( 524 ) 



where T^ and q^ relate to tin as solvent for example, everything on 

 the right hand side will remain nnchanged, although tin should not 

 be monatomie, but say /^-atomic. For x, the concentration of the 

 dissolved mercury, would then become ?i-times greater, but r/„ would 

 also become ?i-times greater, because the heat of fusion relates to 

 1 mol. = yi-atoms. On the other hand, if the mercury were ??i-atomic, 

 the value of x alone would change; x would then become 7?i-times 

 smaller, and we shall, therefore, observe a /«-times smaller lowering 

 of the melting-point than that, calculated on the basis of mono-atomicity. 

 In this way we might attain to the knowledge of the molecular 

 condition at the ends of the curve, ,c being (for mercury), and 1 

 (for tin). But in order to form further conclusions with other \'alues 

 oi X, the whole of the meltingpoint-line would lia\e to be accurately 

 examined, and this may in many cases become an exceedingly com- 

 plicated matter. 



6. There is, liowe\-er, another way to get to know something 

 about the molecular condition of the solid tin, and that is the com- 

 position of the solid phase, which is in equilibrium w^itli the liquid 

 one. If we equate the molecular potentials of }iiei'cury in the two 

 phases, we obtain : 



- ,' T -V- liT log X -}- — = e\ — c\ T 4- RT log x + '^ , / . 



This further gives: 



e. 



X 



{e-e\) - {c-c^ T = RTlog - + 



V,(l-..y a^a-xf- 



X l{l-\-r'x'y {l^rxy 

 or with e^ — e'.^ := q\, and ^vhh introduction of the meltingpoint T\ of 



puie mercury 



therefore 



RTT\ 



q'Al-~]-=^TiTlo.,--^ id., 



'?0=^ 



T—T' 



L_ 



T. 



X 



aji-xy a.a-x'y 



RT (1 + r xy RT{l-\- r' a^y \ _ 



Now in the liquid condition 



«, = «, X^^ = -y„ X^-, so -- = 7,^; Y X ^- =" ^ X Y X ^- 



5U4,8 50 

 This quantity is therefore 0,1144 X 7^7^^^ X 7^ = 0,745. 



