How to Concentrate a Solution

By Sean Lancaster
Make a solution more concentrated by evaporating some of the solvent.

You can make chemical solutions by dissolving a solid into water or other suitable solvent. If the solution is too weak you can evaporate some of the solvent to make the solution more concentrated. A simple distillation lets you collect and measure the amount of water removed so you can calculate the new concentration.

Assemble the simple distillation apparatus using silicone grease at each joint and clamp the system to ring stands with 3-prong clamps. The apparatus consists of a round-bottom flask resting in a heating mantle. A Y-adapter attaches to the top of the round bottom flask. Plug the top of the Y-adapter with a rubber stopper and insert a thermometer through the stopper with the thermometer bulb positioned at the middle of the side arm. Connect the water condenser to the side arm. Place a vacuum adapter at the end of the condenser directing the drip tube into a graduated cylinder.

Add boiling chips to the empty round-bottom flask. Fill the round bottom flask with the solution to be concentrated, but do not fill it more than two-thirds full.

Turn on cold water to the condenser. Turn on the heating mantle and slowly increase the temperature setting to the boiling temperature of water, 100 degrees Celsius. Approach the temperature slowly and maintain it until you have evaporated the desired amount of water. Turn the heating mantle off.

Allow the drip tube of the vacuum adapter to completely finish dripping and measure the amount of water removed from the solution.

Tip

Use plastic clips to secure connections between glassware.

Warning

Do not allow the distilling flask to boil dry.

About the Author

Sean Lancaster has been a freelance writer since 2007. He has written for Writers Research Group, Alexis Writing and the Lebanon Chamber of Commerce. Lancaster holds a Doctor of Philosophy in chemistry from the University of Washington.