Reflux Ratio

Reflux is the liquid condensed from the rising vapor which returns to the pot flask.

The Reflux ratio is the ratio between the boil up rate and the take-off rate. Or in other words, it is the ratio between the amount of reflux that goes back down the distillation column and the amount of reflux that is collected in the receiver (distillate).

If 5 parts of the reflux go back down the distillation column and 1 part is collected as distillate then the reflux ratio is 5:1. In the case where all the reflux is collected as distillate the reflux ratio would be 0:1. If no distillate is collected then a reflux ratio is not assigned. Instead we call this "total reflux" or equilibration.

The higher the reflux ratio, the more vapor/liquid contact can occur in the distillation column. So higher reflux ratios usually mean higher purity of the distillate. It also means that the collection rate for the distillate will be slower.

The The M690 microprocessor allows a different reflux ratio to be set for each temperature fraction being collected. This allows solvent recycling protocols to be optimized for each waste solvent type.

Equilibration Time Heating Rate
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M690 Parameters