The fragment of the title binary system up to 30 mol % Th(SO4)(2) was studi
ed. A field of Na2SO4-based solid solution extending up to 12 mol % Th(SO4)
(2) was discovered. Eutectic coordinates: 630 degreesC and 26 mol % Th(SO4)
(2), We suggest that the compound 6Na(2)SO(4) . Th(SO4)(2) exists and melts
peritectically at 685 degreesC.