A single cargo tank carries 2,500 gallons of a corrosive liquid in one compartment. How is this packaging classified under the federal hazmat definitions?

49 CFR 171.8 (Bulk packaging definition; see also the 'Cargo tank' definition)

Cargo tanks are bulk packaging almost by definition, which triggers full placarding requirements, even for residue, and bulk-specific marking rules such as ID numbers on both ends or sides. Misjudging a cargo tank as non-bulk could mean a driver skips placarding that federal law actually requires.