284 



HAROLD L. ALLING 



"T 1 1 1 — I 1 — i 1 1 r — I" " < 1 1 1 1 <— — 1 1 \ 



KAlSisOe 10 20 30 40 50 60 70 so aoNaAlSisOsKAlSiaOe '° ^° 3o 40 so eo to bo soNaAlSiaOa 



A 



KAISi308'° 20 30 40 so 60 70 ao 90 NaAlSisOsKAISiaOs 'O 20 30 "o so 60 70 ao soNgAisijOb 



Fig. I. — Thermal diagrams of the potash-soda feldspars after Vogt,* Warren,t 

 Dittler,J Makinen,§ and Marc.|| These diagrams have been modified by the writer 

 to bring them up to date, otherwise they represent the originals. 

 Legend for the diagram after Vogt and Warren: 



A. "Melting point" of orthoclase (incongruent melting point). 



B. Melting point of albite. 



E. Eutectic point, 42 per cent of Or. 



iN and qM. Boundaries of miscibUites. Solubility lines, Or and Ab. 



* J. H. L. Vogt, Tsch. Min. Pelro. Milt., XXiV (1905); XXV (1906); XXVII (1908). 

 t C. H. Warren, Proc. Am. Acad. Arts and Set., LI (No. 3, 1915)1 148. 



I E. Dittler, Tsch. Min. Petro. Mitt., XXI (1912), 513. 



§ E. Makinen, Sonderadb. aus. Geol. Foren. Foerhandl. XXXIX (No. 2, 1917), 121-84. 



I I Robert Marc, Chemische Gleichgewischtslehre, p. 102. 



