases certain products of electrochemical action have not yet been made by any other process.

A great saving of heat is found in most electrothermal processes, due to the fact that the electrically generated heat is applied inside the container, where it is effectively employed, no heat being wasted in heating the contents through the walls of the container, as in combustion processes. But even when produced by the cheapest water power, electric heat costs several times more than heat produced by the combustion of coal, so that where large quantities of heat are needed at only moderate temperatures, the combustion processes are usually cheaper.

We shall here consider the chief electrochemical industries that have thus far attained commercial importance.

Copper. The process of refining copper electrolytically consists in the transfer of copper from the anode to the cathode, by the selective action of the electric current, and in leaving the impurities behind dissolved in the electrolyte, or in the form of slime or sediment. The material. at present subjected to profitable electrolyte refining is crude copper containing from 96 to 98 per cent pure copper, and varying amounts of silver, gold, platinum, palladium, nickel, iron, arsenic, antimony, sulphur, etc. This crude copper is obtained from various copper ores by smelting and is cast in copper molds into anode plates, which are about three feet square and one to two inches thick, weighing 250 to 500 pounds. The cathode plates are of electrolytically refined copper, practically the same in length and width as the anodes, but only 1/32 to 1/16 inch thick. The electrolyte, or bath, in which the plates are suspended, is a solution of copper sulphate just short of saturation, with enough sulphuric acid to prevent the separation of hydrated cupric oxide, but not enough to cause hydrogen instead of copper to be separated at the cathode; the proportions are about 3-4 per cent of copper as sulphate and 10-13 per cent of free sulphuric acid. When silver is present in the anode a little salt or hydrochloric acid is added to the electrolyte. The bath is kept at a temperature of about 40-60° C. (100-140° F.). The containing tanks are of wood, usually lined with sheet lead or carefully coated with a pitch compound, and of such dimensions that a distance of from 1.5 to 2 inches exists between the faces of the plates. In some cases the plates are arranged in series and in others in parallel or multiple. In the series system the anodes,

which are much smaller than in the multiple system, are suspended in the electrolyte from one-half to three-fourths of an inch apart, and only the end ones in the series are connected with the poles of the generator. With this arrangement the copper dissolved from the inner face of the first anode is deposited on the nearer face of the second plate; the farther face of the second plate is dissolved and deposited on the nearer face of the third plate and so on throughout the series. When the anodes are nearly exhausted the pure copper deposits are removed from the tank and the undissolved remnants of anode stripped from the back of the cathodes.

The series arrangement has the advantage of requiring electrical connections to be made at the first and last plates only, whereas the parallel system requires a connection at every plate; but in the series system the leakage of current due to the short-circuiting action of the sediment and sides of the tank is from 10 to 20 per cent, so that the parallel system is more generally used. The connections between the various plates and the circuit in the parallel systems are made by copper rods, which are run at two different levels along the edges of the tanks, one bar for each set of plates. In some instances these rods are of the inverted V shape, so that the edges will cut through any corrosion which may happen to form at the points of contact. The vats are arranged, with respect to each other, so that each is accessible from all sides and free circulation of the electrolyte is possible. This circulation is sometimes obtained by blowing a stream of air through the electrolyte, but more frequently by arranging the vats in steps, and piping so that the electrolyte may pass from the top of one vat to the bottom of the next, by the action of gravity. This maintains a uniform density of electrolyte, which is necessary for the proper formation of the deposit. The electromotive force required is from 0.2 to 0.4 volt per tank, with a current density of 15 to 20 amperes per square foot of cathode plate surface. The individual vats are connected in series so that the total voltage may be approximately the same as that which the generator furnishes, being usually 110 volts. One ampere of current deposits on the cathode only about one ounce of refined copper in 24 hours, and the current density must be kept below 40 amperes per square foot to avoid mushrooming and consequent short-circuiting. In practice from 400 to 500 ampere-hours are required per pound of copper deposited, the theoretical amount according to Faraday's law being only 386.2 ampere-hours. The loss varies from 4 to 20 per cent according to the system employed.

The main product of refining is commercial cathodes, which are sometimes shipped to consumers, but more frequently cast into wire-bars, ingots, cakes or slabs of standard dimensions and weight. They usually assay from 99.86 to 99.94 per cent pure copper. The yield in commercial cathodes is from 97 to 99 per cent of the anodes treated, excluding the anode scrap which varies in weight from 7 to 15 per cent of the original anode in parallel plants, but this scrap is not a loss as it is collected and recast into anode plates. Besides electrolytic copper most plants secure gold, silver, platinum

and palladium from the slimes, and sometimes selenium, tellurium and other rarer metals. Nickel salts are usually recovered from the solutions.

There are in the United States 10 electrolytic copper refineries with a total capacity of 2,780,000,000 pounds per year; one refinery in Canada with a capacity of 14,000,000 pounds per year. The actual production in 1917 was about 2,300,000,000 pounds, representing approximately 74 per cent of the entire world's production of copper for the year. Or, deducting from the total production the amount that does not require refining, about 275,000,000 pounds from Michigan, the United States production amounts to over 81 per cent of the total production of refined copper. The other 19 per cent is produced in a number of plants of comparatively small capacity in England, Wales and Continental Europe.

Aluminum.- Practically the whole output of this metal for the entire world is now produced electrolytically. The only process used on a large scale is that invented independently in 1886 by Charles M. Hall in the United States and by Paul L. T. Héroult in France. This process consists in electrolyzing alumina dissolved in a fused bath of cryolite. The alumina is obtained from the mineral bauxite which occurs abundantly in Arkansas, Georgia, Alabama and Tennessee. The natural material, being a hydrated alumina containing silica, iron and titanium, must be treated in order to drive off the water and eliminate the impurities. This is accomplished by a chemical process. In practice it requires about two pounds of alumina for each pound of aluminum produced. The flux or bath in which the alumina is dissolved consists of cryolite, a natural_double fluoride of aluminum and sodium (AlF6NaF) found in Greenland. This is melted in a large carbonlined, sheet-iron tank which constitutes the negative electrode, a group of suspended carbon rods forming the positive electrode. A current of several thousand amperes at six to seven volts is used. Only a portion of this voltage is required to decompose the alumina, the balance amounting to about four to five volts represents the heat required to keep the bath melted. The passage of the current causes the aluminum to deposit on the bottom of the tank as a fused metal, whence it is drawn off periodically. The oxygen set free combines with the carbon of the positive electrodes and passes off as carbonic oxide. The reaction is Al2O2+3C= 2A1+3CO. About one pound of carbon is consumed for one pound of aluminum produced. An excess of alumina is kept floating on the bath so that it is saturated at all times. According to Faraday's law the weight of aluminum deposited by 1,000 amperes is 0.743 pound per hour. The actual yield of metal by the Hall process is about 85 per cent of this theoretical amount. The metal when drawn from the tanks is cast into rough ingots which are afterward remelted and converted into commercial shapes, such as sheets, rods, wires, etc. The United States in 1917 produced about 180,000,000 pounds of aluminum, which was about two-thirds the total production of the world. Before the European War the share of the United States in the total production was under 50 per cent.