to determine N-phenyl-] -naphthylamine in used oils. The method is successful even with highly discolored (dark brown) oils, since the color intensity is greatly reduced by dilution with chloroform. The lower limit of detection for dark oils is about 20 p.p.m. of naphthylamine.
Table IV. Determination of N-Phenyl1 -naphthylamine in Mineral Oils
Wbi1% 5.44
Naphthylamine, P.P.M. Theoretical Found 54.4
54.2
LITERATURE CITED
(1) Allan, Z. J., Muzik, F., Chem. liaty
47,380 (1953). 4. (2) J., Ann. chim. (Rome) 44, . . Bertetti, J.. , 4 . 313 (1954). ' (3) Butt, L. T., Stafford, Stafford, N., J . Appl. Chem. 6, 525 (1956). (4) Deal, A. J. A., A,, Trans. Inst. Rubber h d . 23, 148 (1947).
(5) Engelbertz, P., Babel, E., Zentr. Arhei1,med. u. Arbeitsschutz 3, 161 (1053). (6) English, F. L., ANAL.CHEM.19, 457 (1947).
(7) Feigl, F., Costa Neto, Cl., Silva, E., Ibid., 27. 1319 (1055). (8) Hanot; C., Bull.. soc. chim. Belges 66, 76 (1957). (9) Koide, T.. Kubota, T., Furuhnshi, M., Sato, T., J . SOC.Rubber Ind. Japan 22, 108 (1949). (10) Lamhert, J. L., Cntes, V. E., ANAL. CHEM.29,508 (1957). (11) Levine, W. S., Marshall, W. A., Ibid., 27, 1019 (1955). (12) Liebhafsky H. A., Bronk, L. B., Ibid., 20,588 (1948). (13) Vaskevich, L). N., Sergeeva, 1 Gigiena i Sanil. 21, No. 3, 41 (1956). (14) Zijp, J. W. H., Elec. tzau. chim. 'I 313 (1957).
RECEIVEDfor review March 17 1961. Acrepted June 8, 1961. Divi6on of Analytical Chemistrv, 130th Meeting, ACS, S t . Louis. Mo., hfnrch 1961.
An a Iysi s of Tu ngste n-Tant a Ium- Rhe nium AI Ioys JAMES F. REED Westinghouse Research laboratories, Pittsburgh 35, Pa.
b In the analysis of alloys of tungsten, tantalum, and rhenium, acid hydrolysis is used to separate tantalum and tungsten from rhenium. Tantalum and tungsten oxides are dissolved by fusion with potassium carbonate and extraction with water. Tantalum is separated as the insoluble magnesium tantalate and weighed as the oxide after extraction of the magnesium salts with acid. The tungsten is precipitated from the acidified filtrate with cinchonine. Rhenium is precipitated in either dilute acid or alkaline solution as tetraphenylarsonium perrhenate. Tungstates, nitrates, and cinchonine do not interfere, but tantalum does. Small amounts of rhenium are separated from large amounts of tantalum by hydrogen sulfide.
A
these laboratories the alloy tungsten-tantalum-rhenium as well as the binary allnys tungsten-tantalum, tungsten-rhenium, and tantalum-rhenium were studied. The analytical methods required are described here. Since the literature revealed no method for the separation of the ternary system, conditions were established lor the simultaneous precipitation of tungsten and tantalum from rhenium by the combined action of cinchonine and acid hydrolysis. For small amounts of rhenium in the presence of tantalum the Geilmann and Lange (1) sulfide precipitation was modified to eliminate the pressure vessel. By complexing tantalum with fluoride its hydrolysis and precipitation under the Geilmann conditions were eliminated. T
The determination of rhenium was completed with the tetraphenylarsonium chloride method of Willard and Smith (6) as modified by Smith and Long (4). The interference, reported by Willard and Smith (6),of small amounts of nitrate was not a problem. Cinchonine and hydrogen peroxide also do not interfere. This method was preferred, because of its fewer interferences, to the nitron method (2). The method of Powell, Schoeller, and Jahn (9) for the separation of tantalum from tungsten as magnesium tantalate was modified to eliminate the ammonium salts and the tannin and yielded satisfactory results. EXPERIMENTAL
Reagents. Cinchonine, 10 grams dissolved in 90 ml. of hydrochloric acid ( 6 N ) . Tctraphenylarsonium chloride, 1% in water. Tctraphenylarsonium pcrrhenate, saturated solution in water for washing
(4).
Procedure for Ternary Alloys. HIGH RHENIUM. A . Dissolve about 0.2 gram of sample in 20 ml. of 6 N hydro-
chloric acid plus 5 ml. of hydrogen peroxide (30%). Dilute t o 100 nil. and add 10 ml. of cinchonine solution and 5 ml. of nitric acid. Boil until the peroxide is decomposed and set aside overnight a t room tempcrature. Filter through No. 42 Whatman paper. Save ::i tiltrate which contains the rhenium. B . Ignite the paper containing tantalum and tungsten in a platinum crucible until the paper is burned away. Add 5 grams of anhydrous potassium carbonate and fuse until clear. Cool and dissolve the melt in 50 ml. of cold
water. Rinse the crurible, and add 10 ml. of magnesium rhloride solution (10%). Stir and hcat to about 90" C. Let cool for 30 minutes, and filter the magnesium tantalate precipitate on No. 40 Whatman paper. Wash with 1% potassium carbonate solution. C. Acidify the filtrate with hydrochloric acid and add a 10-nil. excess. Boil out the carbon dioxide and add 5 ml. of nitric acid and 10 ml. of cinchonine solution. Allow to remain overnight a t room temperature. Filter through No. 42 U'hatmun paper and ignite to WOs i.n an electric muffle a t 800" C. D. Treat the paper and precipitate of magnesium tantalate with hydrochloric acid ( 1 N ) . Neutralize with ammonia to reprecipitate the tantalum. Filter and ignite over a Meeker-type burner until the paper is gone. Add hydrochloric acid (RN) to the tantalum oxidc to extract the remaining magnesium salts. Depant the clear liquid and ignite the residue to TazOs. E . The rhenium is in the filtrate from the acid hydrolysis of tantalum and tungstcn. Partially neutralize with ammonia, but leave cnough free acid to keep the cinchonine dissolved. Heat and add a 50% excess of tetraphenylarsonium chloride. Allow to remain overnight a t room tempcrature. Filter through a weighed fritted-porcelain crucible. Wash the precipitate with saturated tetraphenylarsonium perrhenate solution. Dry a t 110" C. and wcigh as (CaH&AsRe04. LOW RHENIUMALLOTS. F . If the weight of the rhenium is less than 10 mg. and tantalum is present, the rhenium is best separated as the sulfide. Dissolve the sample with 2 ml. of hydrofluoric acid plus a few drops of nitric arid in a platinum crucible. Heat to drive out nitrogen oxides. Transfer to a borosilicate glass or Teflon beaker conVOL. 33, NO. 10, SEPTEMBER 1961
* 1337
Table 1.
Determination of Tungsten and Tantalum
Added 2.9 19.6 47.5 71.8 84.6 95.8 96.5 118.9 176.1 183.8 Added 21.2 56.7 82.8 100.3 102.8 122.0 150.2 179.0
W, Mg. Found 3.1 19.9 48.1 71.1 83.3 96.2 96.7 117.6 176.4 184.5 Tal Mg. Found 21.6 56.7 82.6 100.2 101.8 120.8 151.9 180.6
Error
+0.2 $0.3 +0.6 -0.7 -1.3 +0.4
+0.2 -1.3 f0.3 +0.7 Error $0.4 0 -0.2 -0.1 -1.0 -1.2 f1.7 +1.6
taining 100 ml. of water and 1 gram of tartaric acid to complex tungsten, if present. Saturate with hydrogen sulfide. Heat to boiling and saturate again with hydrogen sulfide. Allow to remain overnight a t room temperature. Filter through medium porosity paper and wash with water saturated with hydrogen sulfide. Saturate the filtrate with hydrogen sulfide and heat again. If more precipitate forms, filter through the same paper. Dissolve the sulfide by pouring a solution containing 50 ml. of ammonium hydroxide ( 7 N ) and 10 ml. of hydrogen peroxide (30%) through the paper. Heat to destroy most of the excess peroxide, and add tetraphenylarsonium chloride to the ammoniacal solution. Finish the determination as described in E. BINARY ALLOYS.Tungsten-tantalum. Analyze by procedures B, C, and D. Tungsten-rhenium, If rhenium is less than 5% and HF must be used to dissolve the sample, determine rhenium by F and tungsten b C. If rhenium is higher than 5% a n J H F is not necessary to dissolve the sample, precipitate tungsten as in A , but ignite and weigh this precipitate as in C. On a separate sample dissolve as in A . Determine rhenium directly as in E after neutralization with concentrated sodium hydroxide until the solution is approximately 1N in sodium hydroxide. Tantalum-rhenium. If rhenium is less than 5y0 determine by F . If rhenium is higher than 5y0determine by A and D.
tantalum as magnesium tantalate yielded quantitative results (Table I), Spectrographic examination of the separated tantalum and tungsten oxides showed each to contain less than 0.1% of the other oxide. Ammonium salts and tannin were unnecessary for this separation. For the rhenium-tungsten binary it appeared that rhenium could be separated directly as the perrhenate if fluoride is absent. The data of Table I1 substantiate this. The separation of rhenium when present in small amounts is discussed below. Perhaps most difficult was the separation of rhenium in the presence of tantalum, for with large amounts of rhenium, recoveries are slightly and significantly low for the sulfide separation, according to the data of Table 111. (See also the precision data of Table V.) With small amounts of rhenium recoveries are again low when the acid hydrolysis-cinchonine separation is used as is apparent from the rhenium data of Table IV. However, if the correction factor developed in Table V and explained below is applied, rhenium values by the sulfide separation are quantitative at all levels explored. This procedure is particularly recommended for low levels, and it should be pointed out that items 1 and 3 in the table were obtained on the ternary system; the remaining data are for the binary rhenium-tantalum. In addition, under the conditions specified in F the Geilmann (1) pressure vessel is unnecessary. Moreover, the final precipitation of rhenium as the perrhenate was made in the presence of ammonium hydroxide and hydrogen peroxide, thus
Table IV.
Tantalum A, Mg. Error Added Found 101.3 102.8 +1.5 53.6 53.6 0 154.2 154.2 0 90.9 92.3 +1.4 20.1 20.10 _. 151.4 154.1 +2.7 39.6 -0.1 39.7 +0.2 10.4 10.6 3.2 3.4 +0.2 191.1 193.3 +2.2
Three separations were essential to the analyses described here. These were the separation of tantalum from tungsten, rhenium from tungsten, and rhenium from tantalum or, tantalum and tungsten. In the binary system tantalumtungsten, Schoeller’s (5) separation of
1338
ANALYTICAL CHEMISTRY
Table IA IB I1 I11
IV A IV B IV c
Added 12.7 22.9 63.0 80.2 101.6
System W in W-Ta Ta in W-Ta Re in W-Re Re after H2S Ta in Ta-W-Re W in Ta-W-Re Re in Ta-W-Re
Re, Mg. Found 12.7 23.0 63.4 81.1
101.3
Error 0
+o. 1 +0.4 +0.9 -0.3
Table 111. Determination of Rhenium after Sulfide Separation
Added 1.8
2.0 10.0 13.1 52.6 100.3 101.6
Re, Mg. Found 1.9 1.9 10.1 12.8 51.6 99.4 100.7
Error +o. 1
-0.1 t0.1 -0.3 -1.0
-0.9 -0.9
demonstrating no interference from these when used as specified. In the ternary system, the data for which are in Table IV, the rhenium was determined after the separation of tungsten and tantalum by the acid hydrolysis-cinchonine precipitation. Results are quantitative except for small amounts of rhenium and tungsten. After the separation the rhenium was precipitated in the presence of about 1M ammonium nitrate and 1 gram of cinchonine. Neither interfered although Willard and Smith (6) report that nitrate, except in low concentration, should be avoided. For binary alloys approximate analyses are obtained by volatilization of the rhenium aa the oxide by the Woolf
Ternary Alloys
Tungsten B, Mg. Added Found Error 46.0 45.9 -0.1 87.1 87.0 -0.1 79.9 79.3 -0.6 21.6 20.7 -0.9 167.6 168.8 11.2 ~. ~ . _ 24.6 24.3 -0.3 38.5 +1.1 37.4 179.1 -1.8 180.9 196.0 194.6 -1.4 1.4 0 . 3 -1.1
Table V.
RESULTS AND DISCUSSION
Table II. Determination of Rhenium in Tungsten-Tantalum
Rhenium C, Mg. Added Found Error 55.0 54.8 -0.2 49.6 50.0 $0.4 26.0 24.7 -1.3 92.0 92.1 +O.l 10.4 10.3 -0.1 31.6 32.1 +0.5 121.1 120.5 -0.6 9.9 10.0 +0.1 1.9 1.4 -0.5 1.9 1 . 5 -0.4
Statistical Data for y = bx
Slope, b 1.oo
1.00 1.00 0.99 1.01 1.00 1.00
95% Confidence Interval Std. Dev., Mg. 0.994-1.005 0.76 0.995-1.011 1.03 0.994-1.012 0.46 0.986-0.994 0.24 1.005-1.016 0.74 0.989-1.003 0.98 0.990-1.005 0.55
(6) method. A brief investigation showed that for both such binary alloys each remaining oxide contained about 1%of rhenium. ACCURACY AND PRECISION
The data presented in Tables I through IV were analyzed statistically. bx where y With Ghe model y = a represents the milligrams found and x the milligrams taken and a and b are the intercept and slope, respectively, it was found in all cases that a t the 95% confidence level, a did not differ significantly from zero. Consequently, the model
+
of the slope and the standard deviation for a single determination (y) are presented in Table V. +4$ value of 1.OO for the slope represents quantitative recovery. If the value is 0.99, as it is for rhenium by sulfide separation and the value 1.00 is not included in the confidence interval, then recovery is sigmficantly low and for practical use may be corrected to quantitative recovery with this slope value of 0.99. With the exceptions noted above for small amounts of tungsten and rhenium by the acid hydrolysis separation, the data of Table V indicate that all other recoveries are quantitative over the range covered.
y = bx
waa adopted where the terms have the =me meaning as before. The values
ACKNOWLEDGMENT
The statistical analyses were per-
formed by Douglas H. Shaffer of these laboratories. LITERATURE CITED
(1) Geilmann, W., Lange, G., 2. anal. Chem. 126, 321 (1944). (2) Geilmann, W., Voigt, A,, 2. anorg. Chem. 193, 311 (1930). (3) Powell, A. R., Schoeller, W. R., Jahn, C., Analyst 60,509 (1935). (4) Smith, W., Long, S., J. A m . Chem. SOC.70, 354 (1948). (5) Willard, H. H., Smith, G. M., IND.. ENG.CHEM.,ANAL.ED. 11, 305 (1939).
(6) Woolf, A., “A Method for Analysis. of Some Binary Alloys,” kssoc. Elect, Ind. Ltd., Research Lab., Report A480, (October 1955).
RECEIVEDfor review March 3, 1961. Accepted June 8, 1961. Work supported by Bureau of Aeronautics, Department of the Navy. Division of Analytical Chemistry, 137th Meeting, ACS, Cleveland, Ohio, April 1960.
Extraction and Flame Spectrophotometric Determination of Nickel HOWARD C. ESHELMANl and JOHN A. DEAN Department of Chemistry, University o f Tennessee, Knoxville, Tenn.
b Nickel is isolated from most other elements by a single extraction from a mannitol-aqueous ammonia solution at pH 9.6 with a 1% solution of salicylaldoxime in 4-methyl pentan2-one. The organic phase is aspirated directly into the flame. When using a ketone aerosol, the sensitivity is 0.16 pg. of nickel per ml. per 0.1 mv. (or per 1% on T-scale) which is approximately one eleventh the amount of nickel necessary to provide the same emission intensity when using an aqueous aerosol. The working curve is rectilinear for concentrations of nickel which do not exceed 30 pg. per ml. The effects of the following experimental variables were studied: flows of oxygen and acetylene, the optimum ratio of flows both for aqueous and ketone aerosols, the emission intensity from different regions of the flame mantle, and the spectral and radiation interference from 2 7 metals and six acids which are commonly associated with nickel. The extraction method was applied to samples of a sheet brass and a nickel-chromium steel. It should be of interest to analysts in production and control laboratories who need a more rapid and reasonably reliable method of chemical analysis for nickel. Present address, University of Southwestern Louisiana, Lafayette, La.
A
of flame photometry to the determination of nickel in metallurgical products are not as widespread as the utility of the method warrants. The method should be of interest to analysts in production and control laboratories who need a more rapid and reasonably reliable method of chemical analysis for nickel. The dimethylglyoxime separation and gravimetric determination of nickel, although widely used, are time-consuming, particularly in comparison with the flame spectrophotometric method. The titration of nickel with cyanide is undesirable because of the toxicity of the cyanide reagent and the indistinctness of the end point. When nickel is determined by the electrolytic method, small amounts of nickel are usually left undeposited. For amounts of nickel in the concentration range from 0.5 to 10 p g . per ml., the dimethylglyoxime extraction method is often employed. However, the intensity of the color increases gradually for approximately 30 minutes and then starts to fade slowly. The fading is avoided in the back-extraction modification of the method, but an additional step is introduced. In the present investigation a flame spectrophotometric method for nickel has been developed. Nickel is isolated from most other elements by a single extraction with a 4-methyl pentan-2one solution of salicykldoxime, after PPLICATIONS
which the organic phase is aspirated directly into the flame. The flame spectrophotometric method ha,. the advantage of speed, yet retaius the accuracy of the commonly used methods for determining nickel. Although Burriel-Marti and his coworkers (1) have described a method in which nickel is precipitated with dimethylglyoxime and extracted with chloroform, the nickel was stripped from the organic phase and ultimately determined in an aqueous medium. The back-extraction lengthened the determination and sacrificed the enhancement which can be achieved when an organic solvent is aspirated. For aluminum alloys, Dean and Cain (4) extracted nickel, as diethyldithiocarbamate, into chloroform and aspirated the organic phase into the &me. The nickel diethyldithiocarbamate reaction is not a t all selective and the reagent is unstable; moreover, 4methyl pentan-2-one is a more ideal solvent as compared with chloroform, since the latter releases obnoxious hydrogen halides into the burnt flame gases. In nickel-plating baths, Fornwalt (6) determined the nickel directly after adding 40% v./v. of methanol to intensify the emission. In the literature one observes a distinct lack of information which pertains to the best excitation conditions for nickel and the interferences which might prevail. Undoubtedly this void in our knowledge has hindered the use VOL. 33, NO. 10, SEPTEMBER 1961
1339
