Vol. 76
NOTES
4474
Additional evidence for reaction 1 is that the TABLE I El/, corresponds closely to those of chloral hyBUFFERSOLVTIOSS drate3a and trichloroacetaldehyde diethyl aceta13b Buffer Composition pH which are similar in structure to trichloroethanol. 1 0.5 M KCl with added HCl 2.2 Runs in 0.1 % ':I tetra-n-butylammonium iodide in 0.5 M NaOAc with added HOAc 2 4.9 677, methanol-water showed only one wave of 0.126 M Ka2HP04.12 H,O, 0.0368 .'IT 6.0 3 El:, of -1.67 v. over the potential range of 0 to citric acid monohydrate and 0.156 .IT -2.5 v. vs. S.C.E. Dichloro- and chloroethanol KC1 are probably reduced a t more negative potentials. 0.164 M NanHPO4.12 HnO, 0.017fj .\I 7 0 Acidic Nature of Trichloroethano1.-Ethanol in citric acid monohydrate, : L I I ~0 . 0 7 3 .lI aqueous solutions behaves as an extremely meal; KCl acid ; trichloroethanol, by analogy with the chloro0.194 M S a 2 H P 0 4 . 1 2I I ? O , 0.0028 .lf 8.0 acetic acids, would be expected to be a much citric acid monohydrate stronger acid. The El/, values (Fig. 1) seem to be 0.5 ,If r\",Cl with added SHa 4 8.3-9.6 independent of p H in a given buffer system up to 0.082 M SapB40,.10 H20and 0.320 J T 3 9.2 p H 10 or 11; a t higher pH, El/? shifts to more negaK C1 tive potentials. Accurate values could not 0.082 A f Na2B407.10HzO, 0.302 Jf KC1, 9.5 be determined a t pH higher than 12.4 due to interwith added NaOH ference from background discharge. Presumably, 0.082 di Sa2B407.10H1O, 0.285 .lIKCI, 9 8 if values in the higher pH region were known, an Swith added iTaOH type EI/,vs. pH curve would be obtained. c, 0.163 AI Sa.HP04.12 HzO w i t h :i(ldctl 10.3 Such S-shaped]relations,between pHIand El/, have NaOH been observed [for a variety of acidic compounds, 0.145 JI Na2HP04.12H 2 0 with :idtlt.tl 11.6 e.g., unsaturated] acids,4 2-haloalkanoic acids,'
