The unknown solid is removed by rinsing with water while the PDB is removed by rinsing with alcohol.
Solvents are substances which dissolve other substances to form solutions or mixtures.
Water is used as a solvent for inorganic substances while organic solvents such as alcohol or kerosene are used as solvents for organic substances such as PDB.
Alcohol is added to the test tube containing PDB, which then dissolves. The tube is rinsed with more alcohol until all the PDB dissolves.
Therefore, the unknown solid is removed by rinsing with water while the PDB is removed by rinsing with alcohol.
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