The Purification of Water by Ultraviolet Radiation

Abstract

Little is known regarding the exact nature of radiant energy. It is quite certain, however, that radiant energy is propagated by wave motion. The fact that the waves are transmitted through a vacuum calls for a carrier. Scientists have for years regarded the ether as the medium by and through which these radiations are propagated. If a time should come when the hypothesis of an ether must be discarded, the change will not materially affect the properties and applications of ultraviolet energy. The human eye is capable of receiving and recording wave lengths of radiant energy that vary from 390 m/x to 770 m/*. The former figure2 is the value given for the wave length of visible violet light; the latter is for the wave length of the visible red. The wave length values for the other spectrum colors lie within these limits. Wave lengths of radiant energy that are shorter than 390 m/* are invisible. Ultraviolet radiation, with its arbitrary subdivisions, (near, intermediate and extreme) occupies this short wave length region of the spectral range of radiant energy. Since the velocity of radiant energy in space is approximately 3 X 1010 cm/sec, the frequencies may be calculated by dividing the velocity by the wave length. When, for example, the wave length is 400 m/i (the frontier of visible radiation) the frequency has the value 75 X 1013 per second. It follows that the frequencies of radiations in the ultraviolet are much higher, since the wave lengths in this region are shorter than 400 m/x. It may be said, then, that ultraviolet radiation is characterized by (1) invisibility, (2) short wave length, and (3) high frequencies. They are quite easily absorbed by matter. Relatively few substances allow the radiation to pass through them. Clear fused quartz,