1892.] On certain Ternary Alloys. . 373 



confirm these conclusions ; when the proportions of the constituents 

 are such that approximately equal quantities of the two different 

 ternary alloys are formed, the error due to incomplete intermixture 

 is generally a minimum; this obviously happens when the con- 

 stituents are used in such proportions as to represent an "ideal " 

 alloy corresponding approximately with the central point of the tie- 

 line uniting the two conjugate points. When, however, the propor- 

 tions of the constituents differ materially from these, representing an 

 " ideal " alloy considerably nearer to one conjugate point than to the 

 other, so that one of the two ternary alloys is formed in much larger 

 quantity than the other, the effect of incomplete intermixture becomes 

 more marked, more especially when the heavier of the two alloys 

 largely preponderates. 



In cases where the critical curve is approximately symmetrical 

 with respect to the central line of the triangle drawn from its apex 

 perpendicular to the base, so that the " limiting point " lies near to 

 the apex, the minimum error due to incomplete intermixture is 

 accordingly observed when the two immiscible metals, A, B, are used 

 in approximately equal quantities throughout. If, on the other hand, 

 the critical curve is unsyminetrical, in order to minimise the error 

 due to imperfect intermixture (more especially as regards those parts 

 of the curve where the proportion of the " solvent," C, is greatest), 

 the other two metals, A, B must not be used in equal quantity, but 

 the one or the other must be in excess according as the " limiting 

 point" lies on the right or the left-hand side of the central line. 

 Thus, as shown below, in the case of mixtures of chloroform, acetic 

 acid, and water, the limiting point lies considerably to the left 

 (chloroform side) of the central line ; similarly with mixtures of lead, 

 silver, and zinc, the limiting point is also considerably to the left 

 (lead side) of the central line. In such cases the heavier of the two 

 immiscible constituents, A, B (chloroform, lead) must be made to pre- 

 dominate considerably over the lighter one (water, zinc), in order that 

 approximately equal quantities of the two ternary mixtures may be 

 formed. On the other hand, with mixtures of lead (or bismuth), tin, 

 and zinc, the limiting point lies sensibly to the right of the central line 

 (zinc side) ; so that to determine as accurately as possible the positions 

 of the conjugate points situated towards the limiting point, zinc must 

 be made to predominate over lead (or bismuth) in the mixtures 

 employed. 



The effect of this in practice is that in order to trace out the 

 critical curve for a given trio of metals the most expeditious way is to 

 begin by preparing two or three mixtures with small quantities of 

 solvent C and approximately equal quantities of A and B ; from the 

 results obtained with these mixtures, represented graphically on 

 Stokes' triangular system, a fair idea can generally be formed as to 



