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Sperti Mercolite UV Suntanning 45QZ |
One of the difficulties of early mercury lamps was the ignition of the arc, and in 1940 Sperti patented the novel design featured here. The electrodes at each end of the tube consist of large diameter open coils of tungsten wire, each protecting an inner ceramic pellet coated on its outside with an oxide layer to improve thermionic emission. A heavy-gauge tungsten filament is wound through each pellet and connected directly between the two electrodes. When energised, the filament becomes incandescent and heats the pellets. After several seconds a glow discharge envelops each elecrode, gradually increasing in length along the tube until meeting at the centre. At that point the filament is short-circuited by the low impedance discharge, and ceases to have any further effect. The ultraviolet intensity gradually increases as the mercury vapour pressure rises.
The bulb is made of Corex glass, transmitting wavelengths down to about 300nm for an erythemal effect. It appears to be run close to its thermal limits, since the glass has become slightly deformed in the central region. It is belived to date to 1940 since the box bears the company's original name and address, which was vacated that year to move to larger premises along with a name change to Sperti Products.
| Manufacturer: | Science Laboratories Inc. | |
| Lamp Power: | 45 Watts? | |
| Lamp Current: | 2.8 Amps? | |
| Lamp Voltage: | 17 Volts? | |
| Cap Type: | E17 | Brass + vitrite |
| Bulb Type: | T-22.2 | T-7 in eighths/inch |
| Bulb Finish: | Clear | Corex Glass |
| Electrodes: | Oxide coated ceramic pellet inside metal coil | |
| Atmosphere: | Hg | Ar | |
| Luminous Flux: | lm | |
| Luminous Efficacy: | lm/W | |
| Radiant Flux: | UV-A W, UV-B W | Visible W |
| Colour Temperature & CRI: | CCT: K | CRI: Ra |
| Chromaticity Co-ordinates: | CCx: | CCy: |
| Rated Life: | Unknown | |
| Warm Up / Re-strike Time: | Approx. 10 minutes | Instant |
| Burning Position: | Universal | |
| Overall Length: | 146 mm | 53/4 inches |
| Light Centre Length: | 92 mm | 35/8 inches |
| Factory: | Cincinnati, OH | U.S.A. |
| Date of Manufacture: | Approx. 1940 | Date Code: 352A |
| Original Value: | Unknown | |
