As mentioned previously in Section 8.1, de Hevesy used the Pb-210 isotope in the first tracer experiments to determine the solubility of lead salts. Pb-210 has been used for self-diffusion studies of metallic lead, and the determination of exchange current density of lead amalgam.

As seen in Figure 4.4, Pb-210 is an intermediate member of the decay series of U-238, and it has a longer half-life (21.6 years) than the previous and the subsequent members of the U-238 decay series. Therefore, it has the tendency to accumulate and is considered as a polluting radioactive isotope in the environment. In some
places (e. g., Matraderecske, a village in Hungary), the atmospheric concentration of Ra-222, and simultaneously the concentration of Pb-210, is higher as usual. Since Pb-210 is formed as a result of alpha decays (see Figure 4.4) due to the recoil of the nucleus, Pb-210 can introduce into the glass plates of the pictures, photos on the walls of the houses in these places. If the age of the glass plates is known (e. g., photos were taken on special occasions such as a wedding), the change of the radon concentration in the house can be determined from the Pb-210 activity.

Pb-210 emits weak beta particles; recently, it usually has been measured by the liquid scintillation technique (see Section 14.2.1). Before the construction of liquid scintillation spectrometers, the weak beta radiation of Pb-210 was determined by measuring the activity of Bi-210, the daughter nuclide of Pb-210. Before the mea­surements, Pb-210 and Bi-210 were separated. The sample containing Pb-210 was covered by aluminum foil to absorb the weak beta particles. The daughter nuclide of Pb-210, Bi-210, however, emitted beta particles with higher energy, which can transmit through the aluminum foil. The accumulation of Bi-210 gives infor­mation on the activity of Pb-210. After reaching the secular equilibrium between Pb-210 and Bi-210 (which takes approximately 50 days), the activities become the same.