Ultra-Violet Radiation in Industry

Abstract

ON December 1 a small but interesting demonstration on ultra-violet radiation in industry was given by Hanovia, Ltd., at 3 Victoria Street, London, S.W.l. The demonstration was divided into three parts showing respectively: photochemical and photobiological reactions ; fluorescence and phosphorescence ; and a selection of ultra-violet lamps in stock and in current use. In the first section was illustrated the use of ultra-violet radiation for the production in a few hours or days of the effect of several years of bright sunlight, by which means the deterioration of dyes, paints, varnishes, metal surfaces, etc., can be rapidly tested. Other photochemical reactions included the polymerization of methyl methacry late for joining ‘Perspex’ sheets, the isomerization of ergosterol into calciferol (vitamin D2) and the application of ultra-violet for rapid photoprinting. The radiation is also used for its gerniicidal properties in sterilizing atmospheres and in the brewing, bottling and other food industries. Fuorescence of materials under ultra-violet radiation has many applications, such as the testing of fabrics (particularly for invisible oil-spots before dyeing), in forensic medicine and for partition chromatography. The addition of fluorescent tracers in plumbing systems, etc., for observing leaks and flows is of great importance, since the detection of one part in 108 can be achieved. Most of the above-mentioned work can be done with lamps of the extra-high pressure type (mercury-filled at pressures of 6,000-2,000 mm. of mercury) and high pressure type (2,000-600 mm.), the rays of which do not affect the skin or oyes and can be refracted by glass lenses and prisms. The spectrum for the high-pressure type is almost continuous at about 2800-3200 A., and the extra-high type is the same but with the wave-length energies displaced slightly towards the long end. For certain work, particularly for geological purposes, low-pressure discharge tubes (10-0·1 mm. pressure and almost monochromatic at 2537 A.) are used, and the radiation from these burns the skin and can only be refracted by quartz. Specimen lamps of all three types were shown, both mains-driven and battery-portables for field work being included.