Using the Analytical Balance in the Laboratory

A successful laboratory experience in this class requires your attention towards careful measurements that are both accurate and precise. The analytical balance lies at the heart of most of the measurements you make this semester, so it is important that you use and maintain the balances in lab correctly. Your accuracy and precision will greatly improve if you consistently follow the procedure outlined below every time you use the balance.

Before weighing

1. Make sure to remove all objects from the shelf on which the balance is placed. Never lean on the surface of these shelves while using the balance. Small changes in the level angle (even 1/10th of a degree) will decrease the accuracy of the measurement.
2. Inspect the surface of the pan area of the balance. Use a brush to clean off any chemicals and dust from the pan area. Report excessive spills to your TA.
3. Calibrate AND tare the balance before each weighing—especially if you need complete accuracy.
4. Make sure that all the doors of the balance are securely closed.

While weighing

1. Place the sample on the center of the scale.
2. Wait for a stable reading before recording a weight. This could take up to 20 seconds.
   • Note: An indicator circle appears on the bottom left of the readout while the balance is stabilizing. This indicator circle goes away once the reading has stabilized.
   • High accuracy measurements require an average. For these types of measurements, weigh your sample three times.
3. If you find your balance is drifting in a constant direction, try discharging the pan area using a kimwipe dampened with just a little DI water. Wipe down all the metal, including the splash plate. Give the balance a few minutes to dry off and try the measurement again. Static is often a problem when the air is dry, especially during the winter months.

After weighing

1. Use a brush to clean up any spills you make on the balances. Report excessive spills to your TA. Remember, excessive chemical spills are corrosive to the balance and can be dangerous to you.
2. Close all glass windows, including the one on the top of the balance. Leave the balance in good working condition for the NEXT student who will be using it.