( 602 ) 



Tliis difference is further shown bv the different crystallisation })aths 

 wliich on further coolin^ti' are traversed by mixtures of the same 

 gross composition. 



Tliese crystallisation paths start i]i each of the regions mentioned 

 from th(^ point re|)resenlijig tiie meltijig ]u)int of the solid pliiise, 

 tliat is from A, 1) and E respectively, and indicate the series of 

 mother H(|uors which remain, during a continued cooling, at each 

 temperature. The ci'\ s(allisati(»n ])atlis in tlie tii'st region end in HI 

 or IG, tliose for the second in Kl or IG, for the third in HI or KI. 

 The lines 1 and II schenmticaliy indicate two similar paths in the 

 last region, the xcrtical line EE' is a tiiird one which applies to a 

 litpiid of the gi-oss composiiion SCl^. 



As soon as the ci-ystallisation paths ari-ive at HI, Kl or Gl, the 

 subse(|ueiil solidilication takes place along these lines, each time 

 with (lep(»siti()n of two solid phases : CI, -|- '^^^'14 o» HI, S^CL + '^^'^a 

 on Kl and ('1, -|- S.Cl., (»ii Gl. 



Finally the last liipiid solidities in I to a ternary entecticum of 

 the three |)liases. 



This \yould be (he slate of alfairs if — as has beeji said — ^C\^, 

 S.^Cl.^ and ('1., \yere miscible in all proportions without transformation. 



If, however, SGl^ were a dissociable compound whose formation 

 and decomposition led lo com})lete e(piilibria at all solidification 

 temperatures, iheii instead of the soliditicatioji described another 

 would occur along the lines AH', H'E'K', K'D causing the system 

 to ap|)ear as a binary one in which occurs a componnd which 

 enters iido equilibrium with its components in the liquid condition. 

 The position of these lines Ayilhin the tigui-e of the ternary system 

 is determined by the degree of dissociation of the liquid componnd. 

 If this is e.vtreuiely small, these lines a]tproach to AH, HEK and 

 KD, if very large they approximate to AG and (41) and the com- 

 pound does not appear as a solid j)hase. Solid Cl._, is deposited along 

 AH', solid S(1, along H'E'K', solid S.,C1., along K'D; H' and K' 

 are two eutectic points whei-e com|)lete solidification takes place. 

 These three lines are not only the fii'st series of solidifying i)oints of 

 the ditferent mixtures, but at the same time the crystallisation paths 

 of all mixtures. 



Now with mixtures of S./'l._; and (M._j neither the first nor the second 

 case is quite realised. At the low temperatures at which the soli- 

 difications take ]dace, (!1.,. >S./3I.j and SCI^ behave as independent 

 components; foi- instance Gl., and S./'l., may be mixed in the ii(piid 

 condition without entering into combination and in this way the 

 two solidifying lines AG and GD (fig. I and 2) of these mixtnres 



