SOME NEW STABLE ULTRAVIOLET TRANSMITTING SOLUTION FILTERS

Abstract

Abstract— For use with very intense light source, e.g. flash lamps and high‐pressure arcs, some new stable transmission filters for the U.V. were developed. All filters were composed to give maximum transmittance in the desired bands together with optimum absorbance of the visible light, at an optical path of 1 cm. The filters described are easy to prepare and have considerably better properties than the well known NiSO 4 ‐ ‐ CoSO 4 filter and other filter combinations. During initial irradiation with high‐intensity light sources the transmittance of the freshly prepared filter solutions increases slowly till maximum transmittance is attained. The position of the transmission bands, however, does not change. Based on the fact that the 6700 Å absorption band of some non‐aqueous solutions of CoCl 2 has an extinction coefficient about a hundred times larger than the 5100 Å absorption band of the aqueous solution with the same concentration, filter solutions were developed for the following transmission bands: 2600–3900 Å, 2900–3900 Å and 3100–3900 Å with transmission maxima of 90, 90 and 75 per cent respectively, and 2600–4600 Å, 2900–4500 Å and 3100–4600 Å with transmission maxima of 95, 95 and 90 per cent respectively, at an optical path of 1 cm.