The total rate of a nuclear transition which proceeds partially by internal conversion may be expected to change when alterations are produced in the states of the electrons concerned. Such alterations may be produced, for instance, by chemical means. Differences in the decay constant of the highly converted isomeric transitions of Te125m have been measured using Te, TeO2, and Ag2Te (synthetic hessite). The results are: λ(Te)-λ(Ag2Te)=(2.59+/-0.18)×10- 4λ(Te) λ(TeO2)- λ(Ag2Te)=(2.23+/-0.18)×10- 4λ(Te) λ(Te)-λ(TeO2)=(0.36+/-0.17)×10- 4λ(Te). The errors are standard deviations arising mainly from the statistical fluctuations of the number of ionizing events which contributed to a measurement by the double-ionization-chamber balance method. The ionization currents were produced by the K x rays following the internal conversion process in the sources. Corrections were made for the effect of an initial 0.05% contamination of Te123m. Sources of errors are considered in detail.