The statements and rules of procedure which follow are sufficient for the intelligent use of an analytical balance in connection with processes prescribed in this introductory manual.  It is, however, imperative that the student should make himself familiar with these essential features of the balance, and its use.  He should fully realize that the analytical balance is a delicate instrument which will render excellent service under careful treatment, but such treatment is an essential condition if its accuracy is to be depended upon.  He should also understand that no set of rules, however complete, can do away with the necessity for a sense of personal responsibility, since by carelessness he can render inaccurate not only his own analyses, but those of all other students using the same balance.

Before making any weighings the student should seat himself before a balance and observe the following details of construction: 

1.  The balance case is mounted on three brass legs, which should preferably rest in glass cups, backed with rubber to prevent slipping.  The front legs are adjustable as to height and are used to level the balance case; the rear leg is of permanent length.

2.  The front of the case may be raised to give access to the balance.  In some makes doors are provided also at the ends of the balance case.

3.  The balance beam is mounted upon an upright in the center of the case on the top of which is an inlaid agate plate.  To the center of the beam there is attached a steel or agate knife-edge on which the beam oscillates when it rests on the agate plate.

4.  The balance beam, extending to the right and left, is graduated along its upper edge, usually on both sides, and has at its extremities two agate or steel knife-edges from which are suspended stirrups.  Each of these stirrups has an agate plate which, when the balance is in action, rests upon the corresponding knife-edge of the beam.  The balance pans are suspended from the stirrups.

5.  A pointer is attached to the center of the beam, and as the beam oscillates this pointer moves in front of a scale near the base of the post.

6.  At the base of the post, usually in the rear, is a spirit-level.

7.  Within the upright is a mechanism, controlled by a knob at the front of the balance case, which is so arranged as to raise the entire beam slightly above the level at which the knife-edges are in contact with the agate plates.  When the balance is not in use the beam must be supported by this device since, otherwise, the constant jarring to which a balance is inevitably subjected, will soon dull the knife-edges, and lessen the sensitiveness of the balance.

8.  A small weight, or bob, is attached to the pointer (or sometimes to the beam) by which the center of gravity of the beam and its attachments may be regulated.  The center of gravity must lie very slightly below the level of the agate plates to secure the desired sensitiveness of the balance.  This is provided for when the balance is set up and very rarely requires alteration.  The student should never attempt to change this adjustment.