Low pressure sodium lamp, type Na-10

As knowledge of materials and experience making electric lamps grew in the early 20th century, more efficient light sources began to reach the market. In 1932 a collaboration of General Electric Company of England (GEC), Philips in the Netherlands, and Osram in Germany introduced a discharge lamp that used low-pressure sodium vapor. The key to a workable sodium lamp lay in a special glass (called borate glass) that could withstand the very corrosive nature of sodium. Arthur Compton in the U.S. described such a glass in 1926. But it took five more years to learn how to actually produce it so that a lamp could be made.
Discharge lamps make light by passing an electrical current through a gas, in this case sodium vapor. The current energizes the gas which then emits light. In this lamp, the sodium is contained by the bulb, which is lined with the borate glass. The lamp in turn is mounted inside a larger, double-walled glass jacket (part of the light fixture, not shown) to keep the temperature around the lamp stable during operation. Sodium light is a stark yellow suitable only for use in applications like street lighting, but the energy efficiency is very high. Early models gave 40 lumens per watt (lpw), a figure that reached about 100 lpw by 1960. Today's low-pressure sodium lamps give close to 200 lpw, the most energy efficient light source commercially available.
This lamp was made for street-lighting use by (U.S.) General Electric around 1940.
Lamp characteristics: Plastic, four-post base. Re-coiled tungsten electrodes mounted inside metal shields. The small brown cylinder mounted near the stem press is a starting resistance. Six asbestos insulator rings mount on the lamp's neck and are secured by the brass collar. (The rings have been removed and stored while the lamp is on display and are not in this picture.) Tipless, T-shaped envelope with about 70% of the inner wall coated by condensed sodium.
Currently not on view
date made
ca. 1940
Date made
ca 1940
General Electric Vapor Lamp Company
Physical Description
plastic (overall material)
glass (overall material)
sodium (overall material)
metal (overall material)
overall: 13 in x 3 in; 33.02 cm x 7.62 cm
ID Number
accession number
catalog number
Credit Line
from the Mt. Vernon Museum of Incandescent Lighting, thru Hugh F. Hicks
See more items in
Work and Industry: Electricity
Energy & Power
Data Source
National Museum of American History


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