Phodolite

Phodolite is a volatile substance that produces acid clouds when jostled.

"Plus One"
Doc Greene had a shipment of Phodolite brought to Griffin Rock over the GroundBridge on a specially-designed trailer. Unfortunately partway through its journey to the laboratory, one of the crates fell from the trailer, and the Rescue Bots had to scramble to get a compound from Doc Greene to neutralize the resulting acid cloud.