2837.20 - Complex cyanides:

This category, HTS Code 2837.20, encompasses "Complex cyanides." Unlike simple cyanides or cyanide oxides, complex cyanides are inorganic chemical compounds where the cyanide ion (CN-) is bonded to a central metal atom or metalloid, forming a stable complex anion. These compounds are characterized by the presence of coordinated cyanide ligands. Examples include ferrocyanides and ferricyanides of alkali metals or alkaline earth metals.

The distinction between this category and its sibling, "Cyanides and cyanide oxides" (which would typically cover compounds like sodium cyanide, potassium cyanide, or hydrogen cyanide), lies in the structural arrangement. Simple cyanides involve a direct metal-cyanide bond, whereas complex cyanides feature a central metal atom surrounded by multiple cyanide ligands in a coordination complex. This structural difference often imparts distinct chemical properties and applications.

Within HTS 2837.20, we find further subdivisions to ensure precise classification. The subcategory 2837.20.10.00 specifically covers "Potassium ferricyanide," a commonly encountered complex cyanide. All other complex cyanides not otherwise specified fall under the residual category 2837.20.51.00, "Other." This hierarchical structure allows for the granular identification of various complex cyanide compounds based on their specific metallic component and chemical form.