The photochemical decomposition of (NH4)2TcCl6 in dilute HCl, HClO4 and H2SO4 solutions has been studied. Electrophoresis and spectrophotometry were used to identify TcCl
, TcCl5 (H2O)−, cationic and uncharged species and TcO
. The yield of each species as a function of the time of uv irradiation was determined. The TcCl
, yield decreases to zero after 50 h of irradiation. The TcCl5(H2O)−, cationic and uncharged species and TcO
are formed in different proportions in the three acids. After 120 h of irradiation of the HCl solution the principal Tc species
was the cationic one (≈70%) followed by the uncharged species (≈24%). In HClO4 solution the cationic species (≈70%) was followed by TcO
, but in H2SO4 solution the uncharged species amounts to ≈90%.