The convex side of a curved crystal will diffract a continuous range of x-ray wavelengths simultaneously. Thus, it is useful for spectral analysis of flash x-ray tubes or plasmas where there is not sufficient time to scan through the spectrum with a spectrometer. It is also convenient for detecting impurities in x-ray targets and could be used for x-ray spectrochemical analysis. The choice of analyzing crystal, the particular diffracting planes, and the orientation of the bending axis allows a considerable versatility in intensity and dispersion including the recording of two or three separate spectra in a single exposure.