electrostatic analytical balance
Datecirca 1930
Inventory Number2006-1-0104
ClassificationAnalytical Balance
Subject
Maker
Empire Laboratory Supply Company, Inc.
ca. 1917 - 1939
Cultural Region
Place of Origin
Dimensions51 x 42 x 27.5 cm (20 1/16 x 16 9/16 x 10 13/16 in.)
Material
Accessoriessmall plastic box of weights; solid aluminum cyclinder marked "3"; large cyclinders (to be connected to power source and meter) (2); plexiglass stand for cylinders; sliding weights (2)
DescriptionStandard-looking wood and glass-enclosed two-pan analytical laboratory balance that has been retro-fitted by a user for the electrostatic measurement of mass by the replacement of one of the pans by a system of two metallic cylinders, one fixed to the floor of the case while the other hanging from the balance beam. It rests on leveling screws.
Pillar of balance is marked: "Prae [AS] cision / Germany". A modern notecard from inside the scale is marked: "Balances are very delicate and fragile! So handle most gently. Do not go "poking around" at balance parts." Another one on fiberboard base sheet is marked: "Turn voltage back to zero before snapping power off. Voltage may take ca 2 min. to come on. Measure diameters of cylinders on spare set (Do not take cylinders out from balance." Weight set inside balance is marked: "Physics 13b".
Pillar of balance is marked: "Prae [AS] cision / Germany". A modern notecard from inside the scale is marked: "Balances are very delicate and fragile! So handle most gently. Do not go "poking around" at balance parts." Another one on fiberboard base sheet is marked: "Turn voltage back to zero before snapping power off. Voltage may take ca 2 min. to come on. Measure diameters of cylinders on spare set (Do not take cylinders out from balance." Weight set inside balance is marked: "Physics 13b".
Signedon plaque: Empire Laboratory Supply Co. Inc. / Chemical & Bacteriological / Supplies / New York
FunctionThis balance works by the attraction that two oppositely charged metallic objects, in this case cylinders, exert on each other. If one connects each cylinder to opposite poles of a voltage source, they will after some time acquire a maximum charge with the effect of pulling the hanging cylinder downwards. This downward force depends on the applied voltage, so one can deduce the weight on the balance tray from the voltage one needs to apply to keep the system balanced.
The conversion of this balance to an electrostatic one seems to have been made for pedagogical purposes.
The conversion of this balance to an electrostatic one seems to have been made for pedagogical purposes.
Herman Kohlbusch Balance Company
Date: 1860-1880
Accessories: box of weights; accessories and spare parts for balance
Object number: 1998-1-1661
L. Oertling
Date: 1880-1940
Accessories: fitted wooden block with Eimer and Amend weights; two fitted boxes of weights (mahogany); simple wooden case of small weights with sliding top; weights stuffed in a cardboard box labelled "J.B. Prescott"; miscellaneous parts in a brown cardboard box; one brass dial knob; two identical brass pieces (red, black and brass) of unknown use; a round, flat glass tray that hangs from three strings; additional perforated pan with stirrup; two glass floats in a cardboard box; cylindrical float in a black cylindrical cardboard case; black tweezer; page from Gaertner Scientific Corp., page 4, "T1005. Analytical balance" now in instrument file folder (a different make and model); paper note with following note: Water dispat 60° / 12.3535
Object number: 1996-1-0412
Viard
Date: circa 1800
Accessories: Mahoghany box with five square brass weights (one missing) in box cut-outs, and nine small brass cutting weights inside sliding compartment
Object number: DW0985
French
Date: circa 1800
Accessories: Three nesting weights and ten small brass cutting weights
Object number: DW0984
Jean-Francois Wolschot
Date: date 1750
Accessories: square gold weights in box
Object number: DW0986
Christian Becker
Date: circa 1900
Accessories: in the drawer is a small box of weights, as well as two cards giving instructions for use
Object number: 2004-1-0308
Giellis Joerse
Date: 1634-1654
Accessories: square weights in box
Object number: DW0987
American
Date: mid 19th Century
Accessories: wooden, hinged box with hook closures and carved spaces for balance and weights; mall square weights in inner compartment of case; circular weights missing.
Object number: 1998-1-0041
Eimer & Amend
Date: circa 1922
Accessories: set-up instructions; weights; corked glass viles; tweezer; magnifying glass
Object number: 1996-1-0207
French
Date: circa 1880
Accessories: original wooden storage case with 2 cup weights (rest missing)
Object number: 1998-1-0173
James White
Date: circa 1895
Accessories: wooden case with weights (0298b)
Object number: 0298a
