Medium Pressure Mercury HgH 1000

Early mercury lamps made by German Osram were split into two principal families. The HgH types employed an arc tube of hard glass, while the HgQ types made use of a quartz arc tube. These two categories are directly comparable with the British MA and MB types respectively.

It was furthermore customary in many parts of continental Europe to name lamps according to their output in dekalumens (1 dekalumen = 10 lumens). Thus this HgH 1000 lamp is a 10,000 lumen device, drawing some 265 watts. It was joined by the larger HgH 2000 (450W) and the smaller HgQ 300 (75W) and HgQ 500 (120W) types.

The arc tube here is fabricated from aluminosilicate glass that has been blown into a mould, to form the desired shape. The end sections around the electrodes are of reduced diameter, the purpose being to increase the temperature here slightly, and attain a faster run-up time than usual. Heat reflectors of platinum paint are applied behind the electrodes to provide extra thermal insulation. The electrodes take the form of open tungsten coils containing an emissive pellet - most likely of thorium oxide.

The end seals are of typical Osram style, found also in many of the spectral lamps having hard glass discharge tubes. Two molybdenum rods are first sealed into a graded sealing glass, and it is remarkable to note that the seal is made almost without oxide on the wire (the colour remains silvery). This assembly is then fused into the end of the arc tube. The arc tube is supported resiliently between a pair of spiral springs. Small ridges in the outer jacket keep these springs in place.
Manufacturer: Osram GmbH
Lamp Power: 265 Watts
Lamp Current: 2.7 Amps
Lamp Voltage: 125 Volts
Cap Type: E40s/45 Brass + Porcelain
Bulb Finish: Clear Borosilicate hard glass
Bulb Type: T-46 dimpled T-15 in eighths/inch
Overall Length: 285 mm 11¼ inches
Light Centre Length: 190 mm 7½ inches
Arc Length: 110mm 4⅜ inches
Electrodes: C-6 Open Coil Thoria pellet emitter
Atmosphere: Inner: Hg | Ar (1 atm) Outer: Nitrogen
Luminous Flux: 10,000 lm (@ 100 hours)
Luminous Efficacy: 37.7 lm/W (@ 100 hours)
Colour Temperature & CRI: CCT: 5400K CRI: Ra 6
Chromaticity Co-ordinates: CCx: 0.337 CCy: 0.421
Burning Position: Vertical ± 45°
Rated Lifetime: Not published
Warm-up & Re-strike Time: 5 minutes 5 minutes
Factory: Berlin-A Germany
Date of Manufacture: October 1945 Date Code: mT3
Original & Present Value: CH Fr 50,- (1937)
References: 1) Osram Quecksilber Dampflampen fur Wechselstrom, November 1937 (Bulletin 52, Osram AG, Zurich).