Whiz Comics #82 (1947)

Reluctantly walking to the dentist's office one day, Sterling Morris passes a new store, "The Atomic Shop," displaying "Atomic Pills," "Atomic Insect Spray," "Atomic Soap," "Atomic Acid," etc. The shopkeeper, Professor Adam Atomme, claims to have atomic toothache drops that will cure Morris's toothache in a second. He tries it; it works; soon Morris is directing Billy Batson to give the store a plug on the air. Suddenly smoke pours out of Mr. Morris's mouth; his entire tooth has dissolved! Billy SHAZAMs up and Captain Marvel flies out to visit the Atomic Shop. Meanwhile Mr. Atomme has sold a box of atomic breakfast cereal to a scrawny man, building him instantly into a physical powerhouse; this guy goes out to settle a score with a local bully, but his mojo wears off halfway into the beating, and the bully quickly turns the tables. Captain Marvel kiboshes that. Meanwhile at the store, the janitor, Mr. Atomme's ne'er-do-well nephew Archy Atomme, decides to likewise eat a bunch of atomic breakfast food, then go do some crimes, but bumps into Captain Marvel right at the shop's door, and gets punched, but stays on his feet and returns an atomic punch that knocks Cap out the window, then steals a bottle of Atomic Acid, and leaves. Marvel goes after him, after wasting a few moments trying to persuade Atomme to stop selling his dangerous products. At a nearby bank, closed for the night, Archy uses the atomic acid to get inside the vault and steal some big bags of money, but Captain Marvel catches up to him in the lobby and punches him, much harder this time. But Archy fakes unconsciousness, and Marvel picks just the wrong moment to change back to Billy, and he's quickly gagged and tied up. Archy decides to test this acid, which he's just seen dissolve a bank wall and a vault door, to see whether it will dissolve Billy, but very luckily the first drop lands on Billy's gag, SHAZAM, Captain Marvel drinks the rest of the atomic acid with no ill effects. Meanwhile back at the Atomic Shop, there is an accident involving more of the atomic acid, which wrecks the entire shop, putting Prof. Atomme out of business just as he was starting to see things Captain Marvel's way anyway.