Mixture Separation Guide

 In this blog I will be demonstrating a few techniques on how to separate mixtures of solids, and liquids. First I will demonstrate how to separate a solid from a mixture of two powders. As you can see, there are two types of powder shere. The dark red powder in the back we will call Substance “A”, and the silver powder in the front will be substance “B”. The powder on the left is actually a mixture of substances A and B. If I wanted to separate substance A from the mixture, I would do this by adding both powders to a liquid which only substance A is soluble in. This means that substance A will dissolve in the liquid, while substance B will remain a powder. First I will pour my mixture into my desiredliquid. Remember, for this to work, only one of the substances should be able to dissolve in this liquid. As you can see, once I pour the mixture intothe liquid, substance A dissolves, while substance B remains a solid and falls to the bottom. To further separate these two, you could usevacuum filtration with a Hirsch funnel. Consult the video on how to perform vacuumfiltration for more information. For the next part of the video I will showyou how to separate a mixture of two liquids. First let’s go over some vocabulary. 

A solvent is a liquid that is used to dissolveother substances, and a solute is a substance, that can be dissolved in a solvent. As you can see, the black powder, or “blacksolute” can only be dissolved in solvent A, and the yellow solute can only dissolvein solvent B. When both solvents are put in the same vial they are actually unable tomix together. Solvent A stays on the top layer because itis less dense, and solvent B is in the bottom layer. When we add that same black solute to thismixture, it will dissolve only in the solvent A layer. Likewise, if we add the yellow solute tothis same mixture of solvents, it will only be able to dissolve in the solvent B layer. So now if we have a liquid mixture of theblack and yellow solutes we can actually separate them by adding them to the solvent mixture. After adding the mixed substances we willhave to shake the vial a little bit to get them to separate. Once it settles, you will notice that theyhave separated into their respective layers. The black solute dissolved in the solvent A layer, andthe yellow solute dissolved in the solvent B layer.

 To further separate these layers you will need a centrifuge tube and a transfer pipette Expel the air from the pipette outside ofthe container, lower the tip of the pipette into the tube, and draw the bottom layer intothe pipette. Then dispense this liquid into the other tube. Be careful not to draw both layers into the pipette as you are trying to separate the two substances The key here is determining beforehand whichliquids your substances, or solutes, are soluble in. Things like acidity, and alkalinity can alsoeffect solubility. Using these methods, you should be able toseparate solid, or liquid mixtures by using solvents with different chemical properties. Good luck, and have fun in lab!