D e p a r t m e n t of C h e m i s t r y , T h e O h i o S t a t e University, C o l u m b u s 10, O h i oA n apparatus and procedure for the quantitative semimicro-and microdetermination of methoxyl and ethoxyl groups i n acetals and easily volatile alcohols are described. A modified reaction flask, scrubber, and receiver are incorporated in the all-glass apparatus. Both solid and liquid samples are introduced below the surface of the reaction mixture by means of sealed containers. HE usual procedures for the determination of methoxyl or T ethoxyl groups (13, 15, 16, 21) give low results when applied to easily volatile substances or to relatively nonvolatile substances, such as alcoholates, acetals, or esters, which are rapidly hydrolyzed to easily volatile alcohols under the conditions of the analysis. The principal source of error in the determination has been attributed to the volatility of the lower alcohols, which tend to escape the reaction mixt'ure before being completely converted to the corresponding alkyl iodides. Discrepancies in methoxyl and ethoxyl analyses of volatile substances have often been noted (3, 6 , 7 , 9, 22) and the magnitude of the errors has been determined (3, 7 ) . Various modifications in apparatus and procedure have been proposed to correct this difficult,y.Shortly after the appearance of his original paper on the determination of methoxyl groups (21), Zeisel described a modification of his procedure applicable to volatile compounds (22). The substance to be analyzed was decomposed with hydriodic acid in a sealed tube at 130", cooled, and transferred to the reaction flask. The liberated alkyl iodide \vas then swept into a receiver containing an alcoholic solution of silver nitrate, after which the precipitated silver iodide was determined gravimetrically, as in the original procedure. The method has been used Figure 1. Apparatus for Determination of JIethoxyl and Ethoxyl Groups All dimensions in millimeters with some modification for the alkoxy1 analysis of such low boiling substances as methyl alcohol (22), ethyl ether (7, 19), and ethyl formate ( 7 ) .A second method of analysis, the so-called double distillation procedure, involves distillation of the alcohol (or corresponding alkyl iodide) from the substance being analyzed, into hot hydriodic acid, the remainder of the procedure being carried out' as in the gravimetric procedure of Zeisel or the more rapid volumetric procedures of Viebnck and eo-workers (15, 16). The double distillation procedure has been used for the determination of the lower alcohols in dilute aqueous solutions containing aldehydes ( I S ) , for the determination of the glycosidic methyl group in sugars (5), for the determination of acetals (6, 9, bo), and as one of several methods investigated t,o dekrmine their reliability in the methoxyl analysis of organic liquids (3). The results obtained with the double distillation procedure have not been altogether satisfactory and the apparatus is troublesome to operate.Herein is reported a modification of t,he vol...
