ACKNOWLEDGMENT given a value of 100. The formula given with the pattern normally is not The supplier of ferrocenes, Harold the. complete formula for the comRosenberg of the Materials Laboratory, pound but only for the substituted is thanked for his assistance. Neil hlcgroup or groups. I n general, unless Devitt’s contribution of infrared spectra noted otherwise a ith the pattern, the is gratefully acknowledged. compounds shown are of two types: monosubstituted, (C5HdR1)Fe(CsH6), and disubstituted, (C5H4R1)Fe(C5H4R2). LITERATURE CITED I t is this R notation that accompanies the powder pattern in Table 11, except (1) Bentley, F. F., Ihnton, M., Rausch, for ferrocene itself and bisferrocenylM., Srp, S . ,unpublished results. mercury for which complete formulas ( 2 ) Dunitz, J. D., Orgel, L. E., Nature 171, are shown. 121-2 (1953).
(3) Eiland, P. F., Pepinsky, Ray, J . Am. Chem. SOC.74, 4971 (1952). (4) Kealy, T. J., Pauson, P. L., A-ature 168, 1039-40 (1951). (5) Rausch, M., Vogel, M., Rosenberg, H.. J . Chem. Educ. 34. 268 (19.57). (6) Rausch, >I., Vogd; M.,’ Rosenberg, H., J . Org. Chem. 22, 900 (1957). (7) Rausch, M., Vogel, M., Rosenberg, H.. Zbid., 22. 903 (1957). ( 8 ) Rausch, &I., Vogel, M,,Rosenberg, H., Zbzd., 22, 1016 (1957). (9) Wilkinson, Geoffrey, Rosenblum, hl., Whiting, 31. C., Woodward, R. B., J. Am. Chem. SOC.74, 2125-6 (1952).
RECEIVED for review September 18, 1958. Accepted April 9, 1959.
Simultaneous Spectrophotometric Determination of Niobium and Tungsten Application to Complex Alloy and Stainless Steels BRUCE McDUFFIE,’ WILLIAM R. BANDI, and LABEN M. MELNICK
Applied Research Laboratory, United States Steel Corp., Monroeville, Pa. ,A thiocyanate method has been developed for the simultaneous spectrophotometric determination o f niobium and tungsten. After preliminary reduction o f tungsten(V1) t o tungsten(V) b y stannous chloride in hydrochloric acid solution, the total absorbance o f the niobium(\/) and tungsten(V) thiocyanates i s measured a t 400 mp in a 0.30M thiocyanate, 20 volume yo acetone medium. Oxalate is added to bleach the niobium color, and the absorbance due t o tungsten alone i s then measured. The difference in absorbances gives the niobium concentration. The method i s applicable in the presence o f tantalum, titanium, and molybdenum, elements which may b e found with niobium and tungsten in the mixed oxide precipitate from the acid-hydrolysis treatment o f steel and alloy samples. The method has been tested with various National Bureau o f Standards stainless steels and cobalt-base alloys.
T
increased dclmands for complex alloy and stainless steels for supersonic aircraft and missiles h a r e necessitated improved methods for the analysis of niobium and tantalum in steels that may also contain tungsten, molybdenum, and titanium. I n most chemical methods for determining niobium and tantalum in steel; HE
I Present address, Department of Chemistry, Hsrpur College, Endicott, N. Y.
the sample solution is acid-hydrolyzed, giving a complex mixed-oxide precipitate (19). Siobium and tantalum will precipitate quantitatively with this method, tungsten will precipitate quantitatively if cinchonine is added (10, 20))and titanium and molybdenum may precipitate partially, depending on the composition and metallurgical history of the sample. Existing spectrophotometric methods for the determination of niobium, tantalum, and tungsten in such mixtures include reactions of niobium with hydrogen peroxide (9, 18, 21), with thiocyanate (3, 4, 7 , 15-17), and with 8-quinolinol (13); reactions of niobium and tungsten with hydroquinone ( 2 , 1 1 ) ; and reactions of tantalum with pyrogallol ( 2 , 6 , 11. 16). All, however, are subject to interference by molybdenum, tungsten, and or titanium. For example. in the tentative ASTM method (2, 11) for determining niobium and tantalum in stainless steels, the tantalum-pyrogallol method has a very large titanium correction factor and significant niobium, tungsten, and molybdenum correction factors. Also, the niobium hydroquinone method has a large titanium correction factor, and the tungsten interference must be evaluated by differential spectrophotometry. Marzys (16, 16) has developed a procedure for the photometric determination of niobium and tantalum in various types of ores containing titanium. This procedure combines the thiocyanate-acetone method of Freund and
’
Levitt ( 7 ) for the determination of niobium with a modification of Dinnin’s ( 6 ) pyrogallol-hydrochloric acid method for tantalum, to enable the carrying out of both determinations on different portions of the same sample solution, n i t h very little interference from titanium. I n testing RIarzys’ procedure for niobium, i t v a s discovered t h a t the tungsten interference was not reproducible or stable. Freund, Wright, and Brookshier ( 8 ) and Crouthamel and Johnson (5) studied the reduction of tungsten(P1) to tungsten(V) and the development of the tungsten(V)-thiocyanate color. Apparently the concentrations of stannous chloride and hydrochloric acid used by Marzys caused a slow and somewhat erratic reduction of tungsten(T’1) to tungsten(1‘), with a consequently unpredictable d u e for the tungsten-thiocyanate abrorbance. It may have been possible to adjust Marzys’ conditions to make the tungsten interference more reproducible, but n-ould have required that the concentration of tungsten be determined on a separate portion of the sample solution. An alternative was to reduce tungsten(1-1) quantitatirely to tungsten(V) so that it would give its full thiocyanate color with niobium. Then, in view of the strong tendency of oxalate ion to complex niobium (1, 4, 14, 16), i t seemed that the addition of oxalate to the mixture might bleach the niobiumthiocyanate color without appreciably VOL. 31, N O . 8. AUGUST 1959
1311
affecting the tungsten-thiocyanate color. Therefore, conditions for the reduction and color development of tungsten and for the color development and bleaching of niobium mere studied to develop a procedure for the simultaneous determination of both eleiiients in the presence of tantalum, titanium, and molybdenum. EXPERIMENTAL
Apparatus. A Beckman hIodei B or DU spectrophotometer with 1-cm. cells was used for all absorbance measurements. Reagents. Stannous Chloride-Hydrochloric Acid Solution, 50 grams of stannous chloride dihydrate in 500 ml. of 12M hydrochloric acid; solution is 0.44-v in stannous chloride. Thiocyanate-Acetone Solution, 36.5 grams of potassium thiocyanate in 100 ml. of distilled water plus 250 ml. of acetone, diluted to 500 ml. m-ith distilled water; solution is 0.75Jf in thioc> anate and 50 volume yo in acetone. Reagent grade chemicals \vere used throughout, except for the following: Niobium Pentoxide. Assuming ignition of niobium metal granules, Fisher Scientific Co., purified grade, to the pentoxide, the weight of oxide o btained corresponded to a metal of 97 t o 98% purity. The tantalum content \\as less than 170, based on the tantalum-pyrogallol method (16). Tantalum Pentoxide. Assuming ignition of tantalum foil, Fisher Scientific Co., to the pentoxide, the weight of oxide obtained corresponded to a metal of 100% purity. The niobium content was less than 0.37,, based on the niobium-thiocyanate method of this paper. Standard Solutions. T h e general procedure used in preparing t h e standard solutions was t h a t of Marzys (15, 16). Weighed amounts of niobium pentoxide, tantalum pentoxide, titanium dioxide, molybdenum trioxide, or sodium tungstate were fused in 96% silica glass crucibles with 12.5 grams of fused sodium bisulfate, leached with 125 ml. of boiling 15% tartaric acid. and diluted with witer to 250 ml. in volumetric flasks. The metal concentrations used were in the range of 0.08 to 0.5 mg. per ml. Blank solutions of bisulfate, fused and leached with tartaric acid, were used to make dilutions of the original standard solutions. to control the concentrations of bisulfate and tartaric acid in the various experiments, and to test the behavior of the reagents themselves. PROCEDURE
Separation of Mixed Oxides from Steel and Alloy Samples. Dissolve a 0.5- t o 5-gram sample (containing less t h a n 65 mg. of niobium and 130 mg. of tungsten, but large enough t o give a t least 20 mg. of mixed oxides) in 50 ml. of hot 6J!f hydrochloric acid in a 600-ml. beaker, adding a few drops of 1631 nitric acid if necessary. (Use only unetched beakers.) Then add 5 ml. of 16Jf nitric acid and 6 ml. 13 12
ANALYTICAL CHEMISTRY
WAVE
LENGTH, m p
Figure 1. Spectral transmittance curves in thiocyanateacetone medium
of 70% perchloric acid. Carefully heat the sample nearly to dryness, and bake until completely dry. Cool, add 30 ml. of 12M hydrochloric acid, and dissolve salts. Evaporate to 20 ml. and dilute to 250 ml. n-ith distilled water. Add 60 nil. of 6% sulfurous acid and 10 ml. of a 10% solution of cinchonine in 6M hydrochloric acid, and boil for 10 minutes. Let stand a t least 1 hour. Filter through a Whatman No. 42 filter paper containing some pulp. Wash the precipitate with a solution containing 10 ml. of the cinchonine solution in 50 ml. of water. Transfer the paper to a quartz or 96% silica glass crucible, and ignite a t 700" to 800" C. The residue consists of the mixed oxides of niobium, tungsten, and tantalum, plus any titanium that coprecipitated and any molybdenum that coprecipitated and did not volatilize as the trioxide on ignition. Silica and traces of iron also will be present. Preparation of Stock Solution of Mixed Oxides. Fuse t h e mixed-oxide residue with 5.0 t o 12.5 rt 0.1 grams of fused sodium bisulfate (depending on n hether t h e final volume is t o be 100 or 250 ml.) until a clear melt is obtained, using as nearly as possible the same fusion conditions as in preparing standard solutions of niobium and tungsten for t h e calibration curves. Leach the melt with 50 or 125 ml. of boiling 15% tartaric acid solution for 15 minutes, or until a clear solution is obtained. Cool in ice water, transfer to a 100- or 250-ml. volumetric flask, and dilute to volume with distilled water. This stock solution can be analyzed for tantalum by the procedure of Marzys (16) as well as for niobium :md tungsten by the procedure belon.. Color Development and Measurement. Transfer a 2- to 5-ml. aliquot (containing about 0.05 t o 0.5 mg. of niobium and 0.05 to 1.0 mg. of tungsten) of t h e above stock solution t o a dry 50-ml. volumetric flask. Add
bisulfate-tartaric acid blank solution if necessary t o make a total volume of 5 ml. Add precisely 20.00 ml. of the stannous chloride-hydrochloric acid reagent, stopper loosely, and heat a t 50" C. for 10 minutes. Cool the flask under tap water, add precisely 20.00 ml. of the thiocyanate-acetone solution, mix thoroughly, and note the time. Cool to room temperature in a constanttemperature bath, add distilled m t e r to volume, and mix well. Again adjust to room temperature, and dilute to volume if necessary. Prepare a reagent blank simultaneously. About 15 minutes after the addition of the thiocyanate-acetone reagent, fill the first spectrophotometer cell with water. Fill a second cell with the reagent blank (the absorbance of the blank is reproducible), and a third cell, A, with the colored solution. Cover these cells. T o the remaining colored solution in the volumetric flask add 0.5 gram of finely powdered ammonium oxalate monohydrate. and shake until the solid dissolves. Fill the fourth cell. B, with this solution, and cover. Then, 35 minutes after addition of the thiocyanate-acetone reagent obtain the absorbance a t 400 mp of the blank against water, and of A and B against the blank or against water. The temperature of the solutions a t the time of reading should be rrithin +0.5" C. of the temperature x t which the calibration curve for niobium \vas prepared. The absorbance of the solution in cell A us. the blank gives the sum of niobium plus tungsten, Jyhile the absorbance of the solution in cell B us. the blank gives tungsten alone; thc difference gives niobium RESULTS A N D DlSCUSSlON
Spectral transmittance curves for niobium, tungsten, molybdenum, tantalum, and titanium under the condi-
tions of the regular procedure for color development are shown in Figure 1, for the wave length region 360 to 480 mp. (The absorbances for molybdenum, tantalum, and titanium are coniparatively small; therefore, t x o absorbance scales are used.) Absorbance maxima for t'he niobium(V)- and tungsten(V)thiocyanate complexes occur a t about 387 and 400 mp, respectively. The absorbances due to titanium and tantalum are v e p slight, and decrease with increasing wave length. For molybdenum the absorbance increases slightly up to 400 m p and then decreases wit'h increasing wave length. Molar absorbance indices for these elements a t 385 and 400 m p are given in Table 1. Because the molar absorbance index of tantalum is relatively lorn, it appears that a relatively large quantity of tsntaluni-10 mg.-could be added as a carrier to samples low in total mixed oxides, so that the precipitation of trace amounts of niobium and tungstm wmld he more nearly complete. Behavior of Tungsten. T h e use of 10 nil. each of tungsten solution and stannous chloride-hydrochlorir acid reagent, as specified by 1Iarzys (16, I 6 ) , gave a 6M concentration of hydrochloric acid prior to the addition of the thiocyanate-acetone reagent. and a final hj-drochloric acid concentration of 2.4111. I n viex of the xork of Freund et al. (3)and of C,routhamel and Johnson ( 6 ) it is not surprising t h a t under these conditions only about 10% of the tungsten(V)-thiocyanate color developed in 30 minutes. Changing the tungsten and reducing-agent solution volumes of 5 and 20 ml., respectively, gave a n initial 9.6.V hydrorhloric acid concentration, and a final one of 4.831. This resulted in much more rapid and complete color derelopmcnt--85 to 94% of maximum absorbance in 15 minutes, and 97 to 99% in 30 minutes. Heat'ing the solutions a t 50' C. for 5 to 10 minutes prior to t,he :&lition of the thiocyanate-acetonc rcagcnt further aided the reduction of tiingsten(TY) to tiiiigsten(V), so that full absorbance was rrbtained within 15 to 20 minutes after addition of the color-tlei-eloping reagent. Heating at' the boiling point e-iually satisfactory for dwcloping the tungsten color, but carc had to be taken to prevent the loss of h:,-drogen chloride by vaporization, bemuse this was found to affect thc absorlmnce due t'o niobium. The tungst,cri(5')-thiocj-anat,e complex, mice formed, is relativrly stable, being affectedonl). slightly b y changes in temperature or by changes in concentration of thiocyanat,e, acetone, or hydrochloric acid ( 6 ) . A final thiocyanate concentrabion of 0.30.1.1 was sufficient for adequate and reproducible color development,. Furthermore, the addition of solid ammonium oxalat,e to
io0
0601 3 00 MOLAR
4 00 C O N C E N T R A T I O N OF
5 00 HYDROCHLORIC ACID
I
Figure 2. Effect of hydrochloric acid concentration on niobium-thiocyanate absorbance 0.4 mg. Nb,'50 ml.
the color solutions did not cause a n y measurable change in absorbance. A plot of absorbance us. concentration for the tungstrn-thiocyanate color is linear up to a t least 1.1 mg. of tungsten per 50 ml. a t 400 mp, Behavior of Niobium. Niobium forms a much less stable complex with thiocyanate than does tungsten ( 4 ) . Table I1 shows that the absorbance may be increased by addition of a nonaqueous solvcnt, such as acetone, to the solution, or by a n increase in the thiocyanate concentration. I n the procedure as established, the thiocyanate and acetone concentrations are set a t 0.30M and 20 volume %, respectively, whereby the rolor due to niobium is sufficiently intense for accurate measurement and yet is almost completely bleached on shaking with 0.5 gram of ammonium oxalate monohydrate. For concentrations of niobium greater than about 0.5 mg. per 50 nil., a slight correction (less than 1%) for incomplete bleaching may be neceqsary.
Table 1. Molar Absorbance Indices in Thiocyanate-Acetone Medium
Ilolar Absorbance Index Element Niobium Tungsten Molybdenum Tantaluni Titanium
Table II.
885 mp
11,800 10,100 106 105 4.8
4 0 0 F 10,200
13,200 115 43
Effect of Thiocyanate and Acetone Concentrations on Development and Bleaching of Niobium Color"
Final Concn. Acetone, KSCN,:U vol. y* 0 30 10
*
I .9
Changing the hydrochloric acid concentration in the final solutions from 3.3M to 5.3M causes the absorbance of the niobium-thiocyanate solutions first to increase to a maximum then to decrease (Figure 2) in agreement with the data of Bacon and Nilner ( 3 ) . The increase may be due to the tendency of hydronium ions to decrease the activity of water, thus favoring the formation of thiocyanate complexes of niobium rather than aquo complexes ( 4 ) . The decrease in absorbance a t higher concentrations may be due to competing reactions of thiocyanate and chloride vvith niobium, which is known to form hydroxj--cbhloro complexes in high concentrations of hydrochloric acid (18). T o obtain a high absorbance and to have a n acid concentration consistent with that needed t o yield optimum tungsten readings, a concentration of 4.8-11 was chosen. Because small changes in the volumes of the stannous chloride-hydrochloric acid reagent and the thiocyanateacetone reagent affect the absorbance, these solutionq must be added hy pipet or buret. 12undy (17) and Freund and Levitt ( 7 ) hare sh0n.n that the absorbance of a niobium-thiocyanate solution decreases ryith increasing amounts of sulfate. Therefore, the amount of sodium bisulfate used for fusion of the mixed oxides must be controlled within 1 0 . 1 gram, and the duration and temperature of the fusion must be reproduced as nearly as possible, so t h a t the concentration of sulfate or bisulfate in the final solution (0.04-If) will be nearly the same in all experiments. The final concentration of tartaric acid in the solutions is held at 0.045111. The effect of heating niobium solutions after the addition of the stannous chloridehydrochloric acid reagent. but prior t o addition of the thiocyanateacetone reagent, was investigated hecause heating was necessary for cornplete reduction of tungsten(V1) to tungsten(V). Heating below 100" C. had no cffect, because niobium(V) is not reduced by stannous chloride. However, boiling the solutions 5 or 10 minutes resulted in decreased absorbances, presumably because of a gross
Absorbance a t 405 P ~ I H ~
Bleaching of Color with Oxalate 0 46 Complete 0 30 20 0 90 Complete 0 30 30 1 18 Pract. complete 0 60 10 1 52 Incomplete 0 60 20 1 70 Incomplete Regular procedure for color development, except for variations noted above. 0.4 mg. Nb/50 ml.
VOL. 31, NO. 8, AUGUST 1959
1313
0940,
100,
Figure 3. Temperature thiocyanate color
of niobium-
dependence
0.4 mg. Nb150 ml.
loss of hydrogen chloride vapor. Any such loss by vaporization would change the hydrochloric acid concentration of the final solution, with a consequent change in absorbance (Figure 2 ) . For this reason stoppered flasks, and a temperature of 50" C., well below the boiling point, are recommended. Figure 3 shows that under the conditions of the final procedure the absorhance of niobium-thiocyanate solutions decreases markedly with increasing temperature in the region 20" to 35" C.
Table 111.
development 0.4 mg. Nbi50 ml.
At 25" C. the temperature coefficient is -1.5% per degree rise. Hence all solutions must be brought to constant temperature ( *0.5" C.) before absorbance measurements are made, or an appropriate temperature correction factor must be applied.
Analysis of Mixtures of Niobium and Tungsten Standard Solutions
Present, Mg. Kb IT 0 079 0 135 0.079 0 270 0.540 0.079 0.135 0.236 0.540 0,236 0.394 0.135 0,270 0.394 0 394 0 540
Found, Mg, h'b 0 077 0 081 0 .os2 0.234 0,241 0.393 0,398 0 405
Relative Error, 70 Nb IT -2 5 1.5 2 5 -n 4
w
0 137
0. 2fiQ -._
0.537 0.132 0,539 0.141 0.274 0 550
iiv.
3,8 -0.8 2.1 -0.3 1.0 2 8 2.0
-0.6 -2.2 -0.2 4.4 1.5 1.9 1 6
Determination of Niobium and Tungsten in National Bureau of Standards Samples
Table IV.
Sample5 Composite of KBS
Partial Composition,b 70 Ta Ti Mo Nb W
121b, 123b, 160a 0.08
KBS 123a
002
NBS 123b
0 20
Composite of S B S 121b, 168
Determined,
70
Nb
0 . 6 3 0 . 3 0 0.072 0 . 2 9 0 28 0 0 0 2 0 1 2 0 7 5 0 1 1 0 7 7 074 0 006 0 17 0 75 0 18 0 77 0 76
0.17
W
Relative
Error, 70 Nb IT'
0,072 - 3 . 3 0 072 0 1 3 1 3 011 0 17 2 7 0 17
0.0 9 1 -5 6
0 32
0 29
1 32 0 98 1 32
0 93 0 95
1 31 1 33
-4 1
0.0
0026
027
130 105
150
3 3
315
450
4
295395
156 1 53 447 4 47 4 0 4 4 04 4 03 4 04
1 9
3 9
109 1 04 321 3 27 2 9 4 2 97 2 97 3 00
Cornonsite of XBS 121b, 167
NBS 167
0 08
XBS 168
095
006
Bv.
2 9
-07
0 7
2 3
2 4
3 0
a 121b is titanium-stabilized stainless steel; 123a and 123b are niobium-stabilized stainless steels; 160a is molybdenum-stabilized stainless steel; 167 and 168 are cobnltbase alloys high in chromium and nickel and low in iron. * Only provisional certificates for 123a, 123b, 160a, 167, and 168.
13 14
ANALYTICAL CHEMISTRY
The rate of development of the niobium color under the conditions of the final procedure is shown in Figure 4; the absorbance is essent'ially constant 35 minutes after addition of the bhiocyanate-acetone reagent. Failure to cover the spectrophotometer cells caused a decrease in the niobium-thiocyanate absorbance, presumably due to the loss of acet'one by evaporation. As shown in Figure 1, the niobiumthiocyanat'e absorption curve has a maxinium a t 387 nip> but in the final procedure, readings were made a t 400 nip, the wave length of niasinium absorption for tungsten. to ininimize interference from tantalum and from the reagents. At' this wave length the niobium absorbance is about 87% of its value a t 387 mb. The calibration curve for niobium a t 400 mp is linear up to at least 1.0 mg. of niobium per 50 ml., in cont'rast with the findings of Mundy ( 1 7 ) for slightly different' conditions. Some preliminary experiments, calibration curves, and analyses ivere done a t 405 instead of 400 mp (Table
11). Reagent-Blank Characteristics. The reagent blank has a small but appreciable absorbance t h a t increases linearly with time and decreases with increasing wave length. For example, at 405 mp the blank absorbance in one experiment was 0.008, 0.014, and 0.026 after 15, 35, and 75 minutes, respectively. A t 385 mp the corresponding absorbances m-ere about three times as high. The blank absorbance a t 35 minutes, the time required for coiiiplete development of the niobium-thiocyanate color) is reproducible, so that' in routine m-ork the colored solutions can be read us. distilled ivater and a correction subtracted for the reagent blank. Evaluation of Method. The reeult,s obtained from eight different mixtures of the niobium and tungsten standard solutions using t'he regular color development procedure
arc shown in Table 111. T h e averagv relative errors are 2.0 a n d 1.6% for niobium and tungsten, respectively. I n analyzing synthetic mixt’ures cont’aining niobium and tungsten together Iritli molybdenum, titanium, and tantalum, no interaction of the latt,er three with niobium or tungsten was observed. hIolybdenum appears to he reducwl t.0 the trivalent state in the procedure. and the molybdenum(II1). titanium. and tantalum do not affect t h r formation of the niobium- and tungstrn(V)-thiocyanate complexes. B>. contrast. a molybdenum-tungsten interaction was noted a t lower concentrations of the strannous chloride-hydrochloric acid reagent, the characteristic oranpc of tho niolybdenuni(V)-thiocyanate lwing obtained not with molybdenum alone. hut when tungsten was present with molybdenum : this is similar t,o the well known influence, of copper and iron on tlw formation of the molybdenuni(V)thiocaynnate complex ( 5 ) and to the act,ion of titanium and iron in proniotiiiy the formation of thiocyanate complexes of tunpstrn and vanadium ( 1 7 ) . The niobium and tungsten results for Sational Bureau of Standards (YES) saniples of stainless steel, cobaltbasc alloy. and soiii~composite Ptandartls a r c prescntect in Table IT‘. For nitrbium. over the range 0.30 to 3.15y0,and for tungst’en. over the range of 0.072 t ( J 4.50% the average relative errors arc’ 2.4 and XO%, respectivelj-. H o w i - e r . the S B $ valurs for samples 1233. 123b. 160a. 167. a n d 168 are only provisional. Furt1ic.r. thc methods used in oht’aining the SBS values are tediouh and tiine-c.onsuniing. and are accurate only when used 1)y an experienced analyst,
This method is fast enough to be useful in routine analyses, and is considerably more rapid than the tentative A S T l I hydroquinone method (2). Apparently a single hydrolytic precipitation gives sufficient separation of the mixed oxides from the large amounts of iron, chromium, nickel, and cobalt present in the various NBS samples analyzed. Although these samples contained up t o 4% molybdenum, 0.3% titanium, 1% tantalum, and varying amounts of other elements, no corrections for interfering elements were necessary. The absorptivities of tantalum. titanium, and molybdenum are 90 small that the amounts in the samples would not cause appreciable error. I n addition, not all the titanium and molybdenum would be collected in the niiyed-oxide precipitate, and most of the molybdenum so collected would be volatilized on ignition of the precipitate, especially if the ignition proceeds for a long period. Thus it is probable that the method could be applied to samples much higher in titanium and molybdenum without the necessity for any corrections. ACKNOWLEDGMENT
The assistance of Ernest G. Buyok and Howard S. Karp of the United States Steel Corp. Applied Research Laboratory in developing and testing the proposed method is gratefully acknowledged. LITERATURE CITED
(1) Alimarin, I. P., Podvalnaja, R. L.. Zhzrr. ilnal. K h i m 1, 30 (1946).
( 2 ) d m . Soc. T:sting
hhterials, Philadelphia, Pa., .A.S.T.?rl. Methods for Chemical Analysis of ?*Zetals,” pp.
150-7, 1956. (3) Bacon, A,, hIilner, G. W. C., Anal. Chim. Acta 15, 129-40 (1956). (4) Crouthamel, C. E., Hjelte, B. E., Johnson, C. E., A x . 4 ~CHEM. . 27, 507-13 (1955). ( 5 ) Crouthamel, C. E., Johnson, C. E., Zbid., 26, 1284-91 (1954). (6) Dinnin, J. I., Zbid., 25, 1803-7 (1953). 17) Freund, Harry, Levitt, A. E., Ibid., 23, 1813-16 (1951). (8) Freund, Harry, Wright, L. M., Brookshier, R. K., Zbzd., 23, 781-4 (1951).
Hillebrand, W.F., Lundell, G. E. F., Bright, H. .4., Hoffman, J. I., “Applied Inorganic Analysis,” 2nd ed., pp. 60910 W’iley,New Pork, 1953.
(9)
(10) Zbid., pp. 689-93. (11) Ikenberry, Luther, Martin, J. L., Boyer, R. J., ANAL.CHEX. 25, 1340-4 (1953). (12) Kanzelmeyer, J. H., Ryan, Jack, Freund, Harry, J . A m . Chem. SOC. 78, 3020-3 (1956). (13) Kassner, J. L., Garcia-Porrata, -4sdrubal, Grove, E. L., Axax,. CHEW27, 492-4 (1955). (14) Lauw-Zecha, A. B. H., Lord, S. S., Jr., Hume, D. N., Zbid., 24, 1169-73 (1952). (15) Marzys, -4. E. O., Analyst 79, 327-38 (1954). (16) Ibid.,80, 194-203 (1955). (17) Mundy, R. J., ANAL. CHEN. 27, 1408-12 (1955). (18). Palilla, F. C., Adler, Korman, Hiskey, C. F., Zbzd., 25, 926-31 (1953). (19) Pigott, E. C., “Ferrous Analysis,” PD. 315-16, Wiley, Sew York, 1953. (20i Ib?d., pp. 805-10. (21) Telep, George, Boltz, TI. F., ANAL. CHEK 24, 163-5 (1052).
RECEIVED for reviexy Sovember 4, 1958. Accepted February 4, 1959. Presented in part at Ninth Annual Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Alarch 1958.
Infrared Determination of Nitrocellulose in Mixtures of Cellulose Resins HELEN M. ROSENBERGER and CLARENCE J. SHOEMAKER Chemical Research and Engineering Department, A.
b Nitrocellulose can b e determined quantitatively in the presence of other cellulose resins b y utilizing the characteristic 1 1.92-micron absorption band. The method described is r a p i d and simple. The results obtained on synthetic mixtures of known composition indicate a maximum deviation of I t l % and a mean deviation of +0.4% as determined from four separate samplings of each mixture.
P
B. Dick Co., 5700 West Touhy Ave.,
plasticized solutions of nitrocellulose are widely used in protective and decorative coatings. In the graphic arts field they are the basis for lacquers and paper coatings. In these formulations the major resin component, nitrocellulose, is frequently used in conjunction with other compatible resins such as cellulose acetatc. cellulose acetate propionate, and cellulose acetate butyrate. Modified IG~IIESTLD,
Chicago 48, 111,
maleic rosinq, ~~licnolformaldeliyde resins, and phthalic alkyd resins are also incorporated into such coatings. These coatings may also contain traces of aldehydes, alcohols, and plasticizers. The nitrocellulose employed in these mixtures is usually of the R S (estersoluble) type containing 12.0% nitrate nitrogen. Frequent analysis of such coating materials required a rapid method for VOL. 31, NO. 8, AUGUST 1959
1315
