Possible Clues:

• Pseudo-science that sought to turn base metals into gold
• Search for gold and philosopher's stone
• Legendary gold-making practice
• Chemistry's forerunner
• Medieval chemistry trying to change base metal to gold
• That's the way to make one as good as gold
• Philosopher's Stone its object
• Activity associated with the word ladder formed by 1-, 10-, 70- and 72-Across
• Subject for Dumbledore
• 13-, 20-, 49- and 57-Across, commonly?