The Alchemist Discovering Phosphorus

The Alchemist Discovering Phosphorus is a painting by Joseph Wright of Derby which was finished in 1771, then redone 1795. The full title of the painting is "The Alchymist, in Search of the Philosopher’s Stone, Discovers Phosphorus, and prays for the successful Conclusion of his operation, as was the custom of the Ancient Chymical Astrologers". 
The picture shows an alchemist trying to produce the rare Philosopher's Stone, which could turn metal into gold, but instead, to his surprise, he finds phosphorus. The picture has provoked many different understandings. The picture moved with Wright to Italy in 1773-1775, came back to England, was redone in 1795, but was only sold four years after his death. It is on show at the Derby Museum and Art Gallery. A story was often printed in popular chemical books in Wright’s lifetime, and was widely known.