2920 - Esters of other inorganic acids of nonmetals (excluding esters of hydrogen halides) and their salts; their halogenated, sulfonated, nitrated or nitrosated derivatives:

HTS code 2920 encompasses a broad range of esters derived from inorganic acids of nonmetals, with the exclusion of esters of hydrogen halides. This category also includes the salts of these esters and any derivatives thereof that have undergone halogenation, sulfonation, nitration, or nitrosation. These compounds are distinct from other substances within Section VI, Chapter 29, by their specific chemical structure involving inorganic acid esters and their subsequent modifications.

Unlike the live animals and animal products found in Chapter 1 through 5, or other organic chemical classifications that focus on carbon-based structures like alcohols, ethers, or amines, HTS 2920 specifically targets inorganic acid esters. For instance, while organic acids and their derivatives are classified elsewhere, the defining characteristic here is the inorganic acid component of the ester linkage. This category is crucial for distinguishing between organic and inorganic chemical classifications based on the nature of the acid from which the ester is formed.

The subcategories within 2920 provide further specificity. For example, specific entries for thiophosphoric esters (phosphorodithioates) and phosphite esters highlight key types of inorganic acid esters that have significant industrial applications, often as pesticides or flame retardants. The explicit listing of Endosulfan, a specific organochlorine pesticide, under 2920.30.00.00 illustrates the granular detail provided within this HTS code to ensure accurate tariff application for widely used, yet potentially regulated, chemical compounds. The "Other" category serves as a residual classification for inorganic acid esters not otherwise specified.