4 (since efficiencies are considered errorless), 4% lower at the tritium minimum and 1% lower at the carbon-14 minimum. Since the complete and simplified equations give curves so much alike in shape, it is often satisfactory to use the simplified equations, at least as a preliminary means of determining settings. If sample rates are large compared to background, and the background error contribution is minimized by a long counting time, Equations 27 and 28 can be further simplified by commission of the terms involving background. It then is a very simple matter to calculate relative error curves for different instrument settings.Ratios of Isotopes to Each Other. Equations 19 and 20 have been evaluated for many combinations of Cu/H3 ratios, ratios of Cu to background and sets of counting efficiencies. For a given C14/background ratio, the C14 error decreases as C14/H3 increases.The tritium error increases as C14/H3 increases. At some point the two errors are equal. This point occurs within the Cl4/H3 range 0.1 to 0.5 for a wide variety of conditions. As the C14/B ratio increases past 10, the errors decrease only very slightly within the C,4/H3 range 0.1 to 0.5.