[TiCp2(NCCH3)2] + can be used as a colorimetric indicator for oxygen contamination in inert-atmosphere glove boxes. Small quantities of the blue solution are conveniently prepared by dissolving small (mg) amounts of TiCp2Cl2 in acetonitrile in a scintillation vial, adding zinc dust, and capping. Aliquots of this solution may be removed by disposable pipet and transferred to an open vial. Inspection of the aliquot gives a qualitative indication of the dioxygen level in the glove box. As the solution is exposed to trace O2 the solution color changes from blue to green and ultimately, under higher dioxygen concentrations, to yellow.