of the stock solution of that metal were titrated to evaluate the precision of the method. These datit are presented in Table I. For comparison, titration data for silver and ammonium ions are also given. Typical “S’ shaped titration curves mere obtained throughout. Attempts were m2,de to titrate mixtures of various alkali metals. The resulting titration cur’res showed only a single inflection corresponding to the total amount of alkali metals taken. I n this respect, the titrE.tion lacks specificity because the solullilities of the alkali metal tetraphenylborates do not differ greatly (5). The stability of 1he calcium tetraphenylborate solution was evaluated by periodic standardization against standard potassium chloride solution. ’1 he apparent normality of the calcium tetraphenylborate solution decreased 1-, approximately 2.4% over a 10-day period. Frequent standardization is, therefore, indicated. The method descrilied here provides a
rapid and easily carried out procedure for the direct determination of univalent cations which form insoluble compounds with tetraphenylborate ion. It has the advantage over existing techniques for the determination of alkali metal ions of requiring relatively little equipment and time, but it suffers from the disadvantage of being nonselective with respect to the individual ions in this group. For the determination of a given univalent cation in a mixture, some prior chemical separation is required. Silver ions can be removed by the addition of chloride, ammonium ions by volatilization from alkaline media. Although multivalent cations do not interfere with respect to the electrode response of the alkali metal ions, there may be interferences because of the formation of other insoluble tetraphenylborates. Further work concerned with the application of cationic sensitive glass electrodes to analytical measurements is in progress.
LITERATURE CITED
(1) Bower, C. A., Soil Sei. SOC.d m . Proc., 23, 29 (1959). (2) Eisenman. G.. Rudin. D. D..‘ Casliv. ” , J. V., Science 126, 831 (1957). (3) Flaschka, H., Barnard, A. J., “Advances in Analytical Chemistry and Instrumentation,’’ Reilley, C. N., ed., Vol. I, pp. 10-29, Interscience, Sew York, 1960. (4) Geyer, R., Frank, H., 2. Anal. C‘hem. 179,99 (1961). (5) Katz, S. A., Rechnitz, G. A , , Ibzd., in press. (6) Mortland, hf. M., Quait. Bu/l., Mzchzgan Agrzcultirral Experzmental Stat i ~ 43, n 491 (1961). (7) Rechnitz, G. A,, Icatz, S.A., Dept. of Chemistrv. Universitv of Pennsvlvania. Philadelp”hia, unpubll’shed data,“1963. ’ (8) Taulli, T. A,, A 4 r . \ ~CHEM. . 32, 186 (1960). G. h R E C H ~ I T Z s. A. &TZ S.B. ZAMOCHNICK Department of Chemistry University of Pennsylvania Philadelphia 4, Pennsylvania ~
Investigation supported, in part, by S I H Grant GM-10086-01
Tit rimet ric A na Iy s is of 2,4,7-T rinitrofl uo re no ne Co m pIexe s SIR: Since Orchin and Koolfolk (8) reported that 2,4,;’-trinitrofluorenone entered into complex formation with polynuclear compounds, these complexes have proved to be exceedingly useful for the characterization and purification of this group of aromatics. The complexes are brightly colored, have high, sharp melting points, and are comparatirely easy to prepare. I n addition to melting point data, the trinitrofluorenone complexes may be iden1,ified by elemental analysis and by ultrs,violet and infrared spectra ( 7 >8). Laskowki and NcCrone (5, 6 ) proposed the use of trinitrofluorenone as a fusion reagent for the identification of other polynuclear arc niatics and investigated the use of this reagent for the ident’ificat’ion of simple benzene derivatil e3. Gordon and Huraux (4) dexribed spot tests for many aromat’ic comliounds utilizing trinitrofluorenone in which identification is made by color, fluorescence, and he3 t stability. Previous publicatisms (3, 9-1 1 ) have described titration ,f other nitroaroniatic compounds as mids using a quaternary ammonium h:.-droxide base. It was observed that 2,4,7-trinitrofluorenone as n-ell as the molecular complexes of trinitrofluorenone !rill similarly titrate as acids when dis.solri:d in pyridine. By using 0.01A- tetrabu tylammonium hydroxide as a titrant, the neutralization equivalent of the complexes may be ascertained even on 1Tery small samples. This value should serve as an important
aid in identification of over a hundred substances knoiyn to form complexes with trinitrofluorenone. EXPERIMENTAL
Procedure. T h e ao-oaratus a n d preparation of reagents j r e as previously described ( 1 , 2 ) . F~~~ 2 to 20 mn, of the trinitrofluorenone comp1e.r i, accurately weighed, dissolved in 50 nil. of pyridine,
Table I.
and titrated in an inert atmospliere n-ith 0.0lAY tetrabutylammonium hydroxide. The end point is determined from the potentiometric titration c u n x and corrected for the solvent blank. DISCUSSION
Figure 1 gives the titration curve for fluoranthene-trinitrofluorenone which typifies those obtained in analysis of the majority of these coniplexea. Table
Determination of 2.4.7-Trinitrofluorenone Comlslexes bv Titration with Tetrabutylarnrnonivrn H y d r o x i d e ’
Polynuclear component Perylene Fluoranthene Phenanthrene Chrysene Acensphtliene Pyrene Anthracene Benzo [alpyrene Fluorene 3-Methylcholanthrene Benz [a]anthracene 9-llethylanthracene Dibenz [ a , h ]anthracene 7,12-Dimethylbenz !a] anthracene Saphthalene a-?;aphthol @-Naphthol a Uncorrected.
Keutralization equivalent kkperimental Melting point, ‘C.
