1. The problem statement, all variables and given/known data An unknown compound gave a melting point of 230C. When the molten liquid solidified the melting point was determined to be 131C. Give a possible explanation for this discrepancy. 2. Relevant equations 3. The attempt at a solution I understand that melting point depression arises from impurities within the lattice of the crystallized sample. But, I cannot seem to find why re-melting a "used" MP sample would lead to a MP depression. Most likely the sample was not cooled quickly, but slowly sitting at room temperature, which should allow the crystal lattice to recombine without any impurities within the capillary tube. Any ideas?