V O L U M E 23, NO. 12, D E C E M B E R 1 9 5 1
1875
DISCUSSION OF RESULTS
cedure, it wm found that froin 8 to 15% of the total phosphorua of the carbide remains in the sludge after water slaking. Table I1 also shows that thc calculated phosphine percentages in the derived acetylene are in close agreement with those obtained by the recognized British Standard Institution method. Very little variation exists in the phosphine in acetylene resulta as obtained by this colorimetric method and by the conventional titrimetric way (last column, Table 11).
The results given in Table I clearly indicate the high degree of reproducibility of this new procedure. Although no standard samples were available for lime, calcium hydroxide, and calcium carbide, the results obtained are considered true, as no residual phosphorus was found in the fusion of the silica filter and all possible interferences from other elements usually present in these compounds were investigated. For carbide, the two methods recommended give identical re sults, which in turn check closely with the accepted British Standard Institution method. Table 11, where results of analysis of several carbide samples with various phosphorus content are given, shows the good phopphorus balance existing between total phosphorus in carbide as obtained by the nitric acid-slaking method and the phosphorus content of both gas and sludge determined by the water-daking, hypochlorite-absorption procedure. While using this last pro-
LITERATURE CITED
Brabson, J. A., Karchmer, J. 'H., and Katz, M. S.,IND.ISNO. CHEM., -4N.4L. ED.,16, 553 (1 944). ( 2 ) Hague, #J. I,.,and Bright, H. A , . J . Ruearch Natl. BUT.Standcrrds, (1)
26, 405 (1941). (3) Kitson, R.E.,and M e l l o ~ ~&I. , G., IND.ENG.CHEM.,ANAL.ED., 1 6 , 3 7 9 (1944). KECEI\ED ,June 5, 1950.
Infrared Absorption Spectrum of 1,2,3,4=Tetramethylbenzene P. J. LAUNER AND D. A. M C C A U L A Y Research Department, Standard Oil Co. (Indiana), Whiting, Ind.
YFRARED frequencies characteristic of the nuinber and '-position of substituting groups on an aromatic ring have been reported (1, 2, 5 ) for mono- and for all possible di- and trisubstituted benzene configurations. Of the three tetrasubstituted rings, frequencies associated v ith the 1,2,3,5- and 1,2,4,5- configurations have also been reported ( 6 ) , but the frequency characteristic of 1,2,3,4- substitution has not been established. Orr and Thompson ( 3 ) have pointpd out that a strong band betnetln 800 and 810 cm.? xppcars in the spectra of certain polrnuclcar
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aromatic hydrocarbons containing 1,2,3,4- substituted rings; they suggest that this band may be characteristic of 1,2,3.4 substitution. I n order to determine the characteristic frequency for 1,2,3,4tetrasubstitution, the authors have obtained the infrared spect r u m of 1,2,3,4-tetramethylbenzenc (prehnitene), 5hown in Figure 1. The intense band a t 804 c m - 1 is due t o the out-ofplane vibrations of the two adjacent C-H bonds of the aiomatic ring It has the frequcwc*\ ohserwd (3) for the more coniplex
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COMPOUND 1,2,3,4-TETRAMETHkLBENZENE (PREHNI TEN€ I A 1 0 2 - M M CELL B 0 4 3 - M M CELL C 4O%(VOL) SOLUTION IN C S z , 1 0 2 - M M CELL
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STATE TEMP PRISM
25OC NaCl
RESEARCH DEPARTMENT STANDARD OIL COllh3iANAl wnii
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ANALYTICAL CHEMISTRY
1876 hydrocarbons in which the 1,2,3,&wbstituents are parts of other aromatic rings.
a reference lo. The wave-length scale was calibrated with known absorption maxima of liquid toluene and of atmospheric water vaDor and rarbon dioxide. Wave lengths are accurate to L
EXPERIMENTAL
Preparation of 1,2,3,4-Tetramethylbenzene. 1,2,3,4-Tetramethylbenzene was prepared from pentamethylbenzene (Eastman Kodak Co.) by the Jacobsen migration reaction, according to the method of Smith and Lux (4). The product was fractionated on a 30-plate column and a center fraction (boiling point 205" C.; ng 1.5200) was taken for study. Infrared Spectrum. -4Beckman IR2 spectrometer equipped with a Brown recorder wa8 used. .\ rock salt plate was used as
*tb.O2p.
LITERATURE CITED
(1) Barnes, R. B., Gore, R. C., Stafford, K. W., and Williams, V. Z., ANAL.CHEM.,20, 402 (1948). (2) Colthup, N. B., J . Optical SOC.Am., 40, 397 (1950). (3) Orr, S.F. D., and Thompson, H. FV., J . C h a . Soc., 1950, 218. (4) Smith, L. I., and Lux, A. R., J . 4 m . Chem. Soc., 51, 2994 (1929). (5) Thompson, H. W., J . Chem. Soc.. 1948, 328. RECEIVED February 26, 1951
Dithizone as an Indicator in Titrimetric Determination of Zinc with Ferrocyanide .I.
1'. \IEHLIG AND A . 1'. GUILL', Oregon S t u t r College, Corrallis, Ore.
IPHENYLTHIOCARBAZONE, commonly called dithizone, has been uesd, because of the pink complex it forms nith zinc, as a reagent for the colorimetric and spectrophotometric determination of zinc (9,3, IO), and because of its extwrt ive powers it is the basis for certain titrimetric methods (9). 'Ylie puipose of the present work was t o establish the conditions for the use of the dithizone as an indicator in the titrimetric d
