If Y which is ratio of mass of solvent to mass of solvent in liquid free phase: For extract is 0.2 (YD) For extract leaving stage N is 0.4 (YVN) Amount of extract is 100kg (D) Amount of solvent in cascade is 50 (SD) What is the extract reflux?

Correct Answer: 150
Since LR/D = (YD)+SD/D)-( YVN)/YVN-YD, LR 100*(0.2+0.5)-0.4/0.4-0.2=150.