Oct. 6, 1887] 



NATURE 



547 



water conduct better than the salt. There may be double de- 

 compositions between those impurities and the salt. Further 

 we know that many salts decompose in water, e.g. magnesium 

 salts. Again HCl separates from a solution of ammonium 

 chloride, and here we have acid and base separate in the solution. 

 He did not know how to avoid this difficulty, and must content 

 himself with pointing out the existence of it. Then another 

 question is. What is it that is decomposed in the decomposition 

 of salts ? Is the process a simple molecular decomposition ? 

 We may a^^k further how hydrides are decomposed. But it is 

 generally assumed that in the liquid it is only the salt which is 

 decomposed. His son had sent a paper on solutions of chloride 

 of copper. He observed that there is a change of colour in 

 very dilute solutions ; and we may be sure that in those solu- 

 tions the salt has combined with the water. We cannot say 

 whether a salt in solution is alone electrolyzed, or the salt in 

 combination with the water. A relation between conductivity 

 and chemical constitution had recently been obtained by Mr. 

 Hartwig in his laboratory. He found that with rising concen- 

 tration the conductivity of solutions of acids attains a maximum 

 earlier the more carbon they contain. In regard to the friction 

 of the salt in the liquid there is no doubt that the undecomposed 

 salt in the liquid has a certain influence, and work must be done 

 to produce motion of the salt in the liquid. 



Prof Quincke said that he agreed with the views of Prof. 

 Wiedemann as to the influence of secondary decompositions in 

 the liquid. It was difficult to distinguish between secondary 

 and primary decompositions. 



Prof. Fitzgerald, F.R. S., read a paper by Mr. F. Trouton 

 and himself On the Accuracy of Ohtn^s Laxv in Electrolysis. — 

 To avoid the difficulties due to heating of the liquid by the 

 current the method which Chrystal and Maxwell used for solid 

 conductors was employed, but the alternation had to be more 

 rapid. The amount of accuracy obtained was approximately 

 1/2000 per cent. ; and up to this Ohm's law was verified. 



On the general question of electrolysis Prof. Fitzgerald said 

 that the usual reasoning was that if the atoms are to be dragged 

 asunder this requires finite E. M. F. On the whole, however, 

 no work is done ; and therefore, he contended, whatever theory 

 may be adopted, it cannot require a finite E.M. F. to detach 

 atoms. He believed that by this the whole Williamson-Clausius 

 hypothesis was swept away. There were no separate atoms in 

 the liquid. If in the case of HCl there were separate atoms of 

 hydrogen in the liquid, surely some of them would escape from 

 the surface of the liquid. 



Prof. S. P. Thompson read a communication from Prof, von 

 Helmholtz on Further Researches concerning the Electrolysis of 

 Water. — Prof. Helmholtz has been working at the question, 

 whether, when you electrolyze water at different pressures, it 

 needs different electromotive forces. He found that in water 

 which was originally free from gases the smallest E.M.F. will 

 send a current through. He likens the difficulty which there is 

 in getting gas to develop in an electrolytic cell originally quite 

 free from gas to the difficulty which is experienced in getting a 

 perfectly clean liquid to boil. 



His apparatus consists of a U-tube, bent over at one end, and 

 there blown into two bulbs, which contain the electrolyte. The 

 electrodes are fused into the glass. One limb of the IJ-tube is 

 open. From the other, which is in connexion with the bulbs 

 containing the electrolyte, there comes off a side tube through 

 which mercury poured into the open limb can escape, and so 

 exhaust the space over the electrolyte to any required extent. 

 An air-bubble is left in the large bulb above the electrolyte. 



In another apparatus there was no air, and the mixed gases 

 collected. With 179 volts at atmospheric pressure a balance 

 was obtained, and the mixed gases did not increase. He finally 

 fixes upon the superior limit of the E.M.F. with atmospheric 

 pressure at 1 775 volt. 



Experiments on the possible Electrolytic Decomposition of 

 Alloys, by Prof. Roberts-Austen, F. R.S. — Experiments were 

 made on gold-lead and silver-lead alloys. The results are abso- 

 lutely negative. No electrolytic action whatever could be found, 

 although cupellation would certainly have detected a variation of 

 l/loo per cent, in the composition. 



Dr. Gladstone and Prof Wiedemann were able to confirm the 

 result from experiments performed by other methods in their 

 own laboratories. 



Sir W. Thomson said it was a most important discovery. 



Experiments on the Speeds of Ions, by Prof. Lodge, F.R.S. 

 — These experiments are still going on. The object is to deter- 

 mine directly the speeds of the ions in a liquid. The current 

 is sent through a tube of liquid which contains some detecting 

 sul)stance. 



At first something to give a precipitate was used, the advance 

 of which could be timed. But this has the disadvantage of re- 

 moving the substance from the tube, because the current does 

 not affect it when it becomes solid. Now he uses fluid detectors 

 —such as some of the aniline bodies — to detect the advance of 

 acidity or alkalinity. Thus, for example, he may have the tube 

 filled with solution of sodium chloride, with a trace of caustic 

 soda, and a body which is coloured in alkaline solution, but 

 which loses its colour when the alkalinity disappears. If now, 

 in the course of the electrolysis, ions from the substance being 

 electrolyzed which will unite with the Na of the caustic soda 

 travel along the tube, they will cause the alkalinity to disappear, 

 and the rate at which this change travels can be measured. 



The composition of the liquid, however, does not remain 

 constant, and therefore we get a broken slope of potential in 

 the tube, because the bad-conducting alkali is turned into the 

 good-conducting acid. This difficulty is got over by making 

 the principal ingredient in the measuring tube the same as the 

 product of the action for any given case. A small addition to 

 its amount is therefore of no consequence. 



The theory of Kohlrausch with regard to the speed of ions 

 was shown to be in accordance with the results. 



On Chemical Action in a Magnetic Field, by Prof. H. A. 

 Rowland. — It had been observed by his colleague. Prof. Remsen, 

 that if a thin plate of iron be placed between the poles of an 

 electro-magnet and then acted on by CUSO4, the copper was 

 deposited inlines very similar to the equipotential lines. Around 

 each pole was a clear space where the iron was not acted on at 

 all. This part of the field is of course the part where the rate 

 of variation of the square of the magnetic field is greatest ; and 

 it occurred to Prof. Rowland that the want of action of the 

 sulphate of copper in this position was due to the attraction of 

 the magnet on the iron. With the help of Mr. L. Bell he had 

 carried out experiments on the point. 



Between the poles of a powerful electro-magnet was placed a 

 glass beaker containing the liquid whose action upon iron it was 

 desired to test. Nitric acid generally acted very well ; so did 

 sulphate of copper, and almost any salt which would deposit 

 metal on iron. In the liquid were immersed two pieces of 

 iron, one of which was pointed. The greater part of each piece 

 was covered with wax, and what was exposed to the liquid was 

 a point in the one case and a plane surface in the other. They 

 were connected through a galvanometer, and a current was 

 obtained which was not reversed on reversing the direction of 

 the current of the electro-magnet. This indicated that the 

 point was protected from the action of the liauid. 



On the Electro-deposition of Alloys, by Prof. S. P. Thompson. 

 — In a mixture of metals which is electrolyzed, the most negative 

 metal comes down first. Prof. Thompson made a series of 

 experiments on solutions of zinc and copper in cyanide of potash 

 solution of different strengths. The electromotive force was 

 measured for each strength of the cyanide of potash solution. 

 The curves representing the E.M.F. for copper and zinc were 

 found to cut at a certain strength of the KCN solution. 

 Beyond this strength copper became positive to zinc. In the 

 ordinary brassing solution he found that it depended on the 

 temperature whether zinc was positive to copper or copper to 

 zinc. 



On the Action of the Solvent in Electrolytic Conduction, by 

 T. C. Filzpatrick. This paper was communicated by Mr. 

 W. N. Shaw. — Mr. Fitzpatrick found that although methyl 

 alcohol has greater conductivity than water, yet a solution of 

 calcium chloride in the former liquid is a worse conductor than 

 an aqueous solution. He found similar results for calcium 

 nitrate, lithium chloride, and lithium nitrate solutions. Solu- 

 tions in elhylic alcohol were also used. He was much impressed 

 with the idea that electrolysis is the electrolysis of molecular 

 aggregates. 



The next paper was by Prof. S. P. Thompson, on the 

 Industrial Electro-deposition of Platinum. He exhibited speci- 

 mens illustrating a new process. 



The Princeton Eclipse Expedition, by Prof. C. A. Young. — 

 The expedition had its origin in his desire to repeat observations 



