( 162 



O = 1\ (l-/i'.f^) = 7; (l_^/i'(l_.^.')•0, 

 which yield : 



/?':=: Tl + t/^J; ..'^Tl + K-V', • . . (11) 



i. e. with oiir vahies of q^ and q^, [3' = 3,659 and x' = 0,523. 



The whole curve EDF or T=f {x') of fig. 3 has here contracted 

 to tlie single point D (see fig. 4), and the curve u4'/)j8' or T = ƒ(-*') 

 is degenerated into a strair/ht line, all whose values coexist with 

 that one ^'alue of :v'. 



This line A'DB' and the point D still represent unstable phases. 



If for this case we calculate the maxima for ,v and y of the two 

 principle branches as we have done above, then we find : 

 A-,«=0,2G, T,„=922°, .V,„=: 0,00088. 

 y,„ — 0,24, T,„ = 439° , y\n — 0,000062. 



The maximum value for .v' ai)pears to have increased to about 5 

 times the value it had with |i' z= 5, and liiat for //' to about 3(5 limes 

 its former value. The maximum value for ?/' now bos hcloir the 

 eutectic point. A siuiple calculation may show that in our case this 

 already happens as soon as ii' becomes smaller than 4,55. The 

 maximum on the other side will recpiire a much smaller value of ji' 

 before it descends below the eutectic point. 



As soon as ^' becomes smaller than ( 1 + V-^ ) '»i" ^vith our 



assumptions <^ 3,60, the curve A'DB' begins to luni u|»\\ai-(l.s and 

 we get the course indicated in tig. 5 for e. g. /J' = 2,5. 



The line A'DB' lies now wholly in the .s'to/^/cM-egion for 7'^ ƒ (./•), 



— being henceforth always positive. The line EDF on the other 

 hand lies av holly in the umtahle region for T=:/{.v'), as easily 

 appears from the expression for — . This latter circumstance how- 

 ever is not permanently fulfilled; by continually diminishing /i', a 

 point of EDF may be reached for which —^ is equal to zero and 



this is a condition for a further change of the shape of the melting- 

 point curve. But this will be treated in another chapter. 



The maximum values for x' and ij' are now the following (namely 



for i?' = 2,5): 



.t.„,= 0,375, r,«=816° , .7;',„= 0,0044. 

 2/,„= 0,357, 7;„=410° , y„,=: 0,0016. 



