io-phenanthrohe) is to be used or 10 to 60 y of iron if 4,7-diphcn+l,l(iphenanthroline (bathophenanthroiineji?: to be used. n i s o i v e t.he sampie in 1 0 mi. of S.0.Y hydrochloric acid ir. h small beaker, transfer this solution to a 125-d. separatorj- funnel, and complete tile quantitative transfer with exactly 8 mi. of 8.05 hydrochloric acid. Add I drop of 1.OM potassium permanganate and mix quickly. .4dd 25 ml. of isopropyl ether and mix the phases try shaking .vigorously for 1 minuti.. -4iiow the phases to separate, then draw off the aqueous phase into a second 12% mi. separatory funnel. .4dd n irtlsii %-mi. portion of isopropyl ether to the water layw and agaiii shake thr. funnel and contents for 1 minute. . U o w the phases to separate and draw o f f and discard the lower aqueous phase. Strip the iron from the second ether fraction by Shaking vigorously for 1 minute with'25 ml. of distilled
water. Allow the phases to separate and transfer the lower aqueous phase to the first ether fraction. Shake the phases in the first separatory funnel vigorously for 1 minute. Allow the phases to separate, then proceed with the analysls of this solution following the method of Fortune and hfellon (1) with o-phenanthroline, or the method of Smith, McCurdy, and Diehl (9) with bathophenanthroline. The calibration curves for each of these methods were based on direct colorimetric analysis of standard iron solutions. and arc, therefore, independent of the iropropyl ether extraction. Recoveries of added iron froiii zirwiium oxychloride and various phosphate salts are listed i n the table. Slight modifications of the extraction conditions are indicated as Method A, B, C, or D. The extraction of small amounts of
iron(II1) form 8N hydrochloric acid solution with isopropyl ether permits the extension of the very reliable snc! sensitive phenanthroline reagents T O systems which contain large amcunte of zirconium, phosphates, and other substances that otherwise interfere. Thp procedure has been most useful for t.hc determination of iron in such systems. UTERATURE CITED
Fortune, W. B.. Mellon, 11. G . , I s u ENG.CHEM.,ANAL.LD. 10,60 (1Y:B). (2) Gasner, V. K., %. n m l . Ciienr. 153. 6 (1956). (3) Smith, G . F., McCurdy, \V. H., Jr., Diehl. H., A m l y s l 77, 418 (1952). (4) Swift, E. H., J . A7n. Clieni. SUC. 56. 2573 (1936). F. H. ~ H M A P ; D. F. KUEMMEL E. %I. SALLEE The Procter Q Gamble Co. Cincinnati, Ohio (1)
Tetrac ya noet hy lene as a Cot or-DeveIo ping Reagent for Aromatic Hydrocarbons SIR: Many polyaromatic hydrocarImns can he separated by paper chromatograph! . Sumerous compounds can he located by ultraviolet light, but not all are easily located by this means. A spray reagent which would make the compounds visible in daylight would constitute a simpler method of location. A study of the preparation and reactions of tetracyanoethylene (TCNE), including kactions with some hydrocarbons has been recently reported (1). The color reactions with a wide variety of hydrocarbons on filter paper have been' investigated. When a small amount of the test compound was deposited on filter paper and sprayed with a benzene solution of tetracyanoethylene, only the alkylbenzenes and polyaromatics produced a colored spot. Most of the colors fade upon heating. Some of the compounds teated and the colors produced are given in Table I. Tetracyanoethylene, which is a solid, ie best sprayed onto the paper from a saturated solution in benzene. The identification Wit is on the order of IO4 gram. Using l,%benzanthracene as an index, the amount of compound found to be necessary for visual observation was about 4.5 X 10- gram per square inch. The tetracyanoethylene does not leave a background color on the paper unless the spraying is extremely
1740
mumw
CHEMS ITRY
heavy. The tetracyanoethylene used in this work was prepared by the dibromomalononitrile-potassium bromide complex method (1). Unless purified by sublimation, tetracyanoethylene darkens upon standing for extended periods and should be recrystallized prior to use. Table I.
Tetracyonoethylene-Hydrocarbon Colon
Compound Color Acenaphthene Green Anthracene* Blue-green 1,2-Benzanthracene Blue 2,3-Benzo5uorenea Light blue 3,4-Benzpyrene Dull brown Chrysenea Light blue 1,%Dimethylnaphthalene Blue-green 2,3-Dimethylnaphthalene Blue 2,6Dimethylnaphthalene Blue Hexamethylbenzene Red-purple 2-Methylanthracenea Green 1-Methylnaphthaiene %Methylnaphthalene 1-Methylphenanthrene purple Phenanthrene Dark red Pyrene Red-brown a Color fades particularly rapidly.
E:
Tetracyanoethplene is a n extremely active dienophile (9) and, as such. undergoes the Diels-Alder reaction with great facility. Thus, at least for those
compounds which show a rapid fading of color, one may postulate that the color fomiation and disappearance represent the formation of a transitoQr-complex between tetracyanoethylene and the polyaromatic, with subsequent reaction (Diels-Alder) to yield a colorless adduct. ACKNOWLEDGMENT
The authors express their appreciation t o the Shell Oil Co. for permission to publish this work. UTERANRE CITED
(1) Cairns, T. L., Carboni, R. A., Coffman, D. D., Engelhardt, V. A., Heckert, R. E., Little, E. L., McGeer, E. G., McKueich, B. C., Middleton, W. J., Scribner, R. M., Theobald, C. W., Winberg, H. E., J . Am. Chem. Soc. 80,
2775 (1958). ( 2 ) Middleton, W. J., Heckert, R. E., Little, E. L., Krespan, C. G., Zbid., 80, 2783 (1958).
PAULV. PEURIFOY STEPHEN C. SLATMAKER MAXWELL NAGER
Houston Research Laboratory SheH Oil do. P. 0.Box 2527 Houston I, Tex.
