What treatment chemical is corrosive, dense, and an oily liquid and is available in strengths of 62%, 78%, and 93%?

• A. sodium hexametaphosphate
• B. zinc orthophosphate
• C. caustic soda
• D. sulfuric acid

Answer: (D)

In water treatment, identify a chemical by its physical properties and common concentrate strengths. The description—corrosive, dense, and an oily liquid available in 62%, 78%, and 93%—fits sulfuric acid. It’s a strong mineral acid that is highly corrosive to metals and skin, and concentrated sulfuric acid is very dense and viscous, often described as oily. The 62%, 78%, and 93% strengths are typical commercial forms for bulk dosing in treatment processes.

Sodium hexametaphosphate and zinc orthophosphate are generally solid or slurry materials used as sequestrants or corrosion inhibitors, not dense oily liquids. Caustic soda is a strong base and while it can be supplied as concentrated solutions, it isn’t described as an oily liquid and its common concentrations differ from the ones listed.