Tariff line 2835391000 is specifically reserved for potassium polyphosphates — condensed phosphate salts where potassium is the primary cation. Other polyphosphate salts not described by that specific provision, such as ammonium polyphosphates or mixed-cation condensed phosphates, fall to the residual NESOI lines (2835390000 or 2835395000). Importers should provide the chemical name, cation identity, and chain-length information on entry documentation to support correct classification.

Water treatment is a primary driver, where polyphosphates function as corrosion inhibitors and scale-control agents in municipal and industrial systems. Food and beverage processing uses polyphosphates as sequestrants and emulsifying salts. Specialty ceramics and flame-retardant formulations also consume polyphosphate inputs. The specific end-use sector influences both the grade specification required and the regulatory review that may apply at entry.