Collection:
Juneau—Douglas City Museum
Object ID:
2007.22.047AB
Accession#:
2007.22
Credit Line:
Transferred from the U.S. Bureau of Land Management.
Object Name:
Balance, Specific—gravity
Title:
Jolly Balance — Specific Gravity Scale
Year Range from:
1950
Year Range to:
1996
Description:
Specific gravity balance or "Jolly" balance.
Object's base is a tripod made from metal that has been painted black. On the leg directly under the balance mechanism is a manufacturers nameplate that says "Eberbach & Son CO." There are two poles coming out of the base, the largest one is in the center. Attached to this pole is a ruler that starts at zero at its top and goes to 40 at the bottom. This center pole has two extensions that nest into its center. The height of the pole can be adjusted with a knob at proper right. Attached to the top of this pole is a bracket with an eye hook that holds a spring. This spring has an open hook in its bottom that holds two dishes one over top of the second. The bottom dish is made our of plastic and is cracked in two places.
The second pole is mounted to the middle leg of the tripod. It holds two platforms that can be adjusted to move up and down. The bottom platform is designed to hold a beaker. The top platform has a small round mirror attached to it. This mirror has a line etched horizontally across it's center, and is used in adjusting the instrument.
Object's base is a tripod made from metal that has been painted black. On the leg directly under the balance mechanism is a manufacturers nameplate that says "Eberbach & Son CO." There are two poles coming out of the base, the largest one is in the center. Attached to this pole is a ruler that starts at zero at its top and goes to 40 at the bottom. This center pole has two extensions that nest into its center. The height of the pole can be adjusted with a knob at proper right. Attached to the top of this pole is a bracket with an eye hook that holds a spring. This spring has an open hook in its bottom that holds two dishes one over top of the second. The bottom dish is made our of plastic and is cracked in two places.
The second pole is mounted to the middle leg of the tripod. It holds two platforms that can be adjusted to move up and down. The bottom platform is designed to hold a beaker. The top platform has a small round mirror attached to it. This mirror has a line etched horizontally across it's center, and is used in adjusting the instrument.
Notes:
This objects was used to weigh things while suspended in a known volume of water. The additional mass and volume displacement of the sample could then be used to calculate the specific gravity of the sample. The amount that the length of the spring changes when a sample is weighed in air, and then in a liquid, is what the calculations are based on.
Search Terms:
JMIC
Assaying
T&E
Mining
Assaying
T&E
Mining
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2007.22.047
2007.22.047