S-2 Sunlight Mercury Discharge

In 1929 GE introduced the first succesful ultraviolet lamp, the S-1 Sunlight. It had been conceived by Royal Strickland and Matthew Luckiesh to deliver a spectrum having a mild ultraviolet content resembling that of the sun. It was believed that irradiating people with this light would give them vitality and maintain health.

The S-1 was a large 400W source for general irradiation in public areas, and a smaller domestic source was soon in demand for residential use. Thus in 1937, this 130W S-2 variant was launched. Initially it had a clear glass bulb, but owing to its uses at short ranges its high brightness produced too much glare. From 1939 onwards both this and the larger S-1 were only made with inside frosted pearl bulb.

It is a most unusual kind of hybrid incandescent-discharge lamp. The bulb is is of a special UV-transmitting hard glass, and is filled with an enormous quantity of mercury plus low pressure argon. It contains a V-shaped tungsten filament, whose ends have extra windings to increase their thermal mass such that they can function as electrodes. When illuminated on a low voltage transformer, the filament lights and thermionic emission takes place. As the mercury begins to vaporise a glow discharge is formed, which gradually transforms into an arc across the ends of the filament, ballasted by the transformer. The filament continues to decrease in intensity as the arc draws more current, but remains lighted at all times. It produces a warm white light plus infrared radiation, while the mercury arc contributes ultraviolet rays. The lower power of this S-2 lamp required the addition of the metal cap, to raise the temperature of the mercury pool and increase the UV output.
Manufacturer: General Electric Co. of U.S.A.
Lamp Power: 130 Watts
Lamp Current: 8.5 Amps 2A at starting
Lamp Voltage: 15 Volts 30V at starting
Cap: E29s/30 Admedium Brass
Bulb Finish: Clear hard glass Transmitting to 280nm
Bulb Type: PS-54 PS-17 (in eighths/inch)
Overall Length: 122.5 mm 4 7/8 inches
Light Centre Length: 95.25 mm 3 3/4 inches
Filament: C-2V Overwound plugged tails
Atmosphere: Argon 0.9 atm. during operation
Luminous Flux: 1,600 lm @ 100 hours
Luminous Efficacy: 12.3 lm/W @ 100 hours
Total Ultraviolet Output: 8,000 E-Vitons
Burning Position: Vertical base up to horizontal
Rated Life: 300 hours
Warm Up / Re-strike Time: 8 minutes to full UV output Instantaneous restrike
Factory: Nela Park, Ohio U.S.A.
Date of Manufacture: December 1939
Original / Present Value: Not Known
References: 1) GE Lamp Catalogue, USA, 1937, p.27
2) Weitz, C.E., GE-Mazda Lamps - Characteristics & App. lications (Bulletin LD-1) , General Electric U.S.A., 1939.
3) Biography of Royal Strickland
4) Biography of Matthew Luckiesh
5) US Patent 2,047,042 - Enclosed Arc Device, R.F.Strickland (General Electric USA>, Filed 1929-Nov-18
6) US Patent 2,081,776 - Enclosed Arc Device having improved electrodes (S-2), R.F.Strickland (General Electric USA), Filed 1931-May-19
7) US Patent 2,104,680 - Enclosed Arc Device having improved UV flux and starting, R.F.Strickland (General Electric USA), Filed 1931-Feb-25