2922.21.10.00 - 1-Amino-8-hydroxy-3,6-naphthalenedisulfonic acid; 4-Amino-5-hydroxy-1,3-naphthalenedisulfonic acid (Chicago acid); 4-Amino-5-hydroxy-1,3-naphthalenedisulfonic acid, potassium salt; 4-Amino-5-hydroxy-1,3-naphthalenedisulfonic acid, sodium salt; 4-Amino-5-hydroxy-2,7-naphthalenedisulfonic acid, monosodium salt (H acid, monosodium salt); 4-Amino-5-hydroxy-2,7-naphthalenedisulfonic acid, potassium salt (H acid, monopotassium salt); 4-Amino-3-hydroxy-1-naphthalenesulfonic acid; 6-Amino-1-naphthol-3-sulfonic acid and its salts; and 8-Amino-1-naphthol-5-sulfonic acid and its salts

This HTS category encompasses a specific group of amino-naphthol sulfonic acid compounds and their salts, primarily used as intermediates in the synthesis of dyes and pigments. The listed substances, including Chicago acid, H acid (and its salts), and various other amino-naphthol sulfonic acids and their salts, are characterized by the presence of amino (-NH2), hydroxyl (-OH), and sulfonic acid (-SO3H) functional groups attached to naphthalene rings. Their utility lies in their ability to form vibrant colors when reacted with other chemical components.

Distinguishing this category from its sibling, 2922.21.25.00, is crucial. While both deal with amino-hydroxynaphthalenesulfonic acids, 2922.21.25.00 specifically covers "1-Amino-8-hydroxy-4,6-naphthalenedisulfonic acid, monosodium salt." This current category, in contrast, includes a broader range of these complex naphthalene derivatives, as detailed by the specific chemical names provided in its description, which may vary in the number and position of sulfonic acid groups or the form of salt (e.g., potassium or sodium).

As this is a leaf node within the HTS structure, there are no further subdivisions. Classification at this level relies on precise identification of the chemical compound and its salt form against the detailed descriptions provided. Trade professionals must carefully verify the specific chemical identity of the imported or exported product to ensure accurate classification within this precise sub-heading.