9902.01.27 - Dioxosilane (Silicon dioxide amorphous) (CAS No. 7631-86-9) entirely spherical micro-spheres of mean particle size of between 0.007 and 0.020 mm, uniform particle size with a uniformity coefficient of 1.65 or less, trace metal impurities less than 70 ppm, specific electrical resistance of 50,000 Ohm cm (provided for in subheading 2811.22.10)

HTS Code 9902.01.27 classifies a highly specialized form of amorphous silicon dioxide, specifically dioxosilane. The key defining characteristics of these micro-spheres are their uniform, spherical morphology, with a mean particle size falling between 0.007 and 0.020 mm. Further stringent technical specifications include a uniformity coefficient of 1.65 or less and exceptionally low trace metal impurities, below 70 ppm. Crucially, the material must possess a specific electrical resistance of 50,000 Ohm cm, indicating its suitability for applications requiring specific dielectric properties.

This specific classification is a temporary measure, falling under Section XXII and Chapter 99, indicating its role within special or temporary tariff provisions, often related to trade agreements or import restrictions. Unlike the broader categories of raw materials or general chemicals found in earlier chapters, this code targets a precisely engineered material with very narrow technical tolerances. Its uniqueness lies in the combination of physical form (spherical micro-spheres), particle size distribution, and electrical properties, distinguishing it from generic silicon dioxide (e.g., sands or quartz) or amorphous silica that does not meet these exacting standards.

As this node is a leaf node within the HTS database, there are no further subcategories to delineate. The detailed specifications provided in the description serve as the sole criteria for classification under 9902.01.27. Therefore, any amorphous silicon dioxide not meeting *all* the stipulated parameters, including the mean particle size, uniformity coefficient, trace metal content, and specific electrical resistance, would not qualify for this particular tariff provision and would need to be classified under its appropriate primary HTS code, such as subheading 2811.22.10, as referenced in the description.