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26 an allowance for public accountants who are not members of any of the institutes and societies mentioned above, it would appear that about 4000 persons were, at the beginning of the year 1900, practising as public accountants in the United Kingdom. (J. G. Gr.)

Accra., See Gold Coast.

Accrington, a municipal borough- (1878), in the Accrington parliamentary division of Lancashire, England, 19 miles K. of Manchester by rail. Modern erections are Established, Free, Congregational, Baptist, and Methodist churches, and a municipal technical school. Dye-works, chemical manufactures, and manufactures of machinery for the cotton-mills have been established. Area, 3425 acres. Population in 1881, 31,435; in 1891, 38,603; in 1901, 43,076.

HE early study of electrolysis made scientific men oxidations, the action penetrates farther into the plate, furnishing time a larger quantity of spongy Pb02 on one plate and acquainted with what were called secondary currents each of spongy lead on the other. It follows that the duration of the and polarization. The former were first used by Grove, successive charging currents also increases. At the beginning, a whose gas battery may be called the first accumulator; but few minutes suffice; at the end, many hours are required. After systematic search for the best effects was not undertaken till the first six or eight cycles, Plante allowed a period of repose 1859, when Plante began a masterly and fruitful investi- before reversing. He claimed that the Pb02 formed by reversal repose was more strongly adherent, and also more crystalline gation. He soon produced his well-known battery, a cell after than if no repose were allowed. The following figures show the with higher electromotive force and greater current-yielding relative amounts of oxygen absorbed by a given plate in sucpower than any other practical combination. He obtained cessive charges (between one charge and the next the plate these results by putting lead plates into dilute sulphuric stood in repose for the time stated, then was reduced, and again acid and sending a current through; after a few reversals charged as anode):—

Separate Periods of he found one plate to be covered by peroxide of lead, the Relative Amount of Charge. Repose. Peroxide formed. other with a porous mass of lead. He set himself to accumulate energy in the cell, by which he meant the First 1-0 18 hours Second formation of a quantity of the active materials. The 1-57 2 days Third' 1names given to Plante’s first cell have been frequently Fourth 24 „ misunderstood. The terms secondary battery, storage 2 Fifth 2-43 battery, and accumulator have been taken to indicate that and so on for many days.—(Gladstone and Tribe, Chemistry of there was an accumulation or storage of electricity or of electric current; but the error is not Plante’s, as is clear Secondary Batteries). Seeing that each plate is in turn oxidized and then reduced, it is evident that the spongy lead will increase from his declaration that his couple is able to give dis- at the same rate on the other plate of the cell. The process of charges of long duration, or to retain its charge for a long “ forming ” thus briefly described was not continued indefinitely, time, “et d’emmagasiner ainsi le travail chimique de la but only till a fair proportion of the thickness of the plates was pile voltaique.” The value of the cell arises from a happy converted into the spongy material, Pb02 and Pb respectively. After this, reversal was not permitted, the cell being put into combination of properties. The three active materials use and always charged in a given direction. If the process of are peroxide of lead, spongy metallic lead, and dilute forming by reversal be continued, the positive plate is ultimately sulphuric acid. Of these, the peroxide is an excellent all converted into Pb02 and falls to pieces. Plante made excellent cells by this method, yet three objecdepolarizer; the lead is a sufficiently good electropositive were urged against them. They required too much time to metal; and the dilute sulphuric acid has a very high con- tions “form”; the spongy masses (Pb0.2 more especially) fell off for ductivity for an electrolyte. Moreover, the two solid want of mechanical support, and the separating strips of caoutsubstances are not only themselves insoluble in the dilute chouc were not likely to have a long life. The first advance acid, but the sulphate of lead formed from them in the was made by Faure (1881), who greatly shortened the time required course of discharge is also insoluble. Consequently, it for “forming” by giving the plates a preliminary coating of red whereby the slow process of biting into the metal was remains fixed in the place where it is formed; and on the lead, avoided. At the first charging, the red lead on the -f electrode is passage of the charging current, the original Pb02 and Pb changed to Pb02, while that on the - electrode is reduced to are reproduced in the places they originally occupied. spongy lead. Thus one continuous operation, lasting perhaps Thus there is no material change in the distribution of sixty hours, takes the place of many reversals, which, with of repose, last as much as three months. Faure used masses of active material. Lastly, the active materials periods felt as a separating membrane, but its use was soon abolished are in a porous, spongy condition, so that the acid is by methods of construction due to Yolckmar, Sellon, Swan, and within reach of all parts of them. The resistance of the others. These inventors put the paste not on to plates of lead, cell is low, while the energy of the chemical action to but into the holes of a grid, which, when carefully designed, affords good mechanical support to the spongy masses and does which it gives rise imparts a high electromotive force. away with the necessity for felt, &c. They are more satisfactory, as supporters of spongy lead than of the peroxide, since Plante carefully studied the changes which occur in the forma- however, at the point of contact in the latter case the acid gives rise to a on Plante’s ^ ’ charge, discharge the cell. acid, In forming, local action, which slowly destroys the grid. Disintegration II he placed two and sheets of lead inof sulphuric separat- follows sooner or later, though the best makers are able to defer ing them by narrow strips of caoutchouc (Fig. 1). the for a fairly long time. Efforts have been made by When a charging current is sent through the cell, the hydrogen Tribe,failure and others to dispense with a supporting grid liberated at plate A for theFitzgerald, plate, but these attempts have not yet been escapes, a small quantity successfulpositive enough to enable them to compete with the other possibly being spent in re- forms. ducing the surface film of oxide generally found on The following description of well-known forms of cells lead. Some of the oxygen will illustrate the methods adopted at the present time. is always fixed on the Plante Type. — “Chloride Accumulator” cells derive positive plate B, forming a surface film of peroxide. their name from the fact that chloride of lead is used After a few minutes the in making the negative plates. There is no chloride Fig-1current is reversed, plate chlorine or chloride in the cell when ready accumuA is peroxidized, while the peroxide previously formed on B is reduced to metallic lead in a for use. For the negative plates, the chloride tators. spongy state. By repeated reversals, the surface of each plate is of lead is melted in large iron pans at a temperature of alternately peroxidized and reduced to metallic lead. In successive about 600° C., and then carried by plumbago crucibles to a