Balances can be classified in several different ways.

1. Precision of measurement.
   • Regular balances weigh to 1, .1, .01 or .001 g (1 milligram)
   • Analytical Balance, weighs to .0001 g . This is 0.1 mg.
   • Semi-micro and micro balances, weigh to .00001 and .000001 g . This is .01 mg and .001 mg or 1mg (microgram).
2. Mode of operation.
   • Mechanical....  Uses weights to balance object being weighed
   • Electronic...... Uses an electrical current to balance object

In this course, you will use four different types of balances:

Triple Beam Balance

1. Use for "crude" weighings.
2. This is a very sturdy balance. Never-the-less, clean up any spills!
3. Reset weights to 0.00  when finished.
4. At best this will weigh to .01 g.

Electronic Balances

1. State of the art balances.
2. Object to be weighed is counterbalances by a magnetic field generaled by an electrical current.
3. In General Chemistry Laboratory, use only when allowed 
4. These are fast.
5. These are accurate.
6. These are almost "idiot proof" !
7. They are frequently more expensive than mechanical balances.
8. In this course these will be used only for special experiments.
   In industry, where time is money, they are used almost exclusively.

Mechanical Analytical Balance.

1. Obsolete!!   Used only in special experiments.
2. Works like a teeter tauter, more or less!
3. Always shut off the balance before putting anything on or off an mechanical analytical balance.
4. Never lean on the bench when using an analytical balance.
5. Treat the balance gently. It is very accurate but also sensitive and somewhat fragile.
6. Before you leave an Analytical balance, make sure it is shut off and spotlessly clean!

© RWK 2004