290 



ELECTEICITY. 



This is another faithful representation of what 

 takes place in Nature H. Matteucci having 

 observed that during storms the oscillations of 

 the needle of the galvanometer are sudden and 

 frequent, while on calm and clear days, the 

 deflection of the needle remains almost con- 

 stant. In other respects .the laboratory ex- 

 periments of the one agreed remarkably with 

 the actual observations of the other. 



Polarization of the Electrodes. At the meet- 

 ing of the French Academy, September 9th, 

 M. Gaugain presented a note on this subject. 

 He made the following experiments, to resolve 

 the question as to the part which each of the 

 electrodes takes in the polarization. In a 

 cylindrical vase he placed a porous cylinder of 

 much smaller diameter, and both vases were 

 tilled with the same liquid. The platinum strips 

 which were to serve for the decomposition of 

 the liquid were placed in the exterior vase, 

 and a third plate of metal was introduced into 

 the porous cylinder ; the third plate, which re- 

 mained constantly out of the circuit traversed 

 by the current, did not experience any polari- 

 zation, and can be successively compared with 

 each of the electrodes when those are polar- 

 ized to saturation ; this comparison gives the 

 measure of the two polarizations of the anode 

 and the cathode. The porous diaphragm served 

 to keep the neutral plate out of reach of the in- 

 fluence of the hydrogen disengaged by the 

 electrolysis. 



The following are the results thus obtained 

 by a series of experiments carried on with a 

 mixture of nine parts by volume of distilled 

 water, and one part of sulphuric acid : 



Polarization of the anode 193 



" cathode 157 



Total polarization 352 



It appears to be of little consequence, if more 

 or less sulphuric acid be added to the electro- 

 lyzed water, provided that this proportion does 

 not fall below a certain limit ; but when it be- 

 comes extremely small the polarization of the 

 cathode increases without the polarization of 

 the anode being sensibly modified. The follow- 

 ing are the results obtained by electroly zing pure 

 water : 



Polarization of the anode 193 



" " cathode 243 



Total polarization 434 



M. Matteucci (Comptes Rendus, January 14, 

 1867) called the attention of the Academy 

 to an experiment which he had made, upon 

 which he depended to prove that the polari- 

 zation proceeded from the gase's adherent to 

 the electrodes. In fact, polarized metals should 

 be considered as fugitive combinations formed 

 by the metals and gases, and 'the author is 

 of opinion that in couples of polarization as 

 well as in Grove's gas-pile, the electromotive 

 force is the affinity exerted on one of the ele- 

 ments of the water by a ga* associated in a 

 particular manner to a metal. 



Improvements of Batteries. The Intellectual 

 Observer for August suggests an improvement 



of the Bunsen battery by the substitution for 

 nitric acid of an aqueous solution of picric 

 acid, by which the evolution of disagreeable 

 and unwholesome gases will be prevented, and 

 the efficiency of the battery not injuriously im- 

 paired. The dilute sulphuric acid may be re- 

 placed^by a solution of sea-salt. The addition 

 also of picric acid to a battery containing but 

 one fluid greatly improves its action. The re- 

 sistance to the current caused by the porous 

 vessel of a DanielPs battery, is removed by a 

 slight modification of its details. Within the 

 outer vessel, which may be made of glass or 

 porcelain, is placed a cylinder of copper much 

 smaller than the outer vessel, but having at- 

 tached to its lower end a disk of copper that 

 just fits on the bottom of the outer vessel. Be- 

 tween the latter and the copper cylinder is the 

 diaphragm and a cylinder of glass or ordinary 

 porcelain, having on the outside, at the distance 

 of one-third of its height from its lower ex- 

 tremity, small projections for supporting a 

 cylinder of zinc. This battery is charged by 

 placing silicious sand in the interior of the 

 diaphragm, and on this sand crystals of sul- 

 phate of copper; then pouring a solution con- 

 taining about 5 per cent, of sulphuric acid gradu- 

 ally into the outer vessel, until it reaches the 

 crystals of sulphate. The electricity passes di- 

 rectly from the zinc to the copper disk, with- 

 out being reduced by passing through a porous 

 vessel. The stratum of dissolved sulphate must 

 never be allowed to rise high enough to come 

 in contact with the zinc ; if it is becoming too 

 high, sand is to be added, or some of the liquid 

 within the diaphragm is to be removed with a 

 syphon, which will cause the sulphate to be 

 driven back on account of the greater height 

 of the liquid in the external vessel. 



M. Montress has found a method of obviating 

 one of the practical difficulties heretofore met 

 with in the case of the galvanic battery ; viz., 

 that the metallic solution produced in the bat- 

 tery, when saturated, was no longer capable of 

 use for the purpose. -He effects his object by 

 the use, in succession, of two metals having 

 very different electro-chemical properties. He 

 first places a cylinder of malleable or cast iron 

 in a vessel, and inside of the iron a prism of 

 carbon; then pours in dilute sulphuric acid. 

 The iron and graphite act as electrodes, and the 

 electricity developed by a single couple of this 

 kind is sufficient to keep a bell-ringing appa- 

 ratus in action for a considerable time. He then 

 concentrates the solution of sulphate of pro- 

 toxide of iron, formed by the battery, and im- 

 merses in it electrodes, which, in this case, 

 consist of zinc and carbon. The zinc is dis- 

 solved, hydrogen liberated, and hydrated pro- 

 toxide of iron set free. The energy of this 

 latter battery will keep the bell-ringing appara- 

 tus in action for several months. M. Montress 

 also avails himself of the fact that oxide of zinc 

 acts as a base with acids, but as an acid with 

 ammonia and other strong bases, for the pro- 

 duction of a cheap and effective battery. It is 



