42 Mr. J. B. Tayler on the 



was a true eutectic. Of the alloys of lead and tin, those con- 

 taining 2'0 and 5*1 per cent, of the latter were made by 

 adding lead to the 21 per cent, alloy ; as it was thought that 

 the more nearly equal the two portions melted together, the 

 smaller would the percentage error be. In no case was an 

 analysis made. In order, as far as possible, to ensure homo- 

 geneity in the alloys, they were kept stirred until they had 

 nearly cooled down to the solidifying point, and were then 

 poured out into shallow carbon moulds. Both from their 

 behaviour under the file and from their heat of solution, the 

 alloys seem to have been homogeneous, with the exception of 

 the amalgam of zinc containing 25 v 9 per cent, of that metal. 

 This separated into two portions, one of which was lighter 

 and softer than the other. . The former is distinguished as a, 

 and the latter as /3, in the table of results. 



The alloys first experimented upon contained their con- 

 stituents in equivalent proportions, and the heats of formation 

 were found to be small in comparison with those found for 

 brass by Dr. Gait and Mr. Baker. Since the alloys concerned 

 belonged to the class which Matthiessen regarded as solutions, 

 and since they were made at comparatively low temperatures, 

 it was thought that definite chemical combination had only 

 taken place between a small percenlage of the atoms present, 

 and that more reliable results would be obtained by dissolving 

 small quantities of one metal in a large excess of others. The 

 heat of formation per gramme of alloy was found to be higher 

 in the cases tried ; and the heat of formation of the gramme- 

 molecular weight of compound, supposing that the whole of 

 the metal present in small quantity had entered into chemical 

 combination by the exercise of its normal valency, was, of 

 course, immensely greater. The latter is the quantity it was 

 desired to be sure about, the object of the work being to 

 determine the order of magnitude of the chemical forces 

 which effect the combination of metals. The second column 

 of Table II. contains the figures calculated from those in the 

 first column on the above supposition. 



Incidentally it appears that the so-called " mechanical 

 mixtures " (so Matthiessen regarded alloys of lead and zinc) 

 and " solutions " (lead and tin, zinc and tin) contain a small 

 percentage of true compounds, and that eutectic alloys do 

 not necessarily correspond to the greatest evolution of heat. 



Throughout the work I have had the privilege of Prof. 

 Lodge's advice and supervision, and my best thanks are also 

 due to Drs. C. A. Kohn and T. L. Bailey for their kind advice 

 upon several matters of detail. 



