When the Constant Temperature D. C. Arc Method (1,2) was applied, following the procedure of Eichoft and Addink (3), to prism spectrographs not considered by these authors, distinct anomalies were found. The instruments in question were Soviet medium quartz prism ISP-22 and Soviet Littrow KSA-1 spectrographs. (For a brief description of these Russian instruments, see (4)). The conversion factors (C. F.) were found not to be constant over the wavelength range of 2500 to 3500 A, and the instruments behaved as if the conversion factor was a function of wavelength. Because both spectrographs were prism instruments one would expect the conversion factor to be equal to unity over the whole wavelength range being examined (3). However, it was experimentally shown that the conversion factor increased as the wavelengths became shorter.
M. Malinek, "Note on the Conversion Factor for the Constant Temperature D.C. Arc Method," Appl. Spectrosc. 16, 194-195 (1962)