9902.05.39 - Tetrakis(hydroxymethyl)phosphonium chloride (CAS No. 124-64-1) (provided for in subheading 2931.90.90)

This HTS code, 9902.05.39, specifically covers Tetrakis(hydroxymethyl)phosphonium chloride (THPC), identified by its CAS number 124-64-1. This compound is a chemical substance primarily used as a biocide and flame retardant, often employed in industrial applications such as oilfield operations, textile treatment, and wood preservation. It is important to note that while this entry falls under Chapter 99, it is *provided for* in subheading 2931.90.90, indicating its underlying chemical classification.

As a leaf node within Chapter 99, this classification does not have further subcategories. Its purpose is to denote a specific temporary or special provision for THPC, distinct from the general chemical classifications that would apply outside of this special provision. The distinction from its "sibling" categories, which would represent other temporary legislation or trade agreement provisions within Chapter 99, lies in the precise identification and intended treatment of THPC under this particular code.