Aspro Clear tablets contain aspirin and caffeine. Both aspirin and caffeine are soluble in water. When Aspro Clear tablets are placed in water, the aspirin and caffeine dissolve, forming a solution. The solubility of aspirin and caffeine is due to their molecular structure. Aspirin is a weak acid that can dissociate into hydrogen and acetylsalicylic ions. Caffeine is a weak base that can dissociate into hydrogen and caffeine ions. When Aspro Clear tablets are dissolved in water, the hydrogen ions from aspirin and the hydroxide ions from water react to form water molecules. The acetylsalicylic ions and caffeine ions remain in solution.