What process describes where liquid is continuously fed into a still for distillation?

The process that describes where liquid is continuously fed into a still for distillation is continuous distillation. This method allows for a more efficient and uninterrupted process of separating components in the liquid mixture based on their boiling points. In continuous distillation, the feedstock is introduced continuously at a steady rate into the still, while the distillate is also collected continuously. This is ideal for large-scale operations, as it maximizes productivity and reduces downtime associated with starting and stopping batches, which is common in batch distillation.

In contrast, batch distillation involves processing a finite amount of liquid in a single run, which can limit the volume produced over time. Fractional distillation refers to a technique that separates mixtures into component parts (fractions) based on differences in boiling points, and while it can be used in both batch and continuous distillation, it does not specifically denote the continuous feeding of a still. Re-distillation typically refers to a subsequent distillation process that further purifies or refines a product that has already been distilled once. Therefore, continuous distillation stands out as the method that specifically allows for ongoing input and output, making it the correct answer.