H Acid Free Acid (4-Amino-5-hydroxy-2,7-naphthalenedisulfonic acid) from Mexico
The free acid form of H acid is specifically enumerated in HTS 2922.21.1000 alongside its salts. Less common than salt forms but used where specific pH control needed in dye coupling. Highly water-soluble despite free sulfonic groups.
Duty Rate — Mexico → United States
15.8%
Rate breakdown
9903.05.5510%Except for products described in headings 9903.05.85–9903.05.92 and 9903.05.94, articles the product of Mexico, as provided for in U.S. note 52 to this subchapter
Import Tips
• Neutralization equivalence point titration confirms free acid content
• Stronger corrosivity requires UN 3265 class 8 designation
• Specialized ventilation for dust exposure during unloading