In the complex, ${\mathrm{CoCl}}_3. 5{\mathrm{NH}}_3$, the number of ionizable chloride ions are

According to Werner's theory, primary valency of a metal is satisfied by negative ions only.

Werner formula …${\mathrm{CoCl}}_3. 5{\mathrm{NH}}_3$

Modern formula . . .$\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_5\mathrm{Cl}\right]{\mathrm{Cl}}_2\rightleftharpoons {\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_5{\mathrm{Cl}}_{ }\right]}^{2-}+2{\mathrm{Cl}}^{-}$

One chloride ion satisfies both primary and secondary valency…..dual character 

Two chloride ions satisfy primary valency only…..ionizable chloride ions

Five ammonia molecules satisfy secondary valency only.