2853 - Phosphides, whether or not chemically defined, excluding ferrophosphorous; other inorganic compounds (including distilled or conductivity water and water of similar purity); liquid air (whether or not rare gases have been removed); compressed air; amalgams, other than amalgams of precious metals:

This HTS category, 2853, encompasses a diverse group of inorganic chemical substances that do not fit into more specific preceding headings within Chapter 28. It includes phosphides of various elements (excluding ferrophosphorous), which are chemical compounds containing phosphorus. Also covered are other inorganic compounds such as distilled or conductivity water, and water of comparable purity, often used in specific industrial or scientific applications. Notably, this heading also includes liquid air (regardless of whether rare gases have been separated), compressed air, and amalgams of metals, with the exclusion of amalgams made with precious metals.

Unlike headings focused on specific chemical families or elements, 2853 serves as a residual category for inorganic compounds and specific air-related products. Its sibling categories at the Section VI, Chapter 28 level would typically cover more precisely defined chemical groups such as acids, bases, salts, oxides, or individual elements and their simpler compounds. The breadth of 2853 lies in its inclusion of substances like purified water and air mixtures, which have distinct physical properties and applications separate from typical chemical salts or oxides.

Within this heading, the subcategories further refine the classification. For example, 2853.10.00.00 specifically addresses cyanogen chloride, a distinct chemical compound. The remaining entries fall under the broader "Other" designation, indicating that subsequent subheadings will likely categorize the remaining diverse products based on their specific chemical nature or form, such as different types of inorganic compounds or amalgams not otherwise specified. This hierarchical structure ensures accurate tariff application by providing granular distinctions within the broad scope of this residual heading.