9902.01.28 - Dioxosilane (Silicon dioxide amorphous) (CAS No. 7631-86-9) presented in the form of entirely spherical micro-spheres, certified by the importer as having a mean particle size of between 0.046 and 0.054 mm, uniform particle size with a uniformity coefficient of 1.65 or less and specific electrical resistance of 50,000 Ohm cm or more (provided for in subheading 2811.22.10)

This HTS classification, 9902.01.28, specifically covers dioxosilane, commonly known as amorphous silicon dioxide, when presented in a highly specialized form. The critical defining characteristics for this classification are its entirely spherical micro-sphere shape, a certified mean particle size ranging from 0.046 to 0.054 mm, a narrow particle size distribution with a uniformity coefficient of 1.65 or less, and a specific electrical resistance of 50,000 Ohm cm or greater. These precise physical and electrical properties are paramount for its intended use and differentiate it from other forms of silicon dioxide.

Unlike sibling categories within Chapter 99, which often address temporary trade measures or specific import restrictions for a broader range of goods, this subheading is narrowly focused on a technical chemical product with highly regulated specifications. The parent context of Section XXII signifies that this classification falls under special provisions, likely related to temporary legislation or modifications proclaimed pursuant to trade agreements or specific agricultural acts. This implies that the goods classified here are subject to particular import treatments beyond standard tariff classifications.

As this is a leaf node in the HTS database, there are no further subcategories. This means that any product meeting the stringent criteria outlined in the description will fall directly under this specific HTS code. The emphasis is on the importer's certification of the physical and electrical properties, as these are the sole determining factors for classification under this provision, redirecting the classification to subheading 2811.22.10 for its primary tariff treatment.