1892.] On certain Ternary Alloys, 387 



stance that in this compound the two metals are to one another nearly 

 in the ratio of that existing at this central point 



Found. 

 Calculated for SnZn 4 . 



Tin 31-2 28 = 3V5 



Zinc 68-8 61 = 68'5 



100-0 89 100-0 



It will be shown in a future paper, that analogous convergent dis- 

 positions of the lines are observed with other ternary metallic 

 mixtures, also leading to the conclusion that definite compounds are 

 formed ; a well marked case in point is noticed with alloys of lead, 

 zinc, and cadmium, where a marked convergence is observable to a 

 point where the cadmium and lead are in the ratio indicated by the 

 formula CdPb 2 . 



Alloys of Bismuth, Tin, and Zinc. 



The experiments described in Part III, when plotted on the tri- 

 angular system, indicate that the limiting point in the critical curve 

 for mixtures of bismuth, tin, and zinc is situated to the right (zinc 

 side) of the central line of the triangle ; so that in order to determine, 

 with the least amount of error through imperfect intermixture, the 

 conjugate points situated near the limiting point, the mixtures used 

 must contain more zinc than bismuth. Accordingly a number of 

 additional experiments were made with mixtures containing bismuth 

 and zinc in the proportion 1 : 2'5 to 1 : 3"5, and from 12 to 21 per cent, 

 of tin. The figures thus obtained showed that some of the compound 

 ingots previously examined (prepared with equal quantities of bis- 

 muth and zinc) were slightly but sensibly affected by the error due 

 to incomplete intermixture, owing to the preponderance of heavier 

 alloy formed over the lighter one. The following table exhibits the 

 average values finally deduced from these further experiments, together 

 with those of the former series not materially affected by this source 

 of error, at temperatures averaging near to 650 C. It is noticeable 

 that these further experiments show that the numerical value of the 

 excess of tin percentage in the lighter alloy over that in the heavier 

 attains a maximum (of negative sign), and then diminishes again ; 

 a point not shown by the less complete series of values described in 

 Part III. 



Fig. 7, curve No. 1, represents these values, No, 2 representing the 

 analogous figures obtained at 700 800 (Series II, Part III). Ob- 

 viously the critical curve for the higher temperature lies inside that 

 for the lower temperature, as in the case of the lead-zinc-tin alloys 

 above described. The point marked A represents a mixture not sepa- 



