2908.99.03.00 - 2,5-Dihydroxybenzenesulfonic acid, potassium salt; 3,6-Dihydroxy-2,7-naphthalenedisulfonic acid; 3,6-Dihydroxy-2,7-naphthalenedisulfonic acid, sodium salt; 4-Hydroxy-1-naphthalenesulfonic acid, sodium salt; 1-Naphthol-3,6-disulfonic acid; and 2-Naphthol-3,6-disulfonic acid and its salts

This HTS category, 2908.99.03.00, encompasses a specific group of sulfonated derivatives of phenols and phenol-alcohols, focusing on those that contain only sulfo groups. It includes compounds such as 2,5-Dihydroxybenzenesulfonic acid (and its potassium salt), 3,6-Dihydroxy-2,7-naphthalenedisulfonic acid (and its sodium salt), 4-Hydroxy-1-naphthalenesulfonic acid (and its sodium salt), 1-Naphthol-3,6-disulfonic acid, and 2-Naphthol-3,6-disulfonic acid (and its salts). These are primarily organic compounds characterized by the presence of hydroxyl and sulfonic acid functional groups attached to aromatic rings, often utilized as intermediates in dye manufacturing and other chemical processes.

This particular subheading is distinguished from its siblings by the precise chemical structures and specific sulfo-group configurations detailed in its description. For instance, sibling 2908.99.06.00 specifically covers 4-Hydroxy-1-naphthalenesulfonic acid (also known as 1-Naphthol-4-sulfonic acid), a distinct isomer. Similarly, 2908.99.09.00 addresses a different naphthalenedisulfonic acid derivative, 1,8-Dihydroxynaphthalene-3,6-disulfonic acid, and its disodium salt. The current category functions as a residual "Other" for sulfonated derivatives that do not fit into these more specific sibling classifications.

As this subheading is a leaf node, it represents the most granular level of classification within this branch of the HTS for these specific compounds. Therefore, there are no further subcategories to introduce. Classification under 2908.99.03.00 is determined by the exact chemical identity matching one of the listed substances or its salts, ensuring precise tariff application for these specialized organic chemicals.