QUANTITATIVE ANALYSIS 451 i. DETERMINATION OF NUMBER OF HYDROXYL GROUPS IN PHENOL. C 6 H 5 OH. Molecular Weight, 94. Prepare the acetylating mixture by adding i volume of acetic anhy-dride to 4 volumes of pure anhydrous pyridine, and shaking thoroughly. Immediately before use, transfer the mixture to a clean dry burette having a well-fitting glass tap, and then close the top of the burette by means of a soda-lime tube. Fit two similar ioo ml. conical flasks, A and B, with reflux water-condensers, using ground-glass joints or rubber stoppers. Connect up the water-condensers in series. Weigh the flask A, add about i g. of pure dry powdered phenol and weigh again. Now add io ml. of the acetylating mixture to the flask A, and also to the control flask B. Con-nect the flasks to the reflux condensers and heat both flasks on briskly boiling water-baths for 30 minutes. Then remove the water-baths, and pour 20 ml. of distilled water down each condenser, shaking the contents of each flask gently to ensure complete hydrolysis of the unchanged
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