Note-In general, individual nonmedicinal chemical elements and compounds are classified in Class 6810. Combinations (or mixtures) of chemical compounds, or chemicals prepared in a particular vehicle (other than water) are generally classified according to use, in classes other than 6810. For example, the chemical compound DDT, is classified in 6810, whereas DDT liquid spray, the insecticide, is classified in 6840-Pest Control Agents and Disinfectants. Similarly items of supply bearing nonchemical names such as BLEACH; INSECTICIDE, ROACH; and ANTIFREEZE are generally classified according to use, in classes other than 6810, whereas corresponding chemical compounds, such as sodium hypochlorite solution, chlordane, and ethylene glycol are classified in 6810. Medicinal chemicals are generally classified in 6505-Drugs and Biologicals; in vitro diagnostic substances and reagents are classified in 6550-In Vitro Diagnostic Substances, Reagents, Test Kits and Sets. Excluded from this group are liquid chemicals designed exclusively for use as propellant fuels and oxidizers.