Philora MA/V Medium Pressure Mercury Discharge

Although the first Philips mercury lamps were produced in the vast Emmasingel works in the centre of Eindhoven, Holland, it was not long before a second production site was established in Great Britain, at the company's works in Croydon. This would appear to have been done completely independently from Eindhoven, as was the case for sodium and other lamps made in the UK at the time, as its design bears little resemblance to the Dutch originals.

The arc tube itself is manufactured in aluminosilicate hard glass which has been mould-blown as a bulb, the moulding and glass flow lines clearly evident on the outer surface of the tube. There are substantial irregularities in its wall thickness and diameter, which varies by as much as 2mm along the tube length, and it is suspected that the glass is of Dutch origin. The glass made in UK by Osram and BTH Mazda of this era does not show such severe non-uniformity, and Philips is not believed to have ever established lamp glass production of its own in London.

The electrodes are heavy open-coil oxide coated assemblies with a great excess of emitter on their surfaces. They are of the backwound form, and are sealed through either end of the inner bulb with stout molybdenum wires. A third auxiliary ignition electrode is situated 3mm from the main electrode at the cap end of the lamp. Heat-reflective coatings of platinum are used behind the electrodes.

The outer jacket is made in soft soda-lime glass, again blown as a bulb rather than made from tubing. The marking stamp has been applied to the inner surface of this envelope for extra durability.
Manufacturer: Philips Lighting Ltd. Lamp No. 57101G
Lamp Power: 250 Watts
Lamp Current: 2.15 Amps
Lamp Voltage: 130 Volts
Cap Type: E40s/45 Brass + Vitrite
Bulb Finish: Clear Soda-lime soft glass
Bulb Type: T-51 T-16 in eighths/inch
Overall Length: 290 mm 11½ inches
Light Centre Length: 170 mm 6¾ inches
Arc Length: 120mm 4¾ inches
Electrodes: CCC-8 Triple coil Double carbonate emitter
Atmosphere: Inner: Hg | Ar (1 atm) Outer: Nitrogen
Luminous Flux: 8,250 lm VBU (average)
Luminous Efficacy: 33.0 lm/W VBU (average)
Colour Temperature & CRI: CCT: 5400K CRI: Ra 6
Chromaticity Co-ordinates: CCx: 0.337 CCy: 0.421
Burning Position: Vertical
Rated Lifetime: 6,000 hours (to 50% survival)
Warm-up & Re-strike Time: 4 minutes 15 minutes
Factory: Croydon, London Great Britain
Date of Manufacture: Circa 1945
Original & Present Value: Unknown