For some nonaqueous solvents, the autoionization, if it occurs at all, must be to a degree so small that
virtually no ions are present. If the ion product constant for a solvent is as low as 10 40 , the concentration
of each ion would be 10 20 M. This can be put in perspective by considering 1 mole of the solvent
and realizing that out of 6.02 10 23 molecules of solvent, only about 1000 have undergone ionization.
The presence of a minute trace of impurity (it is very diffi cult to obtain completely anhydrous solvents)
would account for more ions by reaction than would be produced by autoionization. Therefore,
some alternative must exist that removes the necessity for assuming that autoionization occurs.
When FeCl 3 is placed in OPCl 3 , it can be shown by spectrophotometry that FeCl 4 is present. One way
this could occur is by ionization of the solvent,