1902
ANALYTICAL CHEMISTRY
Table 111. Reproducibility Series, Grease Method Element
Wt.
%
No. of Analyses
Coefficient of Variation
Max. Dev. of Element,
%
- 19 Li
0.20
10
9.2
Ca
0.60
10
4.1
Ka
0.30
10
3.3
Ba
0.40
10
5.0
AI
0.25
10
3.3
who are working in this direction may benefit by the work done in the authors’ laboratory.
4-13
+-- 844 .. 78 +- 4.0 5.0
ACKNOWLEDGMENT
The authors wish to express their gratitude to Eskil Gross and C. E. Marquart for the spectrographic analyses, and to the Richfield Oil Corp. for permission to report these results.
fl0.l
+- 45 .. 87
about 50 to 60 minutes for the analysis of a single sample. A considerable economy in processing and analyses can thus be obtained by this method. Table I11 shows a statistical evaluation obtained from the analyses of several synthetic greases of known composition. These so-called greases were prepared from chemically analyzed metal salts of organic acids and suitable solvents including lubricating oil. The coefficient of variations obtained show that acceptable results may be obtained by this method. Additional data will be required to completely evaluate the method on all types of greases; however, the procedure has given sufficient promise that it is being submitted to the industry so that others
LITERATURE CITED
(1) Barney, J. E.,11, and Kimball. W. -4..ANAL. CHEM.,24, 154850 (1952). (2) Calkins, L. E.,and White, M. >I., YuV. Petroleum News, 38, R519-30 (1946). (3) Gambrill, C. M., Gassmann, A. G., and O’Neill, W. R , . i ~ 4 ~ CHEW,23, 1365-9 (1951). (4) Hansen, J., Skiba, P., and Hodgkin, C. R., Ibid., 23, 1362-5 (1951). (5) Harvey, C. E.,“Spectrochemical Procedures,” Glendale, Calif., Applied Research Laboratories, 1950. (6) Key, C. W., and Hoggan, G. D., - 4 ~ 4CHEW, ~. 25, 1673-6 (1953). (7) Meeker, R. F., and Pomatti, R. C., Ibad., 25, 151-4 (1953). (8) Pagliassotti, J. P., and Porsche, F. W., Ibid., 23, 1820-3 (1951). RECEIVED for review M a y 26, 1954 Accepted September 13, 1964 Presented before the Division of Refining. American Petroleum Institute, Houston Tex , M a y 1954
Separation of Titanium Combined with Spectrophotometric Determination of Titanium in Steel JOSEPH R. SIMMLER, K A R L H. ROBERTS, and S A M U E L M. TUTHILL Department o f Chemical Control, Mallinckrodt Chemical Works, St. Louis 7, M o .
A new quantitative separation of titanium from titanium-bearing steels (0.05 to 1.0% titanium) has been utilized as the basis of the procedure described. The titanium is coprecipitated with added zirconium when the zirconium is precipitated as the arsenate from a strongly acid (1N) solution. This technique separates titanium from the usual elements in steel, and particularly from vanadium, molybdenum, and chromium. The titanium is then determined spectrophotometrically in the presence of zirconium as the peroxytitanium complex.
T
1TANIUP.I in steel is often determined by the colorimetric method based on the yellow color that develops when hydrogen peroxide is added to an acid solution containing titanium. This procedure is subject to serious interferences from elements which form colored ions in solution, such as iron, nickel, and chromium, or colored peroxy compounds, such as vanadium (8), molybdenum ( 9 ) , and columbium ( a ) ; and from ions which bleach the color of the peroxy-titanium compound, such as fluoride (i‘), phosphate (IO), and large amounts of alkali salts ( 4 ) . Some of these interferences may be overcome by the addition of the interfering species to the standard solution, but such a technique is not satisfactory in practical analysis, because it requires previous knowledge of the kind and amount of interfering elements. The usual separation procedures are discussed by Lundell, Bright, and Hoffman (3). Pribil and Schneider (6) showed that titanium may be quantitatively precipitated as the hydroxide in the presence of iron, mercury, copper, lead. bismuth, and nickel, provided the disodium salt of ethylenediaminetetraacetic acid is used as a complexing
agent. Pickering ( 5 ) recently adapted this techpique of separating titanium to the rapid determination of titanium in titaniferous ores. Feigl and Rajmann ( I ) , in developing a specific qualitative test for titanium, showed that titanium is coprecipitatcd with zirconium arsenate from a strongly acid solution, and they used this phenomenon as a means of separating small amounts of titanium from large amounts of iron, vanadium, and chromium. This suggested the possibility of quantitatively determining titanium in titanium-bearing steels by combining this separation with a spectrophotometric method for the final determination. Such a procedure would combine the advantages of a simpler means of separating titanium from steel components and an over-all shortening of the elapsed time for the analysis. The present paper describes the development of such a procedure. APPARATUS AND REAGENTS
Spectrophotometer. Beckman Epectrophotometer, Model DU; 1-cm. Corex cells. Titanium Standard Solution, about 1 mg. of titanium per ml. Add 0.85 gram of titanium dioxide to 5 grams of ammonium sulfate and 25 ml. of sulfuric acid in a 500-ml. Erlenmeyer flask and heat until solution is effected. Cool, dilute to approximately 400 ml., filter into a 500-ml. volumetric flask, and dilute to volume. Standardize the solution by precipitating the titanium in 25.00-ml. aliquots with dilute ammonium hydroxide and finally igniting and weighing as TiOn. Zirconium Solution, 1%. Dissolve 2.78 grams of zirconium sulfate in 100 ml. of 20 volume yo hydrochloric acid. Arsenic Acid Solution,. 20%. g r a m of arsenic .~ Dissolve 20.0 acid in 100 mi. of water. Wash Solution. Place 1.0 ml. of the 20% arsenic acid solution in a 100-ml. volumetric flask and dilute to volume with 10 volume % hydrochloric acid.
.
V O L U M E 2 6 , NO. 1 2 , D E ~ E M B E R1 9 5 4 Arsenic acid, 85% minimum. Ammonium hydroxide, 58% by weight. Hydrochloric acid, 37% by weight. Hydrofluoric acid, 48% by weight. Hydrogen peroxide, 30% by weight. Sulfuric acid, 96% by weight. PROCEDURE
Digest 1.00 i0.01 grams of steel turnings with 20 ml. of 1 to 1 hydrochloric acid on the steam bath until a crust forms. Add 10 ml. of hydrochloric acid and 30 ml. of water, heat nearly to boiling, and filter while still hot through a 9-em. Whatman No. 40 filter paper. Collect the filtrate in a 100-ml. volumetric flask. Wash the pa er and precipitate four times with 1%hydrochloric acid and a d f the washings to the filtrate. Char the paper and precipitate in a platinum crucible and finally ignite over a blast burner for 15 to 20 minutes. Cool, add a drop of sulfuric acid and 5.0 ml. of 48% hydrofluoric acid, and evaporate t o dryness on a hot plate. Add 1.0 gram of potassium bisulfate and fuse. rotating the melt so that as it cools it solidifies in a thin layer on the inside walls of the platinum crucible. To the cooled melt add 18 ml. of dilute sulfuric acid (1 to 10) and heat until solution is complete. Add this solution to the original filtrate and dilute to volume. Transfer a 10.0-ml. aliquot to a 15-ml. conical tipped centrifuge tube. Prepare a reagent blank hy placing 10 ml. of 1.V hydrochloric acid in a 15-ml. centrifuge tube and treat exactly like the aample. Add 1.0 ml. of the 1% zirconium solution, mix well, and add 1.0 ml. of the 20% arsenic acid solution. Stir the solution, let the precipitate settle for 3 minutes, and then centrifuge. Decant the supernatant liquid into another 18-ml. centrifuge tube which contains 1.0 ml. of the 1% zirconium solution. Stir. let the precipitate settle for 3 minutes, and centrifuge. Decant and discard the supernatant liquid. To each precipitate in the centrifuge tubes add 10 ml. of the wash solution, stir well with a stirring rod, centrifuge, and decant and discard the supernatant liquid. Dissolve the precipitate in one of the tubes by adding 2.5 ml. of sulfuric acid, rotating the tube so that the entire inside is wetted. Pour the solution into the other centrifuge tube. Wash the first centrifuge tube with 10 volume % sulfuric acid solution and collect the Tvashings in a 25-ml. glass-stoppered graduate. Dissolve the precipitate in the second centrifuge tube and transfer the solution and n-ashings to the 25-ml. graduate. Cool to room temperature and dilute to volume. To develop the titanium peroxide color. rinse a Corex cuvette with the test solution, fill the cuvette, and add 1 drop of 30% hydrogen peroxide. Mix the solution and measure the absorbance a t 410 mp us. a 10 volume % sulfuric acid solution. Determine the titanium content of the sample by reference to the standard titanium curve and correct for the reagent blank if necessary.
1903 P R E ~ E NOF C EMOLYBDESUM A N D VANADIUM. To determine the effectiveness of the separation from molybdenum and vanadium, 1.00 and 0.50 ml. of the standard titanium solution were placed in separate 15-ml. centrifuge tubes, followed by 10 mg. of molybdenum as ammonium molybdate. One milliliter of hydrochloric acid was added to each tube, and the solution was diluted to about 10 ml. A second set of tubes was prepared in the same manner, with the exception that 10 mg. of vanadium as ammonium vanadate was added instead of molybdenum. The titanium was then separated and determined according to the procedure given above. Table I1 shows that the procedure permits the quantitative separation of added titanium from 10 to 20 times as much rnolybdcnum or vanadium. Table 111. Quantitative Recovery of Titanium Added to Steel Sample Titanium Added, Mg. 0 00 0 25 0 50
Titanium Found, Mg.
Difference,
0.00 0.27 0 50
0.00 0 02
Mg.
0 00
ASALYSISOF STEEL. A stock solution of a stainless steel containing 25% chromium, 18%nickel, 2% manganese, 0.2% molybdenum, and 0.2%copper was pre ared by dissolving 1.0 gram of steel shavings in 20 ml. of 1 to 1 Rydrochloric acid and evaporating to dryness on the steam bath. The residue was leached with 10 ml. of hydrochloric acid and 30 ml. of water, and the resulting solution was heated to boiling and filtered into a 100-ml. volumetric flask. The filtrate was then cooled and diluted to volume. Ten-milliliter aliquots of the steel stock solution were placed in each of three 15-ml. centrifuge tubes; 0, 0.25, and 0.50 ml., respectively, of the standard titanium solution were added to the centrifuge tubes, and the titanium content was determined according to the procedure. The results given in Table 111 show that the added titanium was satisfactorily recovered. Analysis of Standard Steel Samples. The procedure was used to analyze two National Bureau of Standards certified steel samples, XBS-121B and XBS-170, and several Type 309 stainless steel samples, t o which known amounts of titanium were added. Two 10.0-ml. aliquots of each of the Type 309 stainless steels were used. In each case the first aliquot was analyzed without the addition of titanium, and the second aliquot was analyzed after the addition of the amount of titanium shown in Table IV. DISCUSSION
Table I. Ti Taken, Mg. 0.25 0.50 0.75 1.00
Table 11.
Quantitative Recovery of Titanium
Absorbance From standard curve B y 0.151 0.300 0,442 0.608
procedure 0.170 0.286 0.441 0.574
Ti Recovered. M g . 0.28 0.48 0.73 0.96
Preliminary experiments in this laboratory indicated that only 75 to 80% of the titanium was coprecipitated with one precipitation of zirconium arsenate. Further investigation showed that a quantitative separation could be achieved by precipitating zirconium arsenate twice.
Quantitative Recovery of Titanium in Presence of Molybdenum and Vanadium
Titanium Taken,
hlolybdenuin Added.
Vanadium Added.
Titanium Recovered,
Mg.
Mg. 10.0 10 0
Mg.
Ma.
, . .
10.0 10.0
0.50 1.00 0.50 1.00
...
...
Table IV. Sample
Analysis of Steel Samples
Composition of Steel, % Essential elements other t h a n iron
Titanium .4dded, ?&
0.51 1.04 0.52 1.00
1’1 epare the standard titanium curve by pipetting 0.28, 0.50, 0.75, and 1.00 ml. of the standard titanium solution into separate 25-ml. glass-stoppered graduates. Dilute the solutions to 25.0 ml. with 10 volume % sulfuric acid and develop the color as indicated above. Plot absorbance against milligrams of titanium per 25 ml. EXPERIMENTAL
Quantitative Recovery of Titanium. COPRECIP~TATIOS WITH ZIRCONIUM. The quantitative recovery of titanium when zirconium was precipitated as the arsenate was verified with known amounts of titanium, with the results shomm in Table I.
a
b
Certified titanium value for NBS-121B = 0.416’%. Certified titanium value for NBS-170 = 0.23%.
Titanium Found,
1904
A I ~ A L Y T I C A LC H E M I S T R Y
The procedure given above is suitable for the analysis of steels haling a titanium content of 0.05 t o 1.0%. httempts t o extend the lowrr limit by taking a 5-gram sample were unsuccessful because the increased concentration of the steel components in the same volumes given in the procedure appeared to retard the coprecipitation of titanium. Howevcr, the sensitivity of t h r present procrdure can probably be increased five to 10-fold by cmployng 5- or 10-em. cells in the Beckman spectrophotometer instc>adof the 1-em. cell uscd in the procedure. A reagent blank should br run on all rcagents, particularly the zirconium sulfate J?xperience indicates that the zirconium d t s may uften cont:tin significant amounts of titanium, a-hereas the other reagents are gencrally free of titanium.
LITERATURE CITED
(1) Fefgl, F., and Rajmann, E., M i k r o c h m i e , 19, 60-3 (1935). (2) Klinger, P.,and Koch, W.,Arch. Eisennhilttenw., 13, 127-34 (1939). (3) Lundell, G. E. F.. Bright. TI. h.,aad Hoffman, J. I., “Applied Inorganir .-\iidy$is,”2nd ed., New York, John Wiley PE Sons, 1953. (4) hIerwin, H. E., A m . J . Sci., 28, 119 (1909). Acta, 9, 324-9 (1953). (5) Pickering, R7.F., .4naZ. Chi???. (6) Pribil, R., and Schneider, P., Chem. Listy, 45,7-10 (1951).
(7) Sandell, E. B., “Colorimetric Determination of Traces of hletals,
2nd ed., New York, Interscience Publishers, 1950. (8) Slawik, P., Chem. Ztg., 34, 368 (1910). (9) Thanheiser, G., and Goehbels, P., Miu. Kaiser-Wilhelmlitst. Eisenforsch.Dilsseldorf, 23, 187-94 (1941). (10) Weissler, A., IND. E m . CHEM.,~ ~ N A LED., . 17, 695-8 (1945). RECEIVED for review ,July 12, 19.3. Accepted September 13, 1954.
Analysis of Lubricating Oil by Thermal Diffusion and Mass Spectrometry F. W. MELPOLDER, R. A. BROWN, T. A. WASHALL, WILLIAM DOHERTY, and W. S. YOUNG The Atlantic Refining Co., Philadelphia, Pa. 1
An analytical study was made to determine the effectiveness of the thermal diffusion process for the separation of a light lubricating oil into specific hydrocarbon types. Sixteen different hydrocarbon types were identified and determined in the thermal diffusion fractions by mass and ultraviolet spectrometry. The thermal diffusion process was shown to concentrate cycloparaffinsaccording to number of rings, isoparaffins, and n-paraffins. A lower degree of separation was obtained for the aromatic hydrocarbons.
T
HE recent development of liquid thermal diffusion has provided a new and effective means for separating petroleum stocks into specific hydrocarbon types. The method was investigated extensively by Jones and coworkers (7, 8 ) , who found that lubricating oil fractions of high viscosity index could bc obtained, and that thermal diffusion was equally applimble to naphthas, Taxes, and highly viscous oils. Separations b e h e e n isomeric compounds were made as well as separations of ring structures from aliphatic compounds. The work of Jones and coworkers har demonstrated clearly the versatility of the thermal diffusion process. I n the work described an attempt was made to study the effectiveness of this procesfi for the separation of mnnv specific types of hydrorarbons from light lubricating oil. To do this mass spectrometric analyses were made of a series of fractions from a batch type of liquid thermal diffuqion separation. A total of sixteen different hydrocarbon types m r c identified and determined APPARATUS
Thermal Diffusion Columns. The thermal diffusion column of the type designed by Jones (8) was 8 feet tall and 0.637 inch in mean diameter, and had an annular slit of 0.012 inch. The volume of this annular spare u-as 36 ml Seven ports were evenly distributed over the column from top to bottom for removal of fractions. Tap water was circulated through the inner tube from the bottom to the top of the column. The outer tube was evenly wrapped with electric. heater wire to provide a 3000-n-att heat input. Three iron-constantan thermocouples were silversoldered to the outer tube a t the top, center, and bottom of the column. A high limiting Siniplytrol pyrometer was used to protect the column against overheating in the event of failure of the water supply. The column was modified for hittch operation to obtain greater efficiency. To do this an external rrservoir of 200-ml. capacity was placed a t the top of th? columri and attached to the t x o ippeiI
most take-off ports as shown in Figure 1. Oil in the reservoir was circulated through the upper portion of the column by means of a nitrogen gas lift, and was thus maintained in equilibrium with oil in the top section of the column. Obviously, no fractionation by thermal diffusion occurred in this portion of the column. Fractions were withdrawn continuously from the bottom of thc column at rates varying from 2.5 t o 5 ml. per day. A micropump designed for this purpose (Figure 2) consisted of a glass syringe in which the plunger was connected to a worm drive turned by a clock motor. By changing the size of the glass syringe and clock motor speed, the rate of withdrawal may be varied from 1 to 50 ml. per day. However, optimum separations occurred a t the lower n-ithdrawal rates of about 2.5 ml. per day. Mass Spectrometer. A Consolidated Engineering Corp. 21-103-4 mass spectrometer \vas modified for the analysis of compounds of high molecular weight. A heavily insulated m:ignet was operated a t high flux to focus the ions of high masses. In order t o improve resolution, the analyzer slit width was reduced from 30 mils to 5 mils. .-in internally heated sample inlet tube to the ion source was supplied by Consolidated. A sample inlet system, built to operate a t 680’ F., consists of a 2-liter borosilicate glass bottle placed in an insulated rectangular oven made of stainless steel and Transite. Heat is supplied by four 500-watt wire coil heaters which are supported on the inside of the oven by Insulute cement (manufactured by The Sauereisen Cements Co., Pittsburgh 15, Pa.). Connected to the bottle is a glass leak, which in turn joins the heated cover plate through a glass linr Wrapped around the leak and leak line is a wire heater. This systeni is shown in Figure 3. A molten tin cutoff valve separates the inlet system from vacuum pumps. A valve described previously (IO) for this purpose used gallium. Because gallium wets glass and is expensive, various substitutes were tested and tin was found to be more desirable in both respects. Even though tin has the undesirable property of a much higher melting point (450’ F.), this is well below the operating temperature of 680” F Figure 1. Diffusion Tin is chemically active and asColumn sumes a dirty nppearancc Litter
