Burette with Straight Stopcock, Class B

A high-quality glass burette designed for volumetric analysis and titration. The "B" designation indicates it is a Class B instrument, which typically has a capacity tolerance twice that of Class A, making it ideal for routine laboratory work and educational demonstrations.

Key Features

• Material: Manufactured from Borosilicate 3.3 glass, providing superior thermal shock resistance and chemical durability.
• Stopcock Type: Features a straight-bore glass stopcock (1642B) or an interchangeable PTFE (Teflon) stopcock (1642A/TF) for smooth, leak-proof liquid control.
• Accuracy: Calibrated "To Deliver" (TD, Ex) at a standard temperature of 20°C.
• Standards Compliance: Manufactured in accordance with ISO 385 and DIN 12700 standards for volumetric glassware.
• Graduations: Includes permanent, high-contrast markings (Amber / Brown) that are easy to read against clear glass.
• Stopcock: Glass Stopcock

• Educational Training: Widely used in school laboratories for teaching acid-base titration techniques.
• Routine Analysis: Suitable for chemical controls in histology labs, buffer solution preparation, and standard solution titration.
• General Titration: Ideal for experiments where consistent, reliable results are needed without the cost of individually certified Class A glassware.

• Lubrication Required: Unlike self-lubricating PTFE, glass-on-glass joints require stopcock grease (often silicone-based) to ensure a vacuum-tight seal and smooth rotation.
• Risk of "Freezing": If left for long periods without cleaning—especially after use with alkaline solutions like sodium hydroxide—the glass key can "freeze" or permanently seize to the barrel.
• Chemical Limitations: While resistant to acids, glass stopcocks should generally not be used with strong bases for extended periods, as the alkali can etch the ground glass surfaces and cause the valve to stick.
• Fragility: Glass keys are more fragile than their plastic counterparts and can break or chip if dropped during cleaning or assembly.

• Superior Chemical Durability: Glass stopcocks offer universal resistance to almost all laboratory solvents and reagents. They are particularly well-suited for working with aggressive organic reagents or acids where polymer materials might swell or degrade.
• Precise Flow Control: When properly lubricated with stopcock grease, glass keys provide an exceptionally smooth action, allowing for highly controlled drop-by-drop delivery essential for accurate endpoint detection in titrations.
• Longer Service Life: Some technicians prefer glass for its potential for a longer life span compared to PTFE, provided it is handled carefully and cleaned regularly to prevent seizing.
• Cost-Effectiveness: Glass stopcock burettes are often more affordable than those equipped with high-quality PTFE valves, making them a standard choice for teaching laboratories and schools.

• Remove the Key: Gently pull the glass plug (key) out of the barrel. If it is already stuck, do not force it; apply gentle heat or a penetrating oil first.
• Dissolve Old Grease: Wipe away visible grease with a lint-free cloth. Use a small amount of solvent (like hexane, acetone, or warm soapy water) to dissolve stubborn residue from both the plug and the barrel.
• Dry Thoroughly: Ensure both the ground-glass surfaces are completely dry before applying new grease, as moisture will cause the grease to streak and leak. 

• Select the Right Grease: Use a high-quality silicone-based stopcock grease for general use, or a specialized hydrocarbon grease for high-vacuum applications.
• Apply Sparingly: Apply two thin longitudinal streaks of grease on opposite sides of the plug, away from the bore (the hole).
• Avoid the Bore: Never apply grease directly over or near the hole, as the pressure of insertion will force grease into the opening, clogging the burette tip. 

• Insert the Plug: Slide the plug back into the barrel.
• Distribute Grease: Rotate the plug repeatedly in one direction until the grease spreads evenly. The ground-glass interface should turn transparent and clear without any visible air bubbles or streaks.
• Check the Bore: Look through the hole to ensure no grease has migrated into the liquid path. If it has, disassemble and clean it again. 

• Short-term: Store the burette with the stopcock closed but the nut slightly loosened.
• Long-term: For storage exceeding a few weeks, remove the stopcock entirely or place a small strip of paper between the plug and the barrel to prevent the glass surfaces from fusing over time.