162 Messrs. C. T. Heycock and F. H. Neville. 



A current of coal gas or of hydrogen was passed through, a pipe-stem 

 into the crucible ; and this gas, burning over the surface of the 

 molten metal, proved a perfect protection against oxidation. The 

 metal was stirred by a plunging stirrer of graphite. The alloys were 

 made by adding weighed quantities of the second metal in succession 

 to what was originally a weighed quantity of the first metal, and 

 taking the freezing point after each addition. 



Section III. 



This section contains tables divided into parts and into series. The 

 tables give the freezing point and the composition of each alloy, ex- 

 pressed in percentage weights of one of the constituent metals, and 

 also in atomic percentages. By atomic percentage we understand 

 the number of atomic weights of one metal contained in every 100 

 atomic weights of the two metals in the alloy. 



Section IV. 



The complete freezing-point curves given in the paper are for the 

 following pairs of metals Ag-Cu, Ag-Pb, Ag-Sn, Pb-Cu, Sn-Cu, 

 Ag-Sb. But incomplete curves are also given, showing the freezing 

 points of dilute solutions of Bi, Au, N"i, Fe, Al, in copper, and of Bi, 

 Pt, Au, Al, and Tl, in silver. 



It has not been our aim to make a special study of very dilute 

 solutions, but the results we have obtained, when utilised in the equa- 

 tions given in the paper give as the latent heat of fusion of a gram of 

 copper the number 50 calories, and as the corresponding latent heat 

 of silver 27 calories. This latter number is considerably greater than 

 the 21 calories given by Person, and both numbers can only be 

 regarded as provisional. 



The silver-copper curve shows no indication of chemical combina- 

 tion, unless it be the unexpected fact that the eutectic alloy occurs 

 exactly at the composition Ag 3 Cu 2 . The comparatively small value 

 of the two atomic falls makes it improbable that the two metals form 

 monatomic molecules in this alloy. 



In the silver-lead and silver- tin curves, which have a good deal of 

 likeness to each other, the eutectic alloy contains so little silver that 

 the curve consists almost wholly of the branch starting from pare 

 silver. For the first 20 atoms of added metal the lead curve agrees 

 very well, and the tin curve fairly, with the ideal curve of equa- 

 tion (2) ; but with more lead or tin the total depression becomes 

 much less than that of the ideal curve at the same concentration. 

 We are disposed to see in this, not an evidence of chemical combina- 

 tion, but rather an aggregation of the lead or tin atoms into larger 



