The dissolving in hydrochloric acid is easiest, due to complex formation of TlCl4(-). In nitric acid and perchloric acid you get free Tl(3+) ions, but
these are VERY prone to hydrolysis to hydrous Tl2O3 and that makes dissolving Tl2O3 in one of these acids so hard. But for sure, dissolving in 20%
HNO3 or so works, albeit slowly.
|