The substance which is dissolved in a solution is called:
solvent
colloids
solute
precipitant

The substance which is dissolved in a solution is called solute.

Explanation:

Solution is made up two parts:

1) Solute : The substance which is dissolves in a solvent to give a solution.

2) Solvent : The liquid substance in which solute is dissolved is known as solvent.

                             Solution = Solute + Solvent

For example : Salt as solute and water as solvent in salt solution.

a saline water is fed to a reverse osmosis unit at flow rate o rotameter connected to reject (retentate) line reads 8 installed in reject and permeate line reads 15.2 milli siemens/cm and 300 micro siemens/com respectively.