I’m looking looking for a book about these two kids finding a sulfur smell on their campus, then magically leads to a magician and about elixirs. I read this as a kid in 24 now. I believe there could possibly be another book to it as well.
I’ve been searching very hard and can’t seem to find a lick of anything. The cover was kind of burgundy and had a blue reflective streak on the cover with a magic hat. The cover was also matte.
I think what you're remembering is "The Alchemyst" by Michael Scott, first in his Nicholas Flamel series. The cover, burgundy and blue, sort of matches your memory. In the series Flamel is immortal, having discovered the elixir of life, which also fits what you remember.
What really clinches it (for me) is your description of two kids IDing the magician by the sulfur smell. From this link:
Thursday, May 31st started out like any other day for Josh and Sophie Newman. Staying with an elderly aunt in San Francisco for the summer, the fifteen-year-old twins had been lucky enough to find jobs (Josh at a bookstore and Sophie at a tea and coffee shop) across the street from one another. That's where they were on this previously ordinary Thursday - at work. Josh, in fact, was in the basement of The Small Book Shop (owned by Nick and Perry Fleming) when a horrid smell of sulfur, overlaid with the sharp tang of peppermint, became so overpowering that he had to dash up into the shop for some fresh air. What he saw when he popped his head out of the basement hatch was clearly impossible, but nevertheless happening right before his eyes. Nick Fleming and a small dapper man in a grey suit were hurling balls of energy at one another. In other words, they were battling with magic.
It’s a series of books called The Secret Series by Pseudonymous Bosch aka Raphael Simon.
In The Name of This Book Is Secret, a real estate agent for the deceased named Gloria finds a mysterious box called "The Symphony of Smells" in a dead magician's house, which she drops off at Cass' grandfather's junk store. Cass takes the Symphony of Smells to school with her the next day. That day, while she investigates the reason for a rat dying in her schoolyard, she meets Max-Ernest, who talks too much, loves jokes, and has divorced parents. Max-Ernest tries out one of his jokes on Cass, who tells him that his joke doesn't make sense, thus fostering a conversation between the two.
Cass shows Max-Ernest the Symphony of Smells, and they decode a message for help hidden inside it. Cass and Max-Ernest decide to visit the dead magician's house to find out why he needed help. Now collaborators, Cass and Max-Ernest go to investigate the dead magician's house and find the magician's mysterious journal hidden in his secret study. However, Gloria comes in with a young couple looking for a house - Ms. Mauvais and Dr. L. This couple is looking for the magician's journal and when they see the kids leaving with it, they follow Cass and Max-Ernest and utter threats for hours, however the kids end up escaping.
Quote from the book:
After her experience with Amber and Veronica, Cass had vowed never to discuss her predictions with anyone again. But she made an exception for Max-Ernest because he seemed so knowledgeable about toxic waste. By the time they returned to the soccer field with the laboratory gloves, Cass had told him all about the dead magician, the dead mouse, and the mysterious sulfur smell.
