PREPARATIONS 185 diazo solution. A vigorous reaction occurs, nitrogen being freely evolved, and some iodine being liberated owing to the slight excess of nitrous acid present. Allow the complete mixture to stand for 10 minutes with occasional shaking, and then heat it on a boiling water-bath for a further 20 minutes to complete the reaction: the crude iodobenzene separates as a heavy dark oil at the bottom of the flask. Add 10% sodium hydroxide solution to the mixture until the latter is definitely alkaline, i.e., until a drop withdrawn on a glass rod imparts a definite blue colour to red litmus-paper: this converts any phenol which may have been formed into sodium phenoxide which (unlike phenol itself) is not volatile in steam. Now equip the flask for steam-distillation (Fig. 15, p. 33), and steam-distil the mixture until no more oily drops of iodo-benzene come over with the aqueous distillate. Transfer the distillate to a separating-funnel, and carefully run off the heavy lower layer of iodobenzene into a small conical flask, rejecting the
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.