Coloration of the Alkali Halides by X-rays

Coloration of alkali halides and other salts by x-rays.---(1) Hues produced. CsF, RbF, CaF₂, CsCl, RbCl, KCl, NaCl, LiCl, AgCl, BaCl, BeCl, CaCl₂, CsBr, RbBr, KBr, KI, NaI, CdI, HgI and K₂SiO₃ were colored, whereas KF, NaF, LiF, NaBr, RbI, ZnCl, NH₄Cl and about 20 other salts showed no coloration with 5 hours exposure to intense radiation. (2) Spectral absorption of colored halite and sylvite. Halite (NaCl), colored amber, has a broad absorption band from 0.3{μ} to 1.3{μ} with a maximum at 0.46{μ}. Sylvite (KCl), colored purple, has a similar absorption band with a maximum at 0.55{μ}. (3) Spectral fading of colored alkali chlorides. The colors fade logarithmically when exposed to daylight, the time varying from a few seconds to days. When exposed to the spectrum of a 500 watt Mazda Clamp, colored NaCl, KCl, RbCl and CsCl fade most rapidly at wave-lengths 0.51{μ}, 0.61{μ}, 0.68{μ} and 0.62{μ} respectively. When correction is made for the energy distribution, halite and sylvite are found to fade most rapidly at wave-lengths where their absorption increase due to their coloration is a maximum.