In 1731, book lover Franklin created the Library Company of Philadelphia, where this week visitors can see a collection of his papers worth an estimated $3 million to $4.5 million The collection includes writings on Franklin’s experiments with electricity. Sotheby’s A receipt from a book sale, discussions of tax negotiations and a mortgage register may not seem worthy of display in their own right. But throw in records of the early electricity experiments that inspired the lightning rod—and did we mention everything was written or owned by Benjamin Franklin ? Dozens of Franklin’s papers are on display at the Library Company of Philadelphia this week, highlights from a collection of more than 150 items that will go up for auction at Sotheby’s in June. Franklin founded the library in 1731, and it was the first successful lending library in the United States.…