## Weighing Techniques

1. Toploader
• Direct Weighing
1. With nothing on the pan, set to zero by pressing the "on" button.
2. Place weighing bottle, beaker, or vial on balance and set to zero again.
3. Use a clean scoopula to transfer sample into container slowly, until you reach the desired mass.
• Indirect weighing (Weighing by difference)
1. Place enough of the sample in a weighing bottle, put the lid on, and place on the scale. Record the mass.
2. Take some out and place it in a different container (whatever you will be using for the experiment). Record the new mass.The difference in mass is the mass of the sample transferred.
3. Continue this procedure until you have as much sample as you need.
4. It is best to transfer small amounts at a time, so you do not take more than you need. You should not put excess sample back into the weighing bottle.

Figure 1. A toploading balance

Figure 2. An analytical balance

2. Analytical Balance
• Use the same procedure as with a toploader, remembering these additional points:
1. Close all the doors before taking measurements.
2. Remember the number of significant figures. It is higher than on a regular toploader.

Make sure the sample is completely cooled when weighing. If a sample is still warm, it will weigh less because of buoyancy due to upward circulation of hot air.

For example, a 50 mL beaker 3 minutes after removal from a 110 degree oven weighs 27.0271 g. At room temperature, it weighs 27.0410 g.