Urine luck.
Today's artwork is The Alchemist Discovering Phosphorus, also known as 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. It is by English painter Joseph Wright, also known as Wright of Derby. The painting may or may not be about the historical discovery of phosphorus, a process which involved the reduction of urine, a fluid rich in phosphates.