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silver, and in the manufacture of phosphorus, potassium chlorate and bleach, already pressing very heavily on the older non-electrical systems, is every See also:

YEAR

year extending. The convenience also with which the See also:

ENERGY (from the Gr. ivipyela; iv, in, ipyov, work)

energy of waterfalls can be converted into electric energy has led to the introduction of chemical See also:

INDUSTRIES

industries into countries and districts where, owing to the See also:

ABSENCE (Lat. absentia)

absence of See also:

COAL

coal, they were previously unknown. See also:

Norway and See also:

SWITZERLAND

Switzerland have become important producers of chemicals, and See also:

PASTORAL (from Lat. pastor, a shepherd)

pastoral districts such as those in which See also:

Niagara or Foyers are situated manufacturing centres. In this way the development of the electrochemical See also:

INDUSTRY (Lat. industria, from indu-, a form of the pre, position in, and either stare, to stand, or struere, to pile up)

industry is in a marked degree altering the See also:

DISTRIBUTION (Lat. distribuere, to deal out)

distribution of See also:

trade throughout the See also:

WORLD

world. Electrolytic Refining of Metals.—The principle usually followed in the electrolytic refining of metals is to See also:

CAST (from the verb meaning " to throw "; the word is Scand. in origin, cf. Dan. kaste, and Swed. kasta; " cast " in Middle Eng. took the place of the A.S. weor pan, cf. Ger. werf en)

cast the impure See also:

metal into plates, which are exposed as anodes in a suitable solvent, commonly a See also:

salt of the metal under treatment. On passing a current of electricity, of which the See also:

VOLUME

volume and pressure are adjusted to the conditions of the electrolyte and electrodes, the anode slowly dissolves, leaving the insoluble impurities in the See also:

FORM (Lat. forma)

form of a sponge, if the proportion be considerable, but otherwise as a mud or slime which becomes detached from the anode See also:

SURFACE

surface and must be prevented from coming into contact with the See also:

CATHODE

cathode. The metal to be refined passing into See also:

SOLUTION (from Lat. solvere, to loosen, dissolve)

solution is concurrently deposited at the cathode. Soluble impurities which are more electro-negative than the metal under treatment must, if present, be removed by a preliminary See also:

PROCESS

process, and the voltage and other conditions must be so selected that none of the more electro-See also:

POSITIVE (or PORTABLE) ORGAN

positive metals are co-deposited with the metal to be refined. From these and other considerations it is obvious that (I) the electrolyte must be such as will freely dissolve the metal to be refined; (2) the electrolyte must be able to dissolve the See also:

major portion of the anode, otherwise the See also:

mass of insoluble See also:

MATTER

matter on the See also:

OUTER

outer layer will prevent See also:

ACCESS (Lat. accessus)

access of electrolyte to the core, which will thus See also:

ESCAPE (in mid. Eng. eschape or escape, from the O. Fr. eschapper, modern echapper, and escaper, low Lat. escapium, from ex, out of, and cappa, cape, cloak; cf. for the sense development the Gr. iichueoOat, literally to put off one's clothes, hence to sli

escape refining; (3) the electrolyte should, if possible, be incapable of dissolving metals more electro-negative than that to be refined; (4) the proportion of soluble electro-positive impurities must not be excessive, or these substances will accumulate too rapidly in the solution and necessitate its frequent See also:

PURIFICATION

purification; (5) the current See also:

DENSITY (Lat. densus, thick)

density must be so adjusted to the strength of the solution and to other conditions that no relatively electro-positive metal is deposited, and that the cathode See also:

DEPOSIT (Lat. depositurn, from deponere, to lay down, to put in the care of)

deposit is physically suitable for subsequent treatment; (6) the current density should be as high as is consistent with the See also:

PRODUCTION (Lat. productionem, from producere, to pro-duce)

production of a pure and See also:

sound deposie, without undue expense of voltage, so that the operation may be rapid and the " turnover " large; (7) the electrolyte should be as See also:

GOOD, JOHN MASON (1764-1827)

good a conductor of electricity as possible, and should not, ordinarily, be altered chemically by exposure to See also:

air; and (8) the use of porous partitions should be avoided, as they increase the resistance and usually require frequent renewal.

For details of the See also:

PRACTICAL

practical methods see See also:

GOLD; SILVER; COPPER and headings for other metals. Electrolytic Manufacture of Chemical Products.—When an aqueous solution of the salt of an See also:

ALKALI

alkali metal is electrolysed, the metal reacts with the See also:

WATER

water, as is well known, forming See also:

CAUSTIC (Gr. rcavvraubs, burning)

caustic alkali, which dissolves in the solution, and See also:

HYDROGEN [symbol H, atomic weight x-oo8 (0=16)]

hydrogen, which comes off as a See also:

gas. So See also:

early as 185 a patent was taken out by See also:

Cooke for the production of caustic alkali without the use of a See also:

SEPARATE

separate current, by immersing See also:

IRON [symbol Fe, atomic weight 55.85 (0=16)]

iron and copper plates on opposite sides of a porous (See also:

BISCUIT (pronounced according to the old spelling " bisket," a Fr. form from Lat. bis, twice, and coctum, cooked, in reference to the original method of preparation; cf. Ital. biscotto, Sp. bizcocho, &c.)

biscuit-See also:

WARE

ware) See also:

PARTITION

partition in a suitable See also:

CELL (from Lat. cella, probably from an Indo-European kal —seen in Lat. celare, to hide; another suggestion connects the word with Lat. cera, wax, taking the original meaning to refer to the honeycomb)

cell, containing a solution of the salt to be electrolysed, at 21°-65° C. (70°-150° F.). The solution of the iron anode was intended to afford the necessary energy. In the same year another patent was granted to C. See also:

WATT, JAMES (1736-1819)

Watt for a similar process, involving the employment of an externally generated current. When an alkaline chloride, say sodium chloride, is electrolysed with one electrode immersed in a porous cell, while caustic soda is formed at the cathode, See also:

CHLORINE (symbol Cl, atomic weight 35`46 (0=16)

chlorine is deposited at the anode. If the latter be insoluble, the gas diffuses into the solution and, when this becomes saturated, escapes into the air. If, however, no porous See also:

DIVISION (from Lat. dividere, to break up into parts, separate)

division be used to prevent the intermingling by See also:

DIFFUSION (from the Lat. diffundere; dis-, asunder, and fundere, to pour out)

diffusion of the anode and cathode solutions, a complicated set of subsidiary reactions takes See also:

PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place. The chlorine reacts with the caustic soda, forming sodium hypochlorite, and this in turn, with an excess of chlorine and at higher temperatures, becomes for the most See also:

PART

part converted into chlorate, whilst any simultaneous electrolysis of a hydroxide or water and a chloride (so that hydroxyl and chlorine are simultaneously liberated at the anode) also produces See also:

OXYGEN (symbol 0, atomic weight 16)

oxygen-chlorine compounds See also:

DIRECT

direct. At the same See also:

time, the diffusion of these compounds into contact with the cathode leads to a partial reduction to chloride, by the removal of combined oxygen by the instrumentality of the hydrogen there evolved.

In proportion as the See also:

ORIGINAL

original chloride is thus reproduced, the efficiency of the process is of course diminished. It is obvious that, with suitable methods and apparatus, the electrolysis of alkaline chlorides may be made to yield chlorine, hypochlorites (See also:

BLEACHING

bleaching liquors), See also:

CHLORATES

chlorates or caustic alkali, but that See also:

GREAT

great care must be exercised if any of these products is to be obtained pure and with See also:

ECONOMY

economy. Many See also:

PATENTS

patents have been taken out in this See also:

BRANCH (from the Fr. branche, late Lat. branca, an animal's paw)

branch of electrochemistry, but it is to be remarked that that granted to C. Watt traversed the whole of the ground. In his process a current was passed through a tank divided into two or three cells by porous partitions, hoods and tubes were arranged to carry off chlorine and hydrogen respectively, and the whole was heated to 1200 F. by a See also:

steam jacket when caustic alkali was being made. Hypochlorites were made, at See also:

ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

ordinary temperatures, and chlorates at higher temperatures, in a cell without a partition in which the cathode was placed horizontally immediately above the anode, to favour the mixing of the ascending chlorine with the descending caustic solution. The relation between the See also:

composition of the electrolyte and the various conditions of current-density, temperature and the like has been studied by F. Oettel (Zeilschrift f. Elektrochem., 1894, vol. i. pp. 354 and 474) in connexion with the production of hypochlorites and chlorates in tanks without diaphragms, by C. Haussermann and W. Naschold (Chemiker Zeitung, 1894, vol. xviii. p.

857) for their production in cells with porous diaphragms, and by F. Haber and S. Grinberg (Zeilschrift f. anorgan. Chem., 1898, vol. xvi. pp. 198, 329, 438) in connexion with the electrolysis of hydrochloric See also:

ACID (from the Lat. root ac-, sharp; acere, to be sour)

acid. Oettel, using a 2o% solution of potassium chloride, obtained the best yield of hypochlorite with a high current-density, but as soon as It % of bleaching chlorine (as hypochlorite) was present, the formation of chlorate commenced. The yield was at best very See also:

low as compared with that theoretically possible. The best yield of chlorate was obtained when from i to 4% of caustic potash was present. With high current-density, See also:

HEATING

heating the solution tended to increase the proportion of chlorate to hypochlorite, but as the proportion of water decomposed is then higher. the amount of chlorine produced must be less and the See also:

TOTAL

total chlorine efficiency See also:

LOWER

lower. He also traced a connexion between alkalinity, temperature and current-density, and showed that these conditions should be mutually adjusted. With a current-density of 13o to 14o amperes per sq. ft., at 3 volts, passing between See also:

PLATINUM [symbol Pt, atomic weight 145.0 (0=16)]

platinum electrodes, he attained to a current-efficiency of 52 %, and each (See also:

BRITISH

British) electrical See also:

HORSE (a word common to Teutonic languages in such forms as hors, hros, ros; cf. the Ger. ross)

horse-See also:

POWER [WILLIAM GRATTAN] TYRONE (1797-1841)

power See also:

HOUR

hour was See also:

EQUIVALENT

equivalent to a production of 1378.5 grains of potassium chlorate. In other words, each See also:

pound of chlorate would require an See also:

EXPENDITURE

expenditure of nearly 5.1 e.h.p. See also:

HOURS, CANONICAL

hours.

One of the earliest of the more See also:

MODERN

modern processes was that of E. Hermite, which consisted in the production of bleach-liquors by the electrolysis (according to the 1st edition of the 1884 patent) of magnesium or calcium chloride between platinum anodes carried in wooden frames, and See also:

ZINC

zinc cathodes. The solution, containing hypochloritesand chlorates, was then applied to the bleaching of See also:

LINEN

linen, See also:

paper-pulp or the like, the solution being used over and over again. Many modifications have been patented by Hermite, that of 1895 specifying the use of platinum See also:

GAUZE

gauze anodes, held in ebonite or other frames. Rotating zinc cathodes were used, with scrapers to prevent the See also:

ACCUMULATION (from Lat. accumulare, to heap up)

accumulation of a layer of insoluble magnesium compounds, which would otherwise increase the electrical resistance beyond reasonable limits. The same inventor has patented the application of electrolysed chlorides to the purification of See also:

STARCH

starch by the oxidation of less See also:

STABLE

stable organic bodies, to the bleaching of See also:

OILS (adopted from the Fr. oile, mod. huile, Lat. oleum, olive oil)

oils, and to the purification of coal gas, spirit and other substances. His See also:

SYSTEM

system for the disinfection of sewage and similar matter by the electrolysis of chlorides, or of See also:

sea-water, has been tried, but for the most part abandoned on the See also:

SCORE (O.E. scor, from sceran, to cut, notch, cf. " shear ")

score of expense. Reference may be m.; de to papers written in the early days of the process by C. F. See also:

CROSS

Cross and E. J. Bevan (Journ.

See also:

Soc. Chem. Industry, 1887, vol. vi. p. 170, and 1888, vol. vii. p. 292), and to later papers by P. Schoop (Zeilschrift f. Elektrochem., 1895, vol. ii. pp. 68, 88, 107, 209, 289). E. Kellner, who in 1886 patented the use of cathode (caustic soda) and anode (chlorine) liquors in the manufacture of See also:

CELLULOSE

cellulose from See also:

wood-fibre, and has since evolved many similar processes, has produced an apparatus that has been largely used. It consists of a stoneware tank with a thin See also:

SHEET

sheet of platinum-See also:

IRIDIUM (symbol Ir.; atomic weight 193.1)

iridium alloy at either end forming the See also:

PRIMARY

primary electrodes, and between them a number of See also:

glass plates reaching nearly to the bottom, each having a platinum gauze sheet on either See also:

side; the two sheets belonging to each See also:

PLATE

plate are in metallic connexion, but insulated from all the others, and form intermediary or bi-polar electrodes. A 10-12 % solution of sodium chloride is caused to flow upwards through the apparatus and to overflow into troughs, by which it is conveyed (if necessary through a cooling apparatus) back to the circulating See also:

PUMP

pump.

Such a plant has been reported as giving 0.229 See also:

GALLON

gallon of a liquor containing 1 % of available chlorine per kilowatt hour, or 0.171 gallon per e.h.p. hour. Kellner has also patented a " bleaching-See also:

block," as he terms it, consisting of a See also:

FRAME

frame carrying parallel plates similar in principle to those last described. The block is immersed in the solution to be bleached, and may be lifted in or out as required. O. Knofler and Gebauer have also a system of bi-polar electrodes, mounted in a frame in See also:

APPEARANCE (from Lat. apparere, to appear)

appearance resembling a See also:

FILTER (a word common in various forms to most European languages, adapted from the medieval Lat. fi-ltrum, felt, a material used as a filtering agent)

filter-See also:

PRESS (through Fr. presse from Lat. pressare, frequentative of premere, to crush, squeeze, press)

press. Other Electrochemical Processes.—It is obvious that electrolytic See also:

IODINE (symbol I, atomic weight '26.92)

iodine and See also:

BROMINE (symbol Br, atomic weight 79-96)

bromine, and oxygen compounds of these elements, may be produced by methods similar to those applied to chlorides (see ALKALI MANUFACTURE and CHLORATES), and Kellner and others have patented processes with this end in view. Hydrogen and oxygen may also be produced electrolytically as gases, and their respective reducing and oxidizing See also:

POWERS, HIRAM (1805-1873)

powers at the moment of deposition on the electrode are frequently used in the laboratory, and to some extent industrially, chiefly in the See also:

field of organic See also:

chemistry. Similarly, the formation of organic halogen products may be effected by electrolytic chlorine, as, for example, in the production of See also:

CHLORAL

chloral by the See also:

GRADUAL (Med. Lat. gradualis, of or belonging to steps or degrees; gradus, step)

gradual introduction of See also:

ALCOHOL

alcohol into an anode cell in which the electrolyte is a strong solution of potassium chloride. Again, anode reactions, such as are observed in the electrolysis of the fatty acids, may be utilized, as, for example, when the See also:

RADICAL (Lat. radix, a root)

radical CH3CO2—deposited at the anode in the electrolysis of acetic acid—is dissociated, two of the See also:

groups react to give one See also:

MOLECULE (from mod. Lat. molecula, the diminutive of moles, a mass)

molecule of ethane, See also:

C2H6

C2H6, and two of See also:

CARBON (symbol C, atomic weight 12)

carbon dioxide. This, which has See also:

long been recognized as a class-reaction, is obviously capable of endless variation. Many electrolytic methods have been proposed for the purification of See also:

SUGAR

sugar; in some of them soluble anodes are used for a few minutes in weak alkaline solutions, so that the caustic alkali from the cathode reaction may precipitate chemically the hydroxide of the anode metal dissolved in the liquid, the precipitate carrying with it mechanically some of the impurities present, and thus clarifying the solution. In others the current is applied for a longer time to the original sugar-solution with insoluble (e.g. carbon) anodes.

F. See also:

Peters has found that with these methods the best results are obtained when See also:

OZONE

ozone is employed in addition to electrolytic oxygen. Use has been made of electrolysis in tanning operations, the current being passed through the tan-liquors containing the hides. The current, by endosmosis, favours the passage of the solution into the hide-substance, and at the same time appears to assist the chemical combinations there occurring; hence a great reduction in the time required for the completion of the process. Many patents have been taken out in this direction, one of the best known being that of See also:

Groth, experimented upon by S. Rideal and A. P. Trotter (Journ. Soc. Chem. Indust., 1891, vol. x. p. 425), who employed copper anodes, ¢ sq. ft. in See also:

AREA

area, with current-densities of o•375 to I (ranging in some cases to 7.5) See also:

ampere per sq. ft., the best results being obtained with the smaller current-densities.

Electrochemical processes are often indirectly used, as for example in the See also:

VILLON, FRANCOIS (1431-c. 1463)

Villon process (Elec. Rev., New See also:

York, 1899, vol. See also:

XXXV

xxxv. p. 375) applied in See also:

Russia to the manufacture of alcohol, by a See also:

SERIES (a Latin word from serere, to join)

series of chemical reactions starting from the production of See also:

ACETYLENE

acetylene by the See also:

ACTION

action of water upon calcium carbide. The production of ozone in small quantities during electrolysis, and by the so-called silent See also:

DISCHARGE (adapted from the O. Fr. discharge, modern decharge, from a med. Lat. discargare, to unload, dis- and earn care, to load, cf. " charge ")

discharge, has long been known, and the See also:

Siemens See also:

INDUCTION (from Lat. inducere, to lead into; cf. Gr. ilrayu yli)

induction See also:

TUBE (Lat. tuba)

tube has been See also:

DEVELOPED

developed for use industrially. The Siemens and Halske ozonizer, in form somewhat resembling the old laboratory See also:

INSTRUMENT (Lat. instrumentum, from insincere, to build up, furnish, arrange, prepare)

instrument, is largely used in See also:

Germany; working with an alternating current transformed up to 65oo volts, it has been found to give 28o grains or more of ozone per e. h. p. hour. E. Andreoli (whose first British ozone patent was No. 17,426 of 1891) uses See also:

FLAT (a modification of O. Eng. flet, an obsolete word of Teutonic origin, meaning the ground beneath the feet)

flat aluminium plates and points, and working with an alternating current of 3000 volts is said to have obtained 1440 grains per e.h.p. hour. Yarnold's process, using corrugated glass plates coated on one side with gold or other metal See also:

LEAF (O. Eng. leaf, cf. Dutch loof, Ger. Laub, Swed. lof, &c.; possibly to be referred to the root seen in Gr. Ma-eta, to peel, strip)

leaf, is stated to have yielded as much as 2700 grains per e.h.p. hour. The ozone so prepared has numerous uses, as, for example, in bleaching oils, waxes, fabrics, &c., sterilizing drinking-water, maturing wines, cleansing foul See also:

BEER

beer-casks, oxidizing oil, and in the manufacture of vanillin. For further See also:

INFORMATION (from Lat. informare, to give shape or form to, to represent, describe)

information the following books, among others, may be consulted :—Haber, Grundriss der technischen Elektrochemie (Munchen, 1898) ; Borchers and M'Millan, Electric Smelting and Refining (See also:

LONDON

London, 1904) ; E. D.

Peters, Principles of Copper Smelting (New York, 1907) ; F. Peters, Angewandte Elektrochemie, vols. ii. and iii. (See also:

LEIPZIG

Leipzig, 1900) ; See also:

Gore, The See also:

Art of Electrolytic Separation of Metals (London, 189o) ; See also:

Blount, Practical Elettro-Chemistry (London, 1906) ; G. Langbein, Vollstandiges Handbuch der galvanischen Metall-Niederschlage (Leipzig, 1903), Eng. trans. by W. T. Brannt (1909) ; A. Watt, Electro-Plating and Electro-Refining of Metals (London, 1902) ; W. H. Wahl, Practical See also:

GUIDE (in Mid. Eng. gyde, from the Fr. guide; the earlier French form was guie, English " guy," the d was due to the Italian form guida; the ultimate origin is probably Teutonic, the word being connected with the base seen in O. Eng. witan, to know)

Guide to the Gold and Silver Electroplater, &c. (See also:

PHILADELPHIA

Philadelphia, 1883) ; See also:

Wilson, Stereotyping and See also:

ELECTROTYPING

Electrotyping (London); See also:

LUNGE, GEORG (1839- )

Lunge, Sulphuric Acid and Alkali, vol. iii. (London, 1909). Also papers in various technical See also:

PERIODICALS

periodicals.

The See also:

INDUSTRIAL

industrial aspect is treated in a Gartside See also:

REPORT (O.Fr. report or raport, modern rapport, from O.Fr. reporter, mod. rap porter, Lat. reportare, to bring back, in poetical use only, of bringing back an account, news, &c.)

Report, Some Electro-Chemical Centres (See also:

Manchester, 1908), by J. N. Pring. (W. G.

End of Article: ELECTROCHEMISTRY

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