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

The vessel is manufactured from Type I borosilicate glass, 3.3 mm wall thickness, offering linear thermal expansion 3.3 × 10⁻⁶ K⁻¹ and resistance to chemical attack by neutral and weakly acidic solutions. Overall height is 198 mm; external diameter is 54 mm. The cylindrical body terminates in a 60° conical shoulder leading to a neck of 18 mm internal diameter, ground to a 1:10 standard taper for an interchangeable glass stopper. The stopper is produced from the same borosilicate stock, lapped to Ra ≤ 0.5 µm, and is designed to achieve a seal leakage rate below 1 × 10⁻³ mbar L s⁻¹ when lightly greased.

A single circumferential graduation line is permanently etched 18 mm below the shoulder junction, indicating the 250 mL volume with ±1 mL tolerance at 20 °C. A 25 × 12 mm fused ceramic-enamel label field is provided on the upper shoulder for sample identification; the enamel withstands autoclaving at 121 °C and repeated exposure to dilute acids and bases.

The flat base incorporates a 4 mm central recess to seat a 35 mm magnetic stir bar and to prevent lateral displacement during titration. The underside is ring-reinforced to maintain vertical stability on level benches. The bottle is suitable for Winkler iodometric, membrane-electrode, or optical dissolved-oxygen determinations. Operating temperature range is 0 – 150 °C; maximum permissible thermal shock is ΔT 120 °C.

Cleaning protocol: rinse with 0.1 M hydrochloric acid followed by distilled water; alkaline detergents may be used at pH ≤ 10. Each unit is packed in a moulded pulp sleeve within a single-wall corrugated carton to prevent transit damage.