pressure head of about 10 p.s.i.g. is maintained across the control vaive. .in using compressed mixtures of helium ;tnd nitrogen it seemed possible that one might obtain a diffusional separation of kelium and nitrogen through the control valve that would continually alter the composition of the compressed mixture. i n numerous repeat analylyses of gas discharged from the cylinder, there was 20 evidence that any such effect occurred to a significant extent. {We used a Perkin-Elmer Model 154 Y:tpor Fractometer. In piace of the kmal adsorption column we substituted :L line and bypsss containing a cold wap and sample tube similar to those described by Nelsen and Eggertsen. We obtain similar results both with and without the bypass, if the flow rate through the sample tube does not exceed about 25 ml. per minute. The principal advantage of the bypass is the smaller time required for a measurement. Total flow rate is monitored with a Brooks Flowmizer (Brooks Rotameter Co., Hatfield, Pa.) inserted immediately after the regulator, while flow through the sample tube is monitored through a similar flowmeter provided with the fractometer. The gas sample cell on the chromatograph provides a simple and convenient means of calihating peak areas with known amounts of nitrogen. The volume of the sample re11 :vas accurately determined. Coni-
position of the gas mixtures was carefully nnalped wit.li the Vapor Fractomekr using a wiumn p:ickii~g of Molecular Sieve. The total flow is set t o ahout 50 ml. per minute and the flow through the sample to about 25 ml. per minute. With the system described, the total flow was constant sufficiently long to permit several desorption and several caiibration measurements to be made. These modifications, though requiring a calibration with each desorption; practically eliminate problems in the control, metering, and measurement of flow which were otherwise the greatest source of ewerimentai difficulty. EXPERIMENTAL RESULTS
Measurements have been made on four samples whose surface area was previously determined by the conventional volumetric method in a vacuum system. The calculations are similar to those given by Nelsen and Eggertsen, except that the volume of nitrogen adsorbed, Vu, is obtained simply by the ratio of the desorption peak area to the calibration peak area times the calibration volume, corrected to standard conditions. This simplification results from the use of constant flow rate for both the desorption and the calibration. The comparative surface areas are:
Surface Area,Sq. hl./Gram Continuous ('at.alyst
flow
\'oIunwi ric.
'opper chromite Alumina Alumina Chromium -411 samples were powders, outgasscd The wgreeinent between the two methods is good, in spite of sonie differenre in oiitgussing procediire. For the volumetric nirthoci, :he saiiiples were outgassed :it 'LOO" (;. for 20 minutes under w r u u n ~ ;i n tiw continuous method, a t 200" C. for 30 minutes in a continuous stream of nitrogen at essentially atmospheric pressure. Duplicate measurements on the same sample a t a given relative pressure gave desorption peaks which agreed within about +2%. The Harshaw Chemical Co. furnished the catalyst samples as well as the surface area data reported above, using the volumetric method.
a t 200" C. for 30 minutes.
LITERATURE CITED
(1)
Nelsen, F. M., Eggertaeii, F. T.,
ANAL. ('HEM. 30, 1587 (1958).
JAMES F. ROTH ROBERT.I. ISr,r,wocm Central Research Lalmratory General Aniline I% Filni ('orp. Easton, Pa.
Determination of iron in Phosphate and Zirconium Salts SIR: 1,N-Phenanthroline and the :nore sensitive 4,7-diphenyl-l, 10-phenanthroline are very selective reagents for the determination of traces of iron (1, 3). However, substances which themselves precipitate or which form precipitates or more stable complexes with iron in the pH range 2 to 11 ,nterfere with the formation oi the colored complexes. Zirconium salts and phosphates are examples of such subrtances. G m e r (2) has recently reported the aetermination of small amounts of iron in commercial phosphate salts and phosphate rock with no prior separation, 7,lsing 2,a'dipyridine. The sample solu:ion was heated on the steam bath for 3 hours after the addition of reagents to develop the color. No data are prewnted to show, nor is it chimed, that xhe color so developed is equivalent to shat of an equal concentration of iron .n t
3
a
-4.
Material ZrOClr 8HZO
0 5
CaHPO,
0 4
CaHPO4 NaH2P04H 2 0(ACS) Cad'*& (comm.) NasP& CaHPO4 Y~HPO (ACS) ~ \ !'JHi)zHPO,(ACS)
C.
0 3 0 1 0 0 0 1 d '2
1 I
4
5 1 0 0 0
?e Added, y Decns. covered 5 1000 50-85 4 101 2 !*1W s 95 6 3(rm 3 96 2 io-150 3 96 8 1&50 0 1 101 7 '50-.so 4 97 0 2 100 0 50-100 3 101 6 20 3 100 1 .50 ' 3 99 2 '20-50
u/o
Method
I O
'1) (1)
0 6 0 8 1) I,
12
2 0 0 0
5 0
5 6 1 9
(il 'I) (1) (1) (1)
(1) (3) (3)
(3)
One ether extraction, one waLer wash of extract
3. i)ne ether extraction, two wawr washes of extract. C Two ether extractions, two w x k r washes of first extract, one wash of secondextract 3 'Two ether extractlom, one water wash of each extract (rerommended procedure) _ I _ -
___ __ VOL. 31, NO. 10, OCTOBER 1959
1739
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-Hydro-
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
carbon 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.
The authors express their appreciation t o the Shell Oil Co. for permission to publish this work.
Tetracyanoethplene is a n extremely active dienophile (9) and, as such. undergoes the Diels-Alder reaction with great facility. Thus, at least for those
Houston Research Laboratory SheH Oil do. P. 0.Box 2527 Houston I, Tex.
E:
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
