Secondary Electrolysis. E. ANDRÉOLI.

(Ind. Electrochim., vol. ii., 1898, pp. 36-38; also Génie Civil, 29 June, 1895.)

If an electrolytic cell be divided into three compartments by means of porous partition-walls, and be filled with the same electrolyte, a current passed through it by means of electrodes in the two outer compartments does not produce any change in the central compartment of the cell. If, however, one or more insulated metal plates be immersed in the liquid in the latter, electrolytic decomposition occurs, and to this the Author gives the name of "secondary electrolysis," and states that he is the discoverer of this phenomenon.

As examples of secondary electrolysis he gives the following:1. Deposition of gold from a gold-cyanide solution placed in the central compartment, lead plates being used to receive it. In the outer compartments solutions of sodium chloride are used with a gas-carbon anode, and an iron kathode.

2. Deposition of gold from gold-cyanide solution in central compartment. The outer compartments were filled with the same solution of gold-cyanide, but after many days no change could be detected in the gold contents of the liquid in these compartments.

3. Conversion of sodium bisulphite into hydrosulphite.-The side compartments in this case may contain any electrolyte; the central compartment is fed with a solution of the bisulphite, and only two metal plates are immersed in it. Bleaching operations can be effected by means of the liberated hydrosulphite.

The Author considers that these observations and facts are in conflict with the modern theory of ionic transportation, and he closes his article with a request to electro-chemists for criticisms and suggestions upon the subject.

J. B. C. K.

Electrodes for Electrolysis of Alkali Metal Chlorides.

H. BECKER.

(Ind. Electrochim., vol. ii., 1898, pp. 25-26.)

The materials generally used for electrodes to be employed in salt solutions containing chlorine are gas-carbon, or graphite with which ordinary coke is sometimes mixed to form a moulding compound. High density is one of the chief characteristics required of the product. Girard and Street and Castner convert ordinary carbon into graphite by heating it in closed boxes to the te nperature of the electric arc. Other inventors have described electrodes of high resistance towards chlorine, made by moulding mixtures of powdered carbon and tar under pressure, and heating to 1,000° C. The use of rough blocks of gas-carbon, made into one

conducting medium in various ways, has been patented by many inventors. Others have suggested the use of metallic oxides-as, for example, Gerald and Falconer, peroxide of lead, and Blackman, magnetite or ilmenite.

Electrodes formed of an alloy of platinum and iridium are in actual use in several works producing bleach and chlorates. Platinum alone is not found sufficiently resistant to the chlorine; while platinised electrodes are still less satisfactory. The forms of the platinum-iridium electrodes are very diverse. In the chlorate works they are generally made by stretching thin sheets of the alloy over a wire frame of the same. Kellner has patented a form in which short platinum wires are embedded in an ebonite plate. Hoepfner has patented the use of ferro-silicium; but this was previously described by Uelsmann. Parker and Robinson have suggested chromium phosphide. As materials for kathodes, gas-carbon, iron, and nickel are in actual use. Fluid kathodes have been patented by several inventors: Castner and Kellner have used mercury, while Vautin and Hulin have used molten lead. Finally, Richardson and Holland, and Franchot and Gibbs have patented the use of copper oxide. Short descriptions of many of the above patents are given.

J. B. C. K.

Diaphragms for the Electrolysis of the Alkali Metal Chlorides.

H. BECKER.

(Ind. Electrochim., vol. ii., 1898, pp. 33–34.)

Many materials for diaphragms have been proposed, but only few have received experimental trial. Parchment-paper has been suggested by Le Sueur, Kiliani, Rathenau and Sutter; it is in actual use at Rumford Falls, U.S.A., and at Bitterfeld in Germany. At Leopoldschall parchment protected by a coating of calcium or magnesium oxychloride is used in the electrolytic cells.

Rieckmann describes diaphragms of albuminised paper, or of albumen alone; while Hoepfner has suggested the use of paper or cardboard coated with collodion. Diaphragms of unglazed porcelain or baked clay have been patented by many, and are in actual use in three works. Asbestos as a material for diaphragms has been patented by Roberts and McGraw, Hargreaves and Bird, Riquelle, Wiernick, Waite, Hempel, Richardson, and by Lucius and Bruning. Porous partition walls of Portland cement have been patented by Breuer, Hurter, and by Carmichael. Brief descriptions of all the patents named above are given by the Author.

J. B. C. K.

Storage-Batteries in America. J. WETZLER.

(Electrical Engineer, New York, vol. xxv., 1898, pp. 443-460.)

This is an illustrated account of the works of the Electric Storage Battery Company, of Philadelphia, and of the processes involved in the manufacture of their storage cells. Particulars are also given of some large batteries installed in central stations, tramway stations and lighting plants, and of their application in telephone exchanges, and for telegraphic purposes. The positive plates, "Manchester" type, consist of a grid of antimonious lead, with coils of corrugated lead tape forced into the apertures under hydraulic pressure. The tape is corrugated, cut into lengths, and coiled by an automatic machine, which does the same work as forty to fifty boys. The negative plates are constructed of pellets or pastilles of cast lead chloride-hence the name "chloride accumulator "-held together by a frame of antimonious lead cast round them. They are then placed between sheets of zinc in an electrolyte of zinc chloride, and the pastilles reduced to a highly crystalline form of porous lead. Finally, they are subjected to several washings and constituted kathodes in an electrolytic bath for some hours, to ensure the entire elimination of chlorine from the pastilles. Both the positive and negative grids are cast under a pressure of 100 lbs. per square inch.

E. J. W.

Variation of Capacity of Accumulators with Discharge Rate. J. REYVAL.

(L'Éclairage Électrique, vol. xv., 1898, pp. 143–146.)

W. Peukert found that the current I and time of discharge t are related by the formula

I" tk,

in which n and k are constants for any particular type of cells. The Author gives an account of the results obtained by F. Loppé in verifying this law. A set of curves is given, showing the marked variation of capacity.

W. R. C.

Lead-Zinc and Cadmium Accumulators.

(L'Éclairage Électrique, vol. xv., 1898, pp. 242-244.)

The use of zinc instead of lead for the anodes of accumulators (e.g. that of Regnier) offers the advantages of an increased electromotive force, and also, owing to diminished weight, of an increased specific capacity. Unfortunately, the zinc dissolves when the circuit is open, a defect which is very imperfectly remedied by amalgamation, and hence Commelin and Finot use cadmium instead. In the Werner accumulator, the electrolyte is a solution of the mixed sulphates of zinc, cadmium, and magnesium. In charging, a coherent deposit of zinc and cadmium is obtained, which is practically unattacked when the circuit is open, the magnesium playing a little-understood but most important part. It is found that if a concentrated solution of zinc sulphate is used alone a good deposit of zinc is produced, but the peroxidation of the kathode is feeble; whilst if cadmium sulphate be employed a good deposit and satisfactory peroxidation are obtained, but the electromotive force falls off rapidly during the discharge. On the other hand, with dilute solutions of either salt peroxidation is well affected, but a poor deposit is obtained. The addition of magnesium sulphate allows of the production of all the necessary conditions by means of solutions of moderate strength; nevertheless, it is better to use more dilute solutions for rapid than for slow discharges. Some minor improvements are also made in the construction of the positive plates, with the object of bringing the active material into closer contact with the conducting support. The accumulator has a capacity of 82 watt-hours per kilogram of plates, or 36 watt-hours per kilogram of total weight, the current being 12 amperes to 15 amperes. The electromotive force is 2.4 volts at the commencement, and 1.9 volt at the end of the discharge.

J. W.

Electrical Press-Room.

(West. Electn., vol. xxii., 1898, pp. 221, 222.)

This is an account of the motor-driven presses of the Chicago Record and Daily News. Each press is driven by two motors, one for driving purposes, and a smaller slow-speed motor to manipulate the press in "making ready." making ready." An important feature of this installation is Mr. Stone's electro-pneumatic system of motorcontrol. Compressed air is used to operate the contact-arms of the rheostats, and at a number of convenient points on each press air-valves and push-buttons are located. The handle of an aircock controls, through the specially constructed rheostat, the slowspeed motor, which is used in "dressing the press," or in making

ready to run off an edition. This valve is constructed with three inlets and an exhaust, and can be set, first, to run the press slowly; second, to stop the press; or third, to cause the air to go through a by-pass in such a manner that the press cannot be started from any other point.

W. G. R.

Reiter's Speed-Regulator for Turbines.

(L'Eclairage Electrique, vol. xv., 1898, pp. 290-293.)

An illustrated description of H. Reiter's electric brake, for use as a speed-regulator in the case of turbines working under a small or moderate head of water, in which case a difficulty has always been experienced in maintaining a sufficiently constant speed with large variations of load. The device consists of a small centrifugal governor, which, by raising or lowering a mercury vessel, alters the amount of resistance included in the circuit of the brake electro-magnet. The brake itself consists of a fixed central electro-magnet with re-curved pole-pieces, and an outer ring of steel or iron, which is driven by the turbine, and which absorbs more or less power by the eddy-currents induced in it, according to the degree of excitation of the magnet. The regulator is said to be much quicker in action than one in which a hydraulic brake is used.

A. H.

Electric Governor for Marine Engine. E. PUTato.

(L'Éclairage Electrique, vol. xv., 1898, pp. 293, 294.)

Two mercury-vessels, attached to a longitudinal wall of the ship, communicate with each other by means of a connecting pipe. As the ship pitches, causing the propeller to rise either partially or wholly out of the water, mercury flows from one of the vessels into the other, the effect being to gradually short-circuit a set of resistances connected to contact-pins, which pass into the space above the mercury contained in the vessel near the bow of the ship. As these resistances are cut out, the current through one of a pair of electro-magnets controlling the main steam-valve increases, and the valve is gradually closed. When the bow of the ship rises, the resistances are gradually inserted, and before the last pin rises above the mercury, an auxiliary electro-magnet closes the circuit of the second large electro-magnet controlling the valve, which is thereby opened. In the normal position of the vessel, no current passes through either electro-magnet.

A. H.