Hollow cathode, or electrodeless discharge lamps for all ele- ments determined . ( c ) Furnace.— Programmable, or muffle furnace with thermostat maintaining 450 ± 25°C. If muffle furnace is used, a separate pre-ashing device is required. See ( d )–( h ). ( d ) Hotplate .—Withheatingcontrol,toheatup toabout300°C. ( e ) Lamp .—IR 250 W, fixed to a retort stand in a way that allows adjustment of the distance to the plate. ( f ) Ceramic plate .—eg, Desiccator plate on a low stand, with a diameter that suits the hot plate. ( g ) Glass cover .—eg, Crystallizing dish, 185 mm diameter, 100 mm height, to fit on ( f ) or equivalent. ( h ) Wash-bottle .—“Scrubber,” containing H 2 SO 4 for purifica- tion of air. See Figure 999.11 for assembly of items ( d )–( h ). ( i ) Quartz or platinum crucibles .—50–75 mL. ( j ) Polystyrene bottles .—With leak-proof closures, 100 mL. Carefully clean and rinse all glassware and plasticware with HNO 3 or HCl to avoid metal contamination. Cleaning procedure for glass and plasticware. —Acid solution: 500 mL concentrated HNO 3 , C ( c ) +4500 mL deionized water, C ( a ). Wash first with water and detergent. Rinse with tap water, followed by deionized water, thenwithdiluteacid.Finallyrinse4–5timeswithdeionizedwater.