Which dialysis tube acted as a control?

In a dialysis tube experiment, the dialysis tube that does not contain the semipermeable membrane acts as the control. This tube is typically filled with the same solution as the experimental dialysis tube, but without the presence of the semipermeable membrane. The purpose of the control tube is to provide a reference point against which the experimental dialysis tube can be compared, allowing for the observation and analysis of any changes that occur in the experimental tube due to the presence of the semipermeable membrane.