Mechanisms involved in iodination of salicylamide protocol
The order of events is probably:


  Protonation of the hypochlorite ion


$$\ce{ClO- + H3O+ &lt;=&gt; ClOH + H2O}$$


  Nucleophilic displacement of chloride by iodide


$$\ce{I- + ClOH \phantom{0}&lt;=&gt; Cl- + IOH}$$


  Protonation of hypoiodous acid


$$\phantom{000}\ce{IOH + H3O+ &lt;=&gt; IOH2+ + H2O}$$


  Fragmentation of the $\ce{IOH2+}$ cation


$$\phantom{00000}\ce{IOH2+ &lt;=&gt; I+ + H2O}$$

Alternatively, the second step could have been protonation of hyochlorous acid, followed by displacement of water by iodide, and then fragmentation of iodine monochloride:

$$
\begin{align}
\ce{ClOH + H3O+ &amp;&lt;=&gt; ClOH2+ + H2O}\\
\ce{I- + ClOH2+ &amp;&lt;=&gt; ICl + H2O}\\
\ce{ICl &amp;&lt;=&gt; I+ + Cl-}
\end{align}$$