1873
V O L U M E 23, NO. 12, D E C E M B E R 1951 peroxide, antimonl pentachloride ( I ) , and tungsten and vanadium compounds (7). Lenher and Crawford (7) stated that fluorides bleach the color when present in any amount, while water may be present up t o 20% without causing a fading of the color. LITERATURE CITED
‘1)
(2) (3) (4) (5) 6)
Bellucci, I., and Grassi, L.. dtfi. uccad. Lincei, 22 I, 30 (1913) Das Gupta, J . Indian Cheni. Soc.. 6 , 855 (1929). Eichler, H., 2. anal Chtm., 96, 17 (1934). Ekkert, L., Pharm. Ze?LtraZhnZZe, 75, 49 (1934). Hall, J., and Smith. ,J., Proc. A m . Phil. Soc., 44, 196 (1905). Kolthoff, I. M., and Sandell, E. B., “Textbook of Quantitative Inorganic Analyeis ” p. 70-1, S e w York, Macmillan (“I).. 1943.
(7) Lenher, V,,and Crawford, JY. G.. d . Ana. Chem. SOC., 35, 138 (1913).
(8)Muller. H. J., Ibid., 33, 1506 (1911). (9) Sandell, E. B., “Colorimetric Determination of Traces of Jletals,” p. 423, New York, Interscience Publishers, 1944 (10) Schenk, M., Helv. Chem. Acta, 19, 625 (1936). ;11) Shemyakin, F. -M., and Newmolotova, A., J. Gen. Chem (U.S.S.R.), 5, 491 (1935). 112) Tosburgh, K. C., and Coopei, G. R.. .J. A m . Chem. Sue., 63, 4% (1941). (13) Yoe, J. H., and Armstrong, A. R., Science, 102, 207 (1945). ’14) Yoe. J. H., and Sarver, L. -4.,“Organic Analytical Reagents,” p. 146, New York, John \Tiley & Sons, 1941. RECEJVEDDecember 2R, 1950.
Spectrophotometric Determination of Phosphorus In Limestone, Lime, Calciir m Hydroxide, Calcium Carbide, a n d Acetylene E. L. K 4CICOT, Shawinigan Chemicals, Limited, Shawinigan Falls, Que., Canada
HOSPHORUS, one of the c,hief impurities in calcium carbide, Prnust be determined with an accuracy difficult to obtain by the uwal gravimetric or volumetric procedures, because its content iri the raw materials used and in the finished product must be very low to give acetylene gas a i t h less than 0.05% phosphine by volume. Therefore, as a possihle solution, development of a photometric method o f analysip n as considered, m-hich will give both celeritv and accuracy, even R hen applied directly on calcium cnrbide. The literature reveal* t \+( I 1):i-k colorimetric procedures for phosphorus: the molybdenum blue method, applied to steel analysis by Hague and Bright (@, whereby the phosphorus is converted to the phosphoniolytdate, which in turn is reduced to the blue complex; and the niolybdivanadophosphate method where this yellow complex is ohtained by the action of ammonium vauadate and ammonium molybdate on the phosphorus. Preliminary tests showed that the conditions required for producing the yellow complex from the compounds under ronsideration are less critical than those for the blue complex, and that the former is more stable. These results are in agreement uith the findings of Kitson and XIellon (3). Therefore, the molybdivanadophosphate method &-as coIisitlrivtl the most suitable and reseurch was based on the w r h done by Brabaon, Karchnier, and K r t z (I), who adapted thic method to the determination of phosptiorus in limestone. The procedure conmtc essentially in oxidizing the phosphorus fuming with perchloric. acid, \vhich also serves to dehydrate the silic-athat must he filtered nut t)efore the yellon- molbydivanadophosphate is developed The color intensity is then measured on the spectrophotometer and the corresponding amount of phosplioius is read directly o n :L standard curve obtained b r similarly tic,veloping and measuring the color from various rnncentratinne of a solution of knomn phosphorus content. Spectral transmittance curves done with a Coleman \Iode1 11 L-iiioersal spectrophotometer o n ferric perchlorate and molyhdivanadophosphate solutions sho\red that at a nave length of 430 nip the effect on transmittance n a q a minimum for iron and a nia\imum for phosphorus. Rr&on, Karchmer, and Kata (1) recommended a 425 nip Illue filter, using a Fisher electrophotometer. Full color developriieiit o f the > ellow phosphorus coniple\ tooh approximately 20 minuter, :rftrr N hich the color remained Gtahle for at least 18hour. iddition of nitric acid ant1 50 inl. o f sodium hypochlorite (1 to 2% available chlorine) prior t o fuming with perchloric acid had no effect on the final color. Peichloric acid addition could he increased or decreased by as much as 25% of the recommended amount mithout affecting the final reaults.
I spectrophotometer or a filter photometer i s required. REAGEVTS
Ammonium Vanadate Solution. Dissolve 2.35 grams of ammonium metavanadate in approximately 400 ml. of hot water: add 17 ml. of 607, perchloric acid, cool, and dilute to 1 liter. Ammonium Molybdate Solution. Dissolve 100 grams of molybdic acid (85@;\ in a mixture of 300 ml. of water and 80 nil. of ammonium hydroxide. When dissolved, filter and boil filtrate 20 minutes; cool and dilute to 1 liter. Standard Phosphorus Solution. Determine, gravimetrically or volumetrically, the phosphorus content of a sample of anhydrous diammonium phosphate and weigh out an amount equivalent to 0. lOOOgram of phosphorus( theoretical amount of pure diammonium phosphate = 0.4263 gram). Dissolve in water and dilute to 1 liter; 1 ml. of this solution will he equivalent to 0.1 mg. of phosphorus. Sodium Hypochlorite Solution. Pass chlorine gas into a cold solution of 15mc sodium hydroxide and dilute so that the final solution contains not less than 1% and not more than 2% available chlorine when titrated with 0.1 N sodium arsenite. Saturate the portion needed with sodium bicarbonate (in excess) immediately before use. Perchloric acid, SO%, specific gravity 1.54. Concentrated nitric acid, specific gravity 1.42. RECOMMENDED PROCEDURES
For Standard Curve. Transfer five aliquots of the standard phosphorus solution, containing 0.1 to 0.5 mg. of phosphorus to 400-ml. beakers. *idd 20 ml. of 607, perchloric acid, boil to perchloric fumes, and fume gently for 5 minutes. Cool to below 100” C., add 10 nil. of ammonium vanadate solution, and stir. Let cool to room temperature and then transfer to 100-ml. volumetric flasks. h d d 7.5 ml. of ammonium molybdate solution, swirling the contents of the flasks to prevent precipitation. Dilute to the mark n-ith distilled water, mix thoroughly, and let stand 25 iiiinuteq foi full color development. Measure per cent transmittance on the Coleman ?*lode111 spectrophotometer balanced at 430 mp nave length, uiing distilled water as reference. Plot per cent ti ansmittance againqt concentration on semilog paper Thiq is a htraight line. Run a hlanh on all reagentq oii wch r i ~ vlot of reagents and make the propel caorrection. For Limestone. Transfer 0.5 to 2 grams of stone, depending on the phosphorus content, to a -100-ml. beaker. (If much organic matter is present, ignite the sample for 30 minutes at 900’ C.) Diesolve in 20 nil. of water and 20 ml. of 60% perchloric acid Boil to perchloiic fuineq, rover with a watch glass, arid fume slowly for 5 minutes. Cool to helo\\ 100” C., add 10 nil. of animoniuni vanadate solution, stir, and cool to I ooni temperature. Filter through a Whatman 41 H paper into a 100-nil. volumetric flask, washing out the beaker ell Wash paper and residue three times with &nil. portions of water. Be c:ireful that the final filtrate does not evceed 90 nil. *4dd i . 5 nil. of ammonium molybdate solution to this filtrate, snirling the contents of the flask to prevent precipitation. Dilute to the mark vith distilled water, mix thoroughly, and let stand for 25 minutes for full color development. Measure per cent
A N A L Y T I C A L CHEMISTRY
1874
transmittance on the Coleman Model 11 spectrophotometer balanced a t 430 mp, using distilled SECTION-I SECTION-Il water as reference. Read milligrams of phosphorus direct from the standard curve. For Lime. Use the same procedure as for limestone, but dissolve the sample with 20 ml. of 1 to 1 nitric acid before fuming with perchloric, NIthereby facilitating the dehydration of the silica and improving the filtration. For Calcium Hydroxide. As the phosphorus content of calcium hydroxide obtained from the slaking of calcium carbide is usually very low, use a 5-gram sample. Calcine a t 900" C. for 30 minutes, then transfer to a 400-ml. beaker, slake with approximately 10 ml. of water, dissolve, and boil a few minutes with 20 ml. of 1 to 1nitric acid. Oxidize with 20 nil. of 60% perchloric acid and continue as directed for limestone. Fer Calcium Carbide. NITRIC ~ I SLAKING D METHODfor total phosphorus in carbide (section I of Figure 1). Figure 1. Apparatus for Determination of Phosphorus in Calcium Warning. The carbide used in this method Carbide and Acetylene must be no finer than 65 mesh, in order to prevent explosions due to the very violent reSection I. For calcium carbide by HNOa slaking m e t h o d action of the nit,ric acid with the extrafine cara ~ ~ ~ t ; ~ ; ~ a l c carbide i u m by water-slaking, hvpochlorite~ab~rption bide. .is very fine carbide is difficult to screen method because i t balls up during the process, it is C. 500 ml. flask w i t h ground-glass neck, standard taper 29/42 B . 50-ml. graduated filling t u b e equipped w i t h suction tube, B', having ground the absence of fines . very imporbnt to glass connection, standard taper 29/42 by swirling the flask containing the 2-gram saniple E . Ffitted-glass bubbler, 125-ml. capacit>. and noticing that no balling occurs. Experience H . Transparent safety shield has shown that the f65-mesh fraction is of the same composition as the whole unscreened sample. Transfer a 2-gram sample of 65-mesh (through 28-mesh on 65boil the sludge to dryness, and bake for approximately 2 minutes. niesh) carbide (if phosphorus is greater than 0.03%, use a I-gram Let cool a little, then add 20 ml. of water and 20 ml. of 60% persample) to a 500-ml. Erlenmeyer; flask, C, connected to the fillin chloric acid. Continue as for limestone, using a Whatman No. 42 tube, B , with its suction tube, B , Set the flask in a bath of col8 paper (instead of a No. 41 H ) for the filtration water, D, to prevent possible explosion due to local overheating WATERSLAKING, HYPOCHLOR~TE ABSORPTION METHODto deduring slaking, and plaee the transparent shield, H,in front of the termine phosphorus separately in acetylene and sludge (Sections I flask as a safety measure. Make sure that no water is present and I1 of Figure 1). Transfer 2 grams of 65-mesh carbide to the inside the apparatus. 500-ml. Erlenmeyer flask, C, fit B and B' tightly over it, and conWith stopcock of B closed, add 20 ml. of concentrated nitric acid nect side arm of suction tube to the fritted-glass bubbler, E, con(specific gravity 1.42), stopper, and connect it to a source of containing 25 ml. of sodium hypochlorite solution of 1 to 2% availstant pressure nitrogen, aa given by a mercury column seal, A . able chlorine content. Then connect the bubbler to the 300-ml. Introduce the acid very slowly into the flask by gently opening flask, F, containing a strong caustic solution (soy0), which is in the stopcock and set a t a rate of approximately 30 drops a minturn connected to the 0.5-inch test tube, G, holding the mercuric ute, When the slaking is complete, let the nitrogen sweep all the chloride indicator, which will be reduced to the mercurous state, gas and fumes out of the system by running it for 5 minutes causing a turbidity if any phosphine had escaped the hypochlorite through the filling tube, the flask, and the suction tube to the exabsorption. haust. With stopcock of B clozed, add 20 ml. of water, stopper, and Take the flask from the apparatus, place it on a hot plate to connect it to a source of constant pressure nitrogen as given by A . Introduce the water a t such a rate that the bubbles of the evolved acetylene can barely be counted when passing through the caustic solution in F . When the slaking is complete, let the nitrogen sweep all the residual acetylene through the system by running it Table I. Phosphorus Determinations for 5 minutes through B. Disconnect C and E and analyze the On same samplea of limejtone. lime, calcium hydroxide, and calcium carbide) sludge and hypochlorite solution containing the phosphine sepaPhosphorus, % rately for phosphorus. No. of Detns. Average Maximum Minimum &le Sludge -4nalgsis. Add 10 ml. of nitric acid to the sludge in the flask and set it on the hot plate to dissolve. Boil and bring to Limestone 0.069 0.063 6 0.067 NBS. l a dryness. Bake for approximately 2 minutes and let cool a lit0.0072 0.0075 7 0.0073 Bedford tle .~ Add 20 ml. of water and 20 ml. of oerchloric and continue as Lime 10 0 0110 0 0116 0 0103 From Bedford stone for limestone, using a Whatman No. 42 paper for filtering. Calcium hydroxide Hypochlorite Analysis. Wash the hypochlorite solution out From caloium osrbide 7 0 0022 0 0026 0 0018 of the bubbler into a 400-ml. beaker. Boil down to approxiCalcium carbide Nitric acid-alaking method 6 0 0160 0 0165 0 0154 mately 20 ml. or until free from acetylene. Add 20 ml. of 6070 Water-slakinr hypochlorite perchloric acid and continue as for limestone, using a Whatman method 3 0 0159 0 0163 0 0156 No. 42 paper for filtering. For Acetylene Gas (Section I1 of Figure 1). Bubble Table 11. Phosphorus Determinations on Samples of Calcium Carbide 10 liters of acetylene through Calculated % 75 ml. of sodium hypochloPhosphine in % Gas from % Phosphme Actual In ,% Gas rite (available chlorine not % Phosphorus by Waterless than '% and not more G~ yield Phosphorus Found by British Method Slaking, Hypochloriteat 150 c. Absorption Method Slaking In In TitriColorithan 2%) placed in a frittedSample 760 Mm. Dry* glass bubbler, E. Transfer to No. Cu.Ft./Lb. In sludge In gas Total Method gas carbideQ metric metric a 400-ml. beaker and boil until 1 4.75 0,0010 0,0065 0.0076 0,0076 0,017 0.018 0,018 0.018 free from acetylene. Cool to 2 4.78 0,0018 0 , 0 1 1 0 0.0128 0,0125 0.028 0.028 0.027 0.027 room temperature. Transfer 0.033 3 4.77 0.0014 0,0122 0,0136 0,0137 0,031 0.031 0.032 4 4.64 0.0018 0,0158 0,0176 0,0180 0.041 0.041 0,039 0.039 to a 500-ml. volumetric flask, 5 4.24 0 0027 0.0180 0.0207 0.0206 0.051 0.052 0.055 0.057 dilute to mark, and determine 6 4.51 0.0036 0,0320 0.0356 0,0356 0,085 0.084 0.080 0.077 phosphorus on a 25-mi. aliquot as described under Stands Aasuming 12% of phosphorus remains in sludge after water-slaking carbide. ard Curve.
gzz::tnfli
~
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 9 4 4 ) . ( 2 ) Hague, #J. I,.,and Bright, H. A , . J . Ruearch Natl. BUT.Standcrrds, (1)
26, 405 (1941). R.E.,and M e l l o ~ ~&I. , G., IND.ENG.CHEM.,ANAL.ED., 1 6 , 3 7 9 (1944).
(3) Kitson,
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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