![]() The two solvents must be miscible, i.e., soluble in one another, forming a single layer solution. The second solvent will not dissolve the compound at any temperature. The first recrystallization solvent will dissolve the compound at all temperatures. The chosen recrystallization solvent will dissolve the compound when hot, but not at room temperature. After cooling, crystals are collected by vacuum filtration and washed by rinsing with ice-cold solvent.Įither the one-solvent or the two-solvent method for recrystallization can be used: While cooling, molecules of the same type align in a crystal lattice, forming crystals. ![]() In practice you purify by slowly cooling a hot, saturated solution of your compound. Impurities remain in solution or stick on the outside of the crystal lattice. It works because: 1) different substances have different solubilities in the same solvent, and 2) only molecules of the same compound will fit easily into the crystal lattice of that compound. Recrystallization is a purification technique. What can I do?įAQ: What should I put on the label when handing in my sample?įAQ: When using the two-solvent recrystallization method, why is it necessary to keep both solvents hot when adding?įAQ: Can we add the second solvent first? In the end, all are together anyway.įAQ: If I can choose between the 1-solvent or 2-solvent method, which one should I choose? Do I have to wait until it boils?įAQ: After the solution has cooled down to room temperature, how long should I let it cool in the ice bath?įAQ: Can I put my hot solution directly into the ice bath?įAQ: When we are collecting our crystals using vacuum filtration, what solvent do we use to wash our crystals?įAQ: I have a really lousy suction from that water aspirator. FAQ: The solvent that we use to dissolve the sample for TLC, is that the solvent we will use for recrystallization?įAQ: How many boiling stones should I use?įAQ: When I tested the recrystallization solvent in a test tube it worked, but now my sample won't dissolve!įAQ: How long does it take for the crystals to grow?įAQ: So - once the solvent has reached its boiling point and my crude solid is NOT dissolved, do I add more solvent or do I let it boil longer?įAQ: If we add too much solvent do we just boil it off?įAQ: My sample has dissolved, but my solvent is just hot.
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