184 PRACTICAL ORGANIC CHEMISTRY it is better to use sodium nitrite* of good quality and to add an amount which is about 10% in excess of that theoretically required. The student is recommended to carry out the preparation of iodo-benzene in order to gain experience in the preparation of aqueous solutions of diazonium compounds, and then to prepare a solution of benzenediazonium hydrogen sulphate with which to carry out the chief reactions that diazonium compounds undergo. lodobenzene. C 6 H 6 L When potassium iodide or hydrogen iodide is added to an aqueous solution of a diazonium salt, nitrogen is readily evolved (no catalyst being necessary) and the corresponding iodo-compound is formed. lodo-compounds can thus C 6 H 6 NjCl + KI = C 6 H 6 I + N, + KCl be readily obtained from aromatic primary amines. Required: Aniline, 15 ml.; hydrochloric acid, 40 ml.; sodium nitrite, 12*5 g.; potassium iodide, 35 g. Dissolve 15 ml. (15*4 g.) of aniline in a mixture of 40 ml.
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