Question

Holding the glass pipette in one hand and the forceps in the other, heat the bottom \(1 / 2-1\) inch of the pipette in the Bunsen burner until it becomes soft. Using the forceps, gently bend the soft glass tip approximately 45-90 degrees (1/8-1/4 turn). Do not clamp down on the glass with the forceps and do not attempt to bend it too far. Doing either will close the tip and make the pipette unusable.

Short answer

Heat the pipette in a flame, then gently bend the soft section with forceps to a 45-90 degree angle without clamping too hard or bending too far.

Step-by-step solution

Prepare Your Materials

Ensure you have the glass pipette, forceps, and Bunsen burner ready. Light the Bunsen burner and adjust it to a moderate flame.

Heat the Pipette

Hold the pipette securely with one hand and position the bottom 1/2-1 inch of the pipette into the blue part of the Bunsen burner flame. Rotate the pipette slowly to heat it evenly.

Check for Softness

Watch for the glass at the bottom of the pipette to become soft. This should take about 20-30 seconds. The glass will begin to glow a dull red, indicating it is soft and ready to bend.

Bend the Pipette

Use the forceps in your other hand to gently apply pressure to the soft section of the glass. Slowly bend it to a 45-90 degree angle, making sure not to clamp too hard. Rotate 1/8 to 1/4 turn as needed.

Cool the Pipette

Once bent, remove the pipette from the flame and hold it steady until the glass cools and hardens. Avoid touching the hot end until it cools completely.

Inspect the Pipette

Check the bent tip to ensure it is open and not closed or obstructed. The pipette should have a smooth, curved bend ready for use.

Key concepts

Bunsen burner flame

To start with the pipette bending technique, you need to use a Bunsen burner flame properly. The Bunsen burner creates a flame that can reach high temperatures, ideal for heating glass. It typically has two main parts: the inner blue cone and the outer luminous part. For this task, position the pipette in the blue part of the flame, where the temperature is highest and most stable. This part is called the 'hottest zone.' Ensuring a steady flame will help heat the glass evenly.

• Always adjust the flame to a moderate level; too high could be dangerous and too low might be ineffective.
• Remember to keep the working area clear of flammable materials to maintain safety.
• Proper lighting and adjustment of the flame are essential to achieving the perfect heating conditions for the glass.

Heating the pipette in this manner is crucial for the next steps, where you will soften and bend the glass.

glass softening

After setting up the Bunsen burner, the next step involves heating the glass pipette to soften it. This requires patience and attention. Hold the pipette over the flame, specifically at the tip, and let it heat evenly. The glass will start to glow a faint red, signaling it's soft enough. This indication usually happens within 20-30 seconds.

• Rotate the pipette slowly to ensure all sides heat evenly without any risk of overheating one part.
• Stay focused and never leave the glass unattended in the flame to avoid uneven softening or accidents.
• Avoid rushing the process; gentle and consistent heating ensures the glass doesn't become overly brittle.

Proper softening is fundamental for the bending process, ensuring the glass is in the right condition to be shaped without breaking.

forceps handling

Using forceps correctly is essential for bending the softened glass pipette. Choose a sturdy pair of forceps with a grip that feels comfortable in your hand. Do not clamp down too hard on the heated glass, as this can cause it to close off or crack. Instead, apply gentle and controlled pressure to bend the pipette tip to the desired angle, usually between 45 and 90 degrees.

• Maintain a firm yet gentle grip to control the pressure applied to the heated glass section.
• Rotate the pipette gradually, using 1/8 to 1/4 turns to achieve a smooth bend.
• Continuous practice handling forceps will improve your dexterity and precision in this delicate process.

Proper handling of forceps is necessary to make a functional and smoothly bent pipette.

pipette inspection

After bending the glass, it's crucial to inspect the finished pipette to ensure it is ready for use. Once the glass has cooled and hardened, check the tip thoroughly. Make sure it hasn't closed off during the bending process.

• Observe the bend for any irregularities or cracks that could affect functionality.
• Ensure there are no obstructions in the pipette tip, which could impede the flow of liquids.
• Testing the pipette with a small amount of liquid can help verify its usability and smooth operation.

Regularly inspecting pipettes after bending helps maintain quality and prevents errors during their actual usage in experiments.