A search of the literature for data on the chromium content of the natural ruby revealed that none of the recorded analyses of ruby include this element; on the contrary, it has long been taken for granted that an attempt at such a determination is futile. Fremy,2 in writing about the ruby states that an analysis cannot show the real composition of the mineral; synthesis, however, serves to distinguish between essential and accessory constituents. This statement is a conclusion drawn from extensive experimentation, and forms the basis for the assertion that the color of naturally occurring ruby is due to chromium. Wohler and Kraatz-Koschlau3 found that chromium in natural ruby is present in amounts too small to be determined by analytical methods. Doelter4 also states that the chromium content of ruby is so small that it cannot be quantitatively determined. Doelter and Leitmeier5 say that only traces of chromium can be detected in ruby. It was, therefore, deemed expedient to find out whether an analytical method could be adapted to the determination of chromium in ruby.