April 12. 1888] 



NA TURE 



573 



Rivista Scientijico-Industriale, March 31, — Influence of mag- 

 netism on the electric resistance of solid conductors, by Dr. Fae. In 

 this paper the author explains the conclusions already announced 

 for cobalt and antimony, and describes his further researches 

 on other bodies in connection with the influence of magnetism 

 on their electric resistance. He concludes generally that the 

 resistance of the principal solid conductors undergoes modifica- 

 tions in the magnetic field, such modifications being perceptible 

 enough in the highly magnetic or diamagnetic metals, but 

 most conspicuous in bismuth. In all other metals it is 

 very slight, and at times quite inappreciable. Under like 

 conditions the resistance in the direction of the lines of 

 force increases both for the magnetic and diamagnetic metals, 

 while in the direction normal to the lines of force it diminishes 

 in the first and increases in the second, although under special 

 conditions iron and steel behave exceptionally. These variations 

 of resistance make it probable that Hall's phenomenon depends 

 in effect on a transitory change produced by the magnetism in 

 the structure of the metals, and causing a rotatory variation in 

 the electric resistance. — Dr. Luigi Fritsch describes an 

 industrial product of the nitrate of ethyl. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, February 2. — " On the Voltaic Circles pro- 

 ducible by the mutual Neutralization of Acid and Alkaline 

 Fluids, and on various related Forms of Electromotors." By 

 C. R. Alder Wright, D.Sc, F.R.S., Lecturer on Chemistry and 

 Physics, and C. Thompson, F.I.C., F.C.S., Demonstrator of 

 Chemistry in St. Mary's Hospital Medical School. 



About the beginning of the present century it was noticed that 

 when platinum plates are immersed respectively in an acid and 

 an alkaline fluid {e.g. diluted sulphuric acid and caustic potash solu- 

 tion), and connected with a galvanometer, a much stronger current 

 flows at first than after passing'awhile : which circumstance may 

 be explained by supposing that in virtue of the chemical action 

 taking place between the two fluids a current is generated, the 

 flowing of which necessarily causes electrolysis of the liquids, so 

 that the plates become "polarized" by the evolution thereon of 

 hydrogen and oxygen respectively, whereby an inverse E.M.F. is 

 set up, gas battery fashion. It was shown subsequently by 

 Becquerel that when nitric acid is thus used in conjunction with 

 caustic potash a much more powerful continuous current can be 

 generated, the passage of which is accompanied by a con- 

 tinuous evolution of oxygen from the plate immersed in the 

 alkali, whilst the nitric acid is simultaneously reduced, forming 

 lower oxides of nitrogen: whence the term " pile ^ oxygene " 

 applied to the combination. In this arrangement the hydrogen 

 supposed to be formed electrolytically can never actually make 

 its appearance in the free state, being oxidized whilst nascent by 

 the nitric acid ; so that as the gas battery inverse E.M.F. is not de- 

 veloped, the continuous current passing is not so much weakened ; 

 the oxygen set free by electrolysis consequently passes off" 

 continuously at the other plate. 



It occurred to the authors that, if this reasoning be correct, 

 firstly, other oxidizing acid liquids besides nitric acid should be 

 able to act in the same way, causing continuous oxygen evolution 

 at the plate immersed in the alkali. Secondly, by parity of 

 reasoning, if ordinary dilute sulphuric acid be used on the one 

 side opposed to an alkaline fluid also containing some readily oxi- 

 dizable substance dissolved therein, continuous hydrogen evolution 

 should, under favourable circumstances, be produced at the plate 

 in the acid, the oxygen evolved at the other plate being acted 

 upon while nascent by the oxidizable substance present, so as to 

 be suppressed just as the hydrogen is in Becquerel's «'pile k 

 oxygene." Thirdly, whether oxygen or hydrogen be contmuously 

 evolved, the quantity liberated should be proportionate to the 

 current passing ; so that, if a silver voltameter be included in the 

 circuit, for every milligramme-equivalent (108 mgrms.) of silver 

 deposited i mgrm. -equivalent of gas should be liberated ; i.e. 

 8 mgrms. of hydrogen occupying at o" and 760 mm. 5-6 c.c. ; or 

 I mgrm. of hydrogen occupying ii'2 c.c. 



A number of cells were arranged, consisting of two porcelam 

 basins or beakers, one containing the acid and the other the 

 alkaline fluid united by a siphon tube, or by a thick wick, con- 

 taining or wetted with a strong solution of the salt formed by the 

 union of the acid and alkali {e.g. sulphate of soda when sul. 

 phuric acid and caustic soda were used, and so on). A plate Of 



platinum foil was placed in each fluid attached to a platinum 

 wire, and arranged under an inverted graduated tube filled with 

 the liquid pertaining to that side of the cell, so that any evolved 

 gas could be collected and measured, loss of gas from evolution 

 at the surface of the wire outside the tube being avoided by 

 coating the wire with gutta percha or paraffin wax. A small 

 silver voltameter with a gold plate as negative electrode was 

 always included in the circuit, so as to permit of the deposited 

 silver being determined. Numerous experiments thus made are 

 described, the results of which were always in sensible ac- 

 cordance with the above previsions, a considerable variety of 

 acid oxidizing fluids and alkaline oxidizable solutions being 

 employed. 



These results render it probable that, if, instead of a platinum 

 plate and an oxidizable substance in solution, there be used 

 simple caustic soda or ammonia, and an oxidizable metal, the 

 oxide of which is soluble in the alkaline fluid, continuous cur- 

 rents might be set up (in certain cases at least), even though the 

 metal used have of itself no visible action on the alkaline fluid, 

 apart from its absorbing oxygen dissolved therein or in contact 

 therewith ; for instance, metallic tin or lead in contact with 

 caustic soda, or copper immersed in ammonia solution. On try- 

 ing such experiments, continuous evolution of hydrogen from the 

 surface of the platinum plate immersed in the acid was found in 

 many instances to be readily brought about, the amount evolved 

 being (as might a priori be anticipated) proportionate to the cur- 

 rent passing, i.e. to the quantity of silver deposited in a silver 

 voltameter included in the circuit. By employing an alkaline 

 solution of potassium cyanide, it was found easy to produce the 

 same result when certain metals of the non-oxidizable class (gold, 

 silver, palladium, and mercury, but not platinum) were used 

 instead of really oxidizable ones. 



In most cases the quantity of metal taken into solution in the 

 alkaline fluid was practically identical with that equivalent to the 

 current passing, calculated on the assumption that the nascent 

 oxygen due to the electrolysis combined with the metal to form 

 the lowest oxide thereof, in the various cases respectively. In some 

 few instances a slight excess of metal was dissolved, obviously due 

 either to local action or the effect of small quantities of dissolved 

 air. Two well-marked exceptions to thegeneralrule,however, were 

 noticed : one was tin, which when dissolved in caustic soda in- 

 variably went into solution to an appreciably less extent than cor- 

 responded with SnO ; instead of fifty-nine parts of tin being 

 dissolved for every 108 of silver deposited in the volameter, only 

 quantities amounting to 93 to 97 per cent, of that amount were 

 dissolved, indicating that some little quantity of SnOo was formed 

 as well as SnO, although the latter largely predominated. The 

 other exception was mercury, which in contact with potassium 

 cyanide dissolved to only half the extent due to formation of 

 HggO, mercuric potassio-cyanide being produced. Copper, 

 whether in contact with ammonia or with potassium cyanide, 

 on the other hand, always dissolved in proportions corresponding 

 with CugO, a little excess instead of deficiency being usually 

 noticeable through the secondary action of dissolved air. 



In all these experiments, the results obtained are precisely 

 those due to electrolysis of the salt formed by the neutralization 

 of the acid and alkali in accordance with the scheme (for 

 sulphuric acid and soda) — 



/ H2SO4 I Na2S04 I Na,S04 | aNaOH 



i H2 I S04Na2 I S04Na2 | S04Na2 | H.O + O ; 



where either the hydrogen or the oxygen is suppressed, whilst 

 nascent, by combination with the fluid in contact with which 

 it is evolved, or with the metal in the case of oxygen in the cells 

 last described. . „ ■ c .u- 



Accordingly it might be expected that in all actions ot this 

 kind a quantity of acid on the one hand, and of alkali on the 

 other, proportionate to the current passing, will disappear as 

 such on account of the mutual neutralization thus indirectly 

 brought about. The authors have made a number of titration 

 experiments with a view to obtaining numerical evidence on this 

 point, with the general result of finding that such neutralization 

 always takes place. It may be noticed that if cells be con- 

 structed with platinum electrodes immersed respectively in an 

 alkaline fluid containing an oxidizable substance dissolved there- 

 in, and an acid fluid containing an oxidizing agent {e.g. caustic 

 soda solution of pyrogallol, and sulphuric acid solution of chromic 

 anhydride), continuous currents of very considerable power may 

 be obtained when the internal resistance is diminished sufficiently 

 by using cells of considerable magnitude ; e.g. when made of 



