2919.90.50 - Other

This HTS category, 2919.90.50, encompasses phosphoric esters and their salts, along with their halogenated, sulfonated, nitrated, or nitrosated derivatives, that do not fall under more specific classifications within the "Phosphoric esters and their salts" heading. Essentially, it acts as a residual category for these complex organic phosphorus compounds when they aren't otherwise defined.

The distinction from sibling categories, such as "Aromatic" phosphoric esters, lies in the structural origin of the ester. While "Aromatic" specifically denotes esters derived from aromatic alcohols, this category is for compounds where the ester linkage is not derived from an aromatic structure, or where other chemical modifications dictate a classification outside of the "Aromatic" sub-grouping.

Within this "Other" category, further subdivisions exist to refine classification. The subcategory 2919.90.50.10 specifically covers "Plasticizers," which are additives used to increase the plasticity or fluidity of a material. The remaining items are captured under 2919.90.50.50, "Other," for phosphoric esters and their derivatives that do not fit the "Plasticizers" definition or any other more precisely defined subcategories.