3815.90.20.00 - Of mercury or of molybdenum

This HTS category, 3815.90.20.00, encompasses catalytic preparations, reaction initiators, and accelerators that are *not elsewhere specified or included* and consist *wholly of inorganic substances*. Specifically, this subheading designates such preparations when they are derived from or principally contain mercury or molybdenum. These substances are often utilized in industrial processes to facilitate or speed up chemical reactions, where their unique chemical properties make them effective catalysts.

Distinguishing this category from its siblings is crucial for accurate classification. While 3815.90.10.00 covers similar preparations based on bismuth, tungsten, or vanadium, this subheading focuses exclusively on those where mercury or molybdenum is the key inorganic component driving the catalytic or initiating activity. The difference lies solely in the specific elemental composition of the inorganic catalyst or accelerator.

As a leaf node within the HTS, 3815.90.20.00 does not have further subcategories. Therefore, classification under this heading relies on confirming that the product meets the criteria of a miscellaneous chemical preparation used as a catalyst or initiator, is composed entirely of inorganic substances, and its primary active components are mercury or molybdenum. Examples would include mercury oxides used as catalysts in certain organic syntheses or molybdenum disulfide employed as a solid lubricant and catalyst support.