Batteries with two liquids, that is to say, with bichromate and carbon, with acidulated water in the external vessel and zinc in the porous one, have the great advantage of much diminishing local action, and consequently the wear of the zinc. The internal resistance of the pile is increased by reason of the presence of the porous vessel, and so this kind of battery permits of lighting bnt one lamp at once per battery.

One of the best known models is the 8 element battery of Radiguet (Fig. 88). In this battery it is necessary to change the acidulated water of the porous vessel several times before the bichromate solution is exhausted: but if particular precaution be taken in amalgamation of the zinc, it will be possible to leave the latter continually immersed in the acidulated water without any appreciable wear taking place in open circuit. Consequently, the battery is constantly ready to furnish light through the simple closing of a commutator. But, it is necessary to assure as complete amalgamation of the zincs as possible in order to prevent wear in open circuit.

In order to fulfil this condition, Radiguet in the first place devised the arrangement shown in Fig. 88. The lower part of the zinc dips into a cup containing mercury, which gradually rises on the surface of the zinc and prevents local action. Owing to this simple precaution, the zincs are capable of remaining . permanently in the acidulated water, thus permitting practically of having light at any moment whatever. The keeping of this system in order is therefore reduced to the renewal of the acidulated water every week or fortnight, according to the service required of the battery, and to the renewal of the depolariser every 4 or 5 weeks.

In order to render this system still more convenient and practical, Radiguet has devised some new apparatus, which do away with the replacing of the zinc electrodes and the dismounting of the batteries, by adapting a special negative electrode and using a siphon, which is primed and unprimed by blowing, for the changing of the liquids. The ordinary siphons are primed by suction. This method, which is dangerous in the handling of acid liquids, has prevented its application to the manoeuvring of batteries of large discharge. The Radiguet siphon (Figs. 89, 90), .permits of blowing with the mouth (without any fear of the liquids rising to the lips), or of employing blowing apparatus, such as rubber bulbs, etc, which, never being in contact with the corrosive liquids, last indefinitely. Fig. 89 represents a section of this siphon dipping into a vessel from which ft is desired to retnora the liquid. It consists essentially of two concentric tubes. One branch of the siphon is enclosed in a tube B of larger diameter, having at its lower part an orifice, smaller than the section of the tube A. At its upper part, it is provided with an ajutage D, connected with the bulb F, through a flexible tube E. When B is immersed in any liquid, the level in the tubes B and A is the same as in the vessel.

Things being in this state, if the tube B be blown into, the pressure abruptly increases, and the liquid tends to escape through two apertures - the lower orifice of B and the branch A of the siphon, into which it is forced until the flow through A (that is, the priming) takes place.

Radiguet's 2 liquid battery.

Radiguet's 2-liquid battery.

It is easy to see that the apparatus may serve for the complete or partial emptying of a vessel of any depth by causing the length of the tube and branch A to vary. If, when the siphon is in operation, it is desired to stop it, it suffices to blow inavolume of air greater than the capacity of the large tube B. This air, forced through the tube A, drives out the liquid and nnprimes the siphon. It will be seen, then, that through the same manoeuvre it is possible at any moment to effect a Sow or stoppage of a liquid, as conveniently as by the use of acock, without having to touch the liquid, and whatever be the form and location of the vessel containing it. By means of this apparatus,

Badiguet s 50076Badiguet s 50077Radignet's siphon.

Radignet's siphon.

It is possible, without disturbing a battery of piles or accumulators, to empty any element and wash it as carefully as may be desired.

Bat the most original part of this new style of bichromate battery is undoubtedly the amalgamating support, for, as its name indicates, it permits not only of keeping up the amalgamation of the zincs, bat also of using (instead of pistes and cylinders of zinc of determinate size) shavings, scrap of all shapes, or spheres prepared especially for this purpose.

This eloctrode is formed as follows (Fig. 81). Into a cup of porcelain, or of any other substance not attacked by acid, there is put some mercury containing traces of zino Above this cup is placed a copper receptacle tiled to a hollow rod of the same metal. This is designed to receive fragments of zinc of variable form and size. The central rod constitutes the negative electrode, and contains apertures that permit of the free circulation of the liquid. Its diameter is greater than that of the cup, so that the sulphate of zinc may not fall upon the surface of the mercury and finall y put an end to the amalgama-

In Fig. 92 the mercury cap is connected with the central rod through two strips of copper containing apertures into which passes a pin that likewise traverses the porcelain cup. In this way, all the parts of the electrodes are mechanically connected with each Other and electrically with the mer-

If acidulated water be Introduced into a porous vessel containing an electrode of this kind, the following phenomenon will occur: The mercury will rise upon the copper and zinc, and rapidly cover them with a layer of mercury, which will soon protect them from the action of the acidulated water. If the circuit of the battery be closed, and it be made to discharge a current of normal intensity, the amalgamation will proceed daring the operation. If the battery be made to discharge a very intense current, the mercury will soon disappear from the surface of the zinc; when the battery ceases to discharge, the mercury will ascend the surface of the electrode again and protect it against the action of the acid.

Badiguet s 50079Radiguet's amalgamating supports.

Radiguet's amalgamating supports.

From the following experiment, due to Prof. Daniel, it is possible to give an explanation of these phenomena, which have hitherto been attributed to capillary phenomena not well understood.

If, in a tube containing acidulated water, we place a drop of mercury, and through the tube pass a current of a certain intensity, the mercury will move along the tube in the direction of the current. There is a carriage of the mercury under the mechanical action produced by the current, and the velocity of the mercury's motion is so much the greater in proportion as the current is intenser.

Analogous phenomena must take place in Radiguet's battery. In consequence of the attack on the zinc, and of the currents produced within the battery, a transfer of the mercury takes place. But, as the pellicle of mercury that has formed protects from chemical action the metal upon which it has deposited, the reactions can continue to occur only in the parts not yet amalgamated; consequently, the mechanical effects of the internal currents of the battery cause the mercury to rise progressively to the surface of the liquid, that is to say, until the negative electrode is completely protected by the mercury from the attack of the acidulated water.

Upon the whole, in this element, the internal currents, when any are produced, are utilised in the amalgamation of the zincs attacked, and that, too, the more quickly in proportion as the reaction is more energetic. Despite those important improvements, direct lighting by batteries with two liquids is not yet perfect. As it is possible to supply but one incandescent lamp per battery, the applications are necessarily limited to small spaces. Nevertheless, the improvements pointed out are interesting, for it is not very probable that, in the future, mechanical energy will be capable of being utilised for the lighting of a single lamp, and this application, modest as it is, justifies the use of direct lighting by batteries. Moreover, the combined use of the amalgamating support and of the siphon primer by blowing allows of the batteries being left mounted for a relatively long time, without appreciable wear in open circuit. The maintenance is very easy, since it suffices to throw zinc scrap into the vessel from time to time, in measure as it is consumed, just as we throw coal into a stove, care only being taken to stir the upper fragments and to brush them, now and then, with a hair pencil (like the pencils used by artists) in order to clean the surfaces of contact, (Sci. Am. Sup.)