ON ELECTROLYSIS. 341 



identical if only heat of combination could be regarded as independent of 

 temperature. 



If this were a correct mode of regarding the matter, it would be of 

 the highest interest to be able to calculate dissociation temperatures in 

 this way. Unfortunately, several of the best judges in this country have 

 expressed to the Committee their serious doubts as to the validity of thus 

 stepping, unguided, outside the region of safe knowledge, across the 

 great gap separating ordinary from dissociation temperatures. We wish 

 Professor Willard Gibbs were here to support and strengthen his position. 



These are the main problems at present under discussion among the 

 members of the Committee, and with this summary of them and refer- 

 ence to such of to-day's papers as seem likely to contribute towards their 

 solution, the report proper may be understood to close. 



I think, however, I am only expressing the feeling of the Committee 

 if I say that they view this joint sitting of Sections A and B with great 

 interest, and with the anticipation and hope that it may be the precursor 

 of many other such gatherings during the era oE development in the 

 borderland of chemistry and physics which in many directions they feel 

 to be now imminent. 



Experiments on the possible Electrolytic Decomposition of certain Alloys. 

 By Professor W. C. Robekts-Austen, F.B.S. 



The original suggestions framed for the guidance of the Committee provided for 

 an examination of the question whether molten alloys would conduct electroly- 

 tically, and during the year 1886 various experiments were made in the Mint labo- 

 ratory, the results of which were in all cases negative, but were useful as indicating 

 the method of working which appeared to afford the best prospect of success. The 

 selection of a suitable alloy is by no means easy. It seemed well to begin by 

 employing lead-gold and lead-silver alloys for the following reasons : — Mattbiessen * 

 has shown that these alloys, wben considered from the point of view of their elec- 

 trical resistance, belong to a class described by him as ' sohdified solutions of one 

 metal in the allotropic modification of another.' 



Some work has already been done on the alloys considered as solutions of the 

 precious metals in lead. I have already submitted tc the British Association pre- 

 liminary results on the diffusion of silver and of gold in molten lead,'- and some 

 unpublished experiments of my own have shown that certain sil\-er-lead alloys 

 when poured in spherical moulds, capable of holding about 2'6 kilogrammes of 

 lead, set as a whole without exhibiting any tendency to the re-arrangement of the 

 constituent metals known as ' liquation,' that is, the constituent metals do not 

 readily fall out of solution. Such alloys are those which contain less than three 

 per cent, of silver. The alloy containing 51-06 per cent, of sUver, to which the 

 formida Ag.^Pb may be assigned, also sets as a whole without re-arrangement of 

 its constituents. Guthrie, in an admirable research, interrupted by his lamented 

 death, has shown ^ that an ' Eutectic ' alloy of silver and lead probably contains 

 less than 1-5 per cent, of silver, that is, it is the aUoy of the lead-silver series which 

 has ' a minimum temperature of liquefaction, ... a temperature lower than that 

 given by any other proportion,' and he _ points out that such eutectic alloys are 

 ' neither atomic nor molecular ' in constitution. 



The curves representing the electrical resistance of solid lead-silver and lead- 

 gold alloys are continuous, and do not reveal the existence of any special alloy 

 differing widely in resistance and in physical properties from the rest of the series. 

 In the case of the copper-tin series of alloys, investigated by Matthiessen '' in 1860, 

 by myself " in 1879, and by Dr. Lodge * in the same year, the alloys Sn Cug and 



• Phil. Trans. 1860, p. 161. * Phil. Trans. 1860, p. 85. 



■•^ Report for 1884, p. 675. ^ Phil. Mar/. 1879, vol. ii. p. 57. 



' ' On Eutexia,' Phil. Mag. 1884, vol i. p 462. « lUd. 1879, vol ii. p 554. 



