Philips Ultraphil MLU 300W Sun-Tanning
The Philips Biosol MLU (Mixed Light Ultraviolet) appears to have been introduced around 1950, at first in the powerful MLU 500W model. By 1951 that had been joined by the smaller Biosol MLU 250W with fixed series filament and arc, which was itself quickly superseded by this Ultraphil 300W model. It is not known why the power rating was changed, but it may have been simply to compete with the popular Osram Ultra-Vitalux which was also rated 300W. The MLU 300W was on sale at least as early as 1955, possibly as early as 1952 when the Ultraphil brand name was registered.

The arc tube operates at 125W and is of a standard pinch-sealed quartz design, but features additional platinum heat reflectors around its ends. It is connected in series with a tungsten ballast filament that dissipates 175W, and is loaded rather higher than in conventional mercury-blended lamps. This serves to decrease its peak wavelength for deeper penetration into human tissue, a similar principal as used for the matching Philips Infraphil heat lamps. This also limits the useful lamp life to about 1000 hours.

The bulb is blown in Philips 725 or Corning 7760 hard glass, a necessity due to the high power of this compact lamp. Its transmission curve extends slightly into the UV-C region, which is now known to be somewhat carcinogenic. The Philips MLU lamps were discontinued in the early 1980s when the use of this kind of lamp for personal tanning was banned in many European countries, owing to the powerful output and frequent ocurrence of erythemal burns. It was superseded by somewhat safer systems based on lamps having better filters to remove the shortest wavelengths, or using lower power density fluorescent tanning tubes.
Manufacturer: Philips Lighting Type 57265F/28
Lamp Power: 300 Watts 125W arc, 175W coil
Lamp Current: 1.34 Amps
Lamp Voltage: 220-240 Volts
Cap Type: B22d-3/25x26 Ni plated brass
Bulb Type: R-125 R-40 (in eighths/inch)
Bulb Finish: Inside Frosted Philips #725 hardglass
Electrodes: Backwound Tungsten BCY emitter
Electrode gap: 35mm Quartz ID: 10.0mm
Atmosphere: Ar | Hg (5 bar) Outer: Argon-Nitrogen
Luminous Flux: 4600 lm (21 UV Finsens)
Luminous Efficacy: 15.3 lm/W
Colour Temperature & CRI: CCT: 5100K CRI: Ra25
Chromaticity Co-ordinates: CCx: 0.345 CCy: 0.385
Irradiance @ 50cm: UV-A: 16.6W/m² -- UV-B: 8.8W/m² -- UV-C: 0.11W/m²
Beam Distribution 90° to half peak intensity
Rated Lifetime: 1,000 hours
Warm-up & Re-strike Time: 3 minutes 5 minutes
Burning Position: Universal
Overall Length: 174 mm 67/8 inches
Factory: Eindhoven The Netherlands
Date of Manufacture: 1968 October Date Code: K8
Original Value: DM 42/- 1966
References: 1) Philips Lighting Catalogue, 1965 International, p.113
2) Philips Lighting Catalogue, 1982 UK, pp.393-394 (last known listing)
3) Philips Preisliste Spezialentladungslampen und Infrarotstrahler, 1966 Germany, May, p.6
4) Fifty Years of the High Pressure Mercury Vapour Lamp, W.Elenbaas, Philips Technical Review v.18 no.6 (1956/57) pp.167-172
5) The High Pressure Mecury Vapour Lamp, W.Elenbaas, publ. Philips Technical Library 1965, pp.216-220
6) Gas Discharge Lamps, J.Funke & P.J.Oranje, publ. Philips Technical Library 1951, pp.140-141
7) Philips Training Manual MTO Turnhoutlampen, Hogedruk-Kwiklampen, Van der Stap & Goethals, 1986, p.28
8) Philips Ultraphil Trademark Registration, 09-X-1952, IP Australia website
9) Philips Biosol Advert, Dagblad De Stem 19th March 1955 p.10 (listing MLU 500W and 250W models)
10) Philips Biosol Advert, Dagblad De Stem 5th November 1956 p.8 (listing MLU 500W and new 300W version)
11) Philips Biosol Advert, Nieuwe Leidische Courant 4th December 1956 p.8 (listing MLU 500W and new 300W version)