Procedure:

Typical experimental arrangement of radiometric titration consists of a titration vessel containing filter disc for phase separation as shown in Figure along with scintillation detector and lead shielding.  A syringe is used to move supernatant solution into and out of the counting chamber which may be a scintillation detector.

A typical example of radiometric titration is for the determination of halides using ¹¹⁰Ag (t_1/2 = 252 d) as tracer where corresponding silver halide is precipitated. In order to understand this method you may consider the titration of 10 mL of 1mM NaCl solution containing Cl^- with 1 mM solution of ¹¹⁰AgNO₃ to follow the reaction;

¹¹⁰AgNO₃    +             NaCl^-  →       ¹¹⁰AgCl (ppt) + NaNO₃

Figure: Illustration of experimental set-up for radiometric titration

where K_sp = 1.82 ×10^-10  for AgCl. Activity of the supernatant solution is monitored after equilibrium is attained following the addition of titrant. Initially solution containing NaCl has no activity. With the addition of increasing amount of ¹¹⁰AgNO₃, supernatant will have very little or insignificant activity because all the activity would have gone to the precipitate of ¹¹⁰AgCl. After the end point, however, activity of ¹¹⁰AgNO₃ will come into the solution and keep increasing with every additional drop. Titration data are plotted as shown in Figure from where equivalence point is the intercept of the two straight lines of the curve.