Dissolved-oxygen bottle, brown glass, nominal capacity 250 mL.

The vessel is blown from Type III soda-lime glass containing approximately 2 % iron oxide, resulting in a uniform amber tint. Spectral transmittance at 450 nm is < 0.01 %, meeting the requirement for light-sensitive Winkler determinations. Wall thickness is 9.5 ± 0.5 mm, providing adequate mechanical strength for routine laboratory use without excessive mass. External diameter is 54 mm; overall height is 198 mm. The cylindrical body merges into a 60° conical shoulder that narrows to a neck of 18 mm internal diameter, ground to a 1:10 standard taper for a precision glass stopper.

The stopper is manufactured from the same amber glass and is matched to each bottle. The ground joint exhibits a surface roughness Ra ≤ 0.5 µm, yielding a typical leakage rate below 1 × 10⁻³ mbar L s⁻¹ at 20 °C when greased with a thin film of silicone or Apiezon L. A 25 × 12 mm ceramic enamel label patch is fused to the upper shoulder; the patch accepts graphite, wax pencil, or solvent-resistant marker and withstands repeated autoclaving at 121 °C without crazing or colour shift.

A single circumferential graduation line is etched 18 mm below the neck–body junction, marking the 250 mL volume to within ±1 mL at 20 °C. The base incorporates a shallow 4 mm central recess that centres the bottle on a standard 35 mm magnetic stirrer bar and reduces lateral movement during titration. The underside is ring-reinforced to minimize wobble on flat benches.

Operating temperature range is 0 – 60 °C; maximum permissible thermal shock is ΔT 80 °C. Cleaning: rinse with 1 % hydrochloric acid followed by copious distilled water; alkaline detergents may be used provided pH does not exceed 10. Suitable for Winkler iodometric, membrane-electrode, or optical dissolved-oxygen procedures. Each bottle is packaged in a moulded pulp sleeve within a single-wall corrugated carton.