Phenyldiazonium hydrogen sulphate

When an aqueous solution of phenyldiazonium chloride or of p-tolyl-diazonium hydrogen sulphate is treated with an equivalent of potassium iodide and warmed on a water bath, iodobenzene or />-iodotoluene is formed in good 3deld ... 

To prepare the solid phenyldiazonium chloride or sulphate, the reaction is conducted in the absence of water as far as possible. Thus the source of nitrous acid is one of its organic esters (e.g., amyl nitrite) and a solution of hydrogen chloride gas in absolute alcohol upon the addition of ether only the diazonium salt is precipitated as a crystalline solid, for example ... 

---