Why is reflux done in Distillation column ?  & define reflux ratio ?

Why is reflux done in Distillation column ? & define reflux ratio ?

‪@dice-2114‬ What is reflux? What is reflux ratio? What is purity? Why we use reflux on Distillation column? Fully explained in simple language 0:00 what we learn in this video 1:18 why we do reflux/ what is reflux 4:33 what is reflux ratio/ formula for reflux ratio 6:00 discuss what we learn