Fifteen mol% phenol in water is to be differential-batch-distilled at 260 torr. What fraction of the batch is in the still-pot when the total distillate contains 98 mol% water? What is the residue concentration?

Vapor–liquid data at 260 torr [Ind. Eng. Chem., 17, 199 (1925)]:

x, wt% (H₂O): 1:54 4:95 6:87 7:73 19:63 28:44 39:73 82:9 89:95 93:38 95:74

y, wt% (H₂O): 41:10 79:72 82:79 84:45 89:91 91:05 91:15 91:86 92:77 94:19 95:64