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ANALYTICAL CHEMISTRY, VOL. 54, NO. 2, FEBRUARY 1982
Table I. Results of Determinations of Sulfonyl Chlorides by Reaction with 3-Chloroaniline mean purity found, std dev, compound %m/ma % methanesulfonyl chloride benzenesulfonyl chloride 4-toluenesulfonyl chloride 4-methoxybenzenesulfonyl
chloride 2,4,5-trichlorobenzenesulfonyl chloride a
99.0 99.4 99.2 99.4
0.20 0.15 0.29
98.9
0.17
0.23
Mean of five determnations.
purpose of maintaining the solution at 15 "C (5),of eliminating any vortex in stirring the solution, and in introducing the NaNOz titrant subsurface. Uptake of titrant is rapid at the beginning of the titration (110 mL/min) and diminishes slowly as the concentration of undiazotized 3-chloroaniline falls. Approach of the end point is made evident by increasing spikes in the potential readings immediately following incremental volume additions. At approximately 0.5 mL before the end point, incremental volumes of 0.05 mL should be dispensed every 20 s and at 0.2 mL before end point only every 30-45 8. Interferences. Additions of up to 10% of the corresponding sulfonic acids to the samples did not affect their determinations. Addition of dry HCl in conjunction with sulfonic acids was not studied but low levels of HCl were thought an unlikely interference since it is liberated during
sulfanilide formation. With some of the sulfonyl chlorides hydrolysis by water competed with sulfanilide formation and caused lower results to be obtained. Addition of 6 mequiv of water to 20 mequiv samples of methanesulfonyl chloride lowered its results by 0.8%. The same addition of water to benzenesulfonyl chloride had no effect. Extension of the Method. Within our laboratory, determinations of other sulfonyl chlorides have shown precisions equal to those shown in Table I. Although less convenient for our general use, trial determinations with samples of only 2 mequiv size indicate that the method can be scaled down to the measures described here. We have found that the method can be similarly applied for determining acid chlorides. Generally, as reported by Stahl and Siggia (6),the greater reactivity of acid chlorides allows for their complete conversion to anilides within 5 min at room temperature. Both NMP and dioxane have been used as solvents. LITERATURE CITED (1) Ashworth, M. R. F. "The Determination of Sulfur-Containing Groups"; Academic Press: London, 1972; Vol. I , Chapter 3. (2) Oribova, E. A.; Dyatiova, V. V.; Sterllna, L. I. Zavod. Lab. 1960, 46, 597-598. (3) Calcott, W. S.; English, F. L.; Wilber, 0. C. Ind. Eng. Chem. 1925, 17, 942-944. (4) Liiinenko, L. M.; Aleksandrova, D. M.; Napadaiio, V. G. Zh. Anal. Khlm. 1961, 16, 226-228. (5) Wolthuis, Enno; Kolk, Stephan; Schaap, Luke Anal. Chem. 1954, 26, 1238- 1240. (6) Stahi, Clarence R.; Siggia, Sidney Anal. Chem. 1956, 28, 1971-1973.
RECEIVED for review September 16,1981. Accepted November 16, 1981.
CORRECTIONS Isotopic Determination of Uranium in Picomole and Subpicomole Quantities
J. H. Chen and G. J. Wasserburg (Anal. Chem. 1981,53, 2060-2067). There is an unfortunate omission in the address of the place of work as given on page 2060. The complete address should read Lunatic Asylum, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125.
Explicit Finite Difference Method in Simulating Electrode Processes Renato Seeber and Stefan0 Stefani (Anal. Chem. 1981,53, 1011-1016). In the listings of the computer programs made available as Supplementary Material, the constant RATEHS has to be redefined as follows: RATEHS = RATEHS*DBLE(DELTAR/DELTAT) Moreover, in the simulating of a chronoamperometric test (uncomplicated charge transfer) the exact definition of SF1 is SF1 = SQPI/ (SQRT(SNGL (AA))*UZERO(1)) Finally, if CAPPA is the chemical kinetic constant RATECK = CAPPA*DELTAT
