290 MOREY ART. G 



tween the metastable prolongation of curve, K2O • Si02 • ^H20 

 + K2O -28102 + L + V (6c), and the stable portion of KsO-SiOs 

 + K20-Si02-|H20 + L + V (10&). The position of the latter 

 curve being fixed, the position of the curves, K2O-Si02 + 

 K2O -28102 + L + V (6c/) and K2O • SiOg • IH2O + K20- 28102 + 

 L + V (6c), must either be as shown at Qi, Fig. 7, or the position 

 of these curves in regard to the curves, K2O • 28102 + K2O • 8102 

 + K20-8102-IH20 + V (10a) and K2O-8IO2 + K2O - 8102 • ^HgO 

 + L + V (106), must be reversed. That the latter arrangement 

 cannot be correct is shown by the fact that If K2O • 8102 - IH2O 

 - L - K2O • 28IO2 all lay upon a straight line, the curve, 

 K20-8i02-|H20 + K.O- 28102 + L + V (6c), would comcide 

 with the curve, K20-8i02 + K2O • 8102 • iH20 + KgO- 28102 + L, 

 the p-t curve of the condensed system. But such a coincidence is 

 possible only with the arrangement shown in Fig. 7 ; the reversed 

 arrangement cannot be the correct one. 



In order to show further the relation between the composition 

 diagram and the p-t diagram, let us consider under what con- 

 ditions the curves, K2O-SIO2 + K2O - 8102 • JH2O + K2O- 28102 

 + L (the p-t curve of the condensed system) and K20-Si02 

 + KsO- 28102 + L + V (6d), will coincide stably. For 

 this coincidence to take place, it is necessary that the 

 phases, L, K20-8i02 and K20- 28102, lie on a straight line in 

 the composition diagram (Fig. 6), which Intersects internally 

 the line, V-K20-8i02-|H20. On reference to Fig. 6 we see 

 that before the phases can take on the position mentioned above, 

 it will be necessary for the phases, K20-8i02, K2O • 8102 • IH2O 

 and K20- 28102, then the phases, V, L, and K20-Si02, to 

 fall on straight lines. But in the y-t diagram, the first of these 

 will result in the curves, KsO-SiOg + K2O • 8102 • IH2O + 

 K2O • 28102 + L and K2O • SiOs + K2O • 8102 • IH2O + K2O • 28102 

 + V (10a), approaching each other, coinciding, then again 

 diverging, having changed places. 8imilarly, as a result of 

 the second triplet of phases getting on a straight line, the 

 curves, K20-8i02 + K20- 28102 + L + V {M) and K20-8i02 + 

 K20-8102-IH20 + L + V (10a) will change places. The 

 curves, K20-8102 + K20-8102-^H20 + K2O ■ 28102 + Land 

 K20-Si02 + K2O -28102 + L + V {M), now lie next to each 



