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
V O L U M E 26, N O . 1 2 , D E C E M B E R 1 9 5 4
190s
from the column with 3 liters of isohexane. The aromatics were then demrbed with a mixture of bensene and isopropyl alcohol. Solvent was removed by evaporation at room temperature. Last traces of solvent were stripped from the oil with a stream of nitrogen gas. The two oil fractions, 310 ml. of saturates and 90 ml. of aromatics. were then suhiected senaratelv to thcrmal diffusion. The thermal diffusion colunm was charged by forcing ail from a glass syringe into the bottom port until the oil appeared in the reservoir a t the top. The remainder of the oil charge was then placed in the reservoir. Ciroulation of oil through the reservoir
Figurc 2.
\Iieropirmp
some use. Extensive tests ehoacd, however, that it did not cause natioeahle hydrocarbon decomposition nor contaminate the sample. Samples are introduced through a gallium-sealed sintered disk kept a t 680' F. Two techniques have been used to meter known amounts of sample to the sv8tem. One of these, the microhuret
kading until the buret and sample re&&ning in it hive cooled to approximately room temperature. The-second technique employs a metering valve assembly (4), which is applicable to Goand liehter comnounds. I n uractice. the meterine valve is kolated h m the Lain sample &tern b y a tin cutoff v&e and is used primarily to check sensitivity measurements. I t is a h useful for introducing samples of inordinately high melting points or ones which sublime. Ultraviolet Soectrouhotometer. A Be ckman DU spectrop hotometer was usid to scpplement the ma88 spectrometer.
the ~&ffinic &%ion w& cdarged and 8 lower withdrawal rate of 2.5 ml. per day was established. A total of 32 fractions were collected in about 7 weeks. The composition of all fractions w a s then determined by calculation of mass spectral and ultraviolet absorption data. METHOD OF CALCULATION
Spectra have been obtained for more than 100 pure hydrocarbons in the Ca to CWmolecular weight range. Mont of these were supplied by API Project 42 a t Pennsylvania State College for measurement of their mass spectra. A study of these SlJeCtL2. indicated the feasibility of a hydrocarbon-type ranaly8ia method applicable to the lubricating oil range. Such a method was devised as an extension of the compound type analysis methods already applied to petroleum naphthas and heating oil distillates ( d , 3). Lubricating oil analysis is vastly more complex, because of the larger number of possible compound types. O'Neal has discussed a similar method oi :m:ilyris (9).
S 3
by Be& and Doeksey
u t from a mixed crude
-
:ht lubricating oil for twn in Table I. Thin Figure 3. Sample-Inlet S . nd dehydrcycyclic ight of '1:able 11. Peaks Used in Hydrocarbon-Tyy ,e Analysis ranged component Peak Sumolation 71
67
small hydrcomstie ica gel hemal ish heFour hrough ~.filled &son
++ 8568 t- G9 + 81 + 82 + 83 + g n + 97 + 124 + 1.17 + 138 + 151 f 152 + . . etc. + 150 + 163 + 164 t 177 + 178 + . . etc. + 217 + 218 + . . etc. + 190 + 203 + 204
123 149 189 229 269
+ 230 + 215 + + 217 + 258 + . . stc. 284 + 207 + 298 + . . eto. ++ 270 + 283 + 244 142 + 115 + 156 + 160 + 170 + . . + 158 + I 7 1 + 172 f 185 + 186 t . . etc. 153 + 154 + 187 + 108 t 181 + 182 + . . etc. 151 + 152 + 105 + irin + 179 + 180 + . . etc. 177 + 178 i 101 + 192 + 205 + 206 + . . etc. 91 + 92 + 105 + 10G + 119 + 120 t . . I75, + 176 I17 + 118 + 131 + 132 + 145 + 148 + . . 215 + 141 157
ee. etc.
ied tricydoaromatios F""h
216
CtD.
ANALYTICAL CHEMISTRY
1906 Table 111. Aromatic Fractions (Volume per cent) Dihydronanhthalmm ~~~~~~~and/or Dicycloparaffin Condensed Free Benzenes (ConAryl CycloNaphthyl densed Tricyclic) paraffins 0.32 0.25 0.10 0.27 0.23 0.10 0.29 0.24 0.10 0.27 0.23 0.09 0.34 0.31 0.11 0.48 0.19 0.43 0.42 0.35 0.18 0.52 0.35 0.24 0.60 0.33 0.30 0.62 0.29 0.37 0.54 0.23 0.41 0.36 0.16 0.36 5.03 3.40 2.55 ~~~
Fractions 1 2 3 4 5 6
Tricyclics 0.22 0.26 0.25 0.27 0.36 0.48 0.42 0.26 0.18 0.09 0.04
7 8 9 10 11 12 Total 2.84
0.01
Fluorenes 0.20 0.25 0.25 0.25 0.32 0.42 0.29 0.26 0.20 0.15 0.09
0.05
2.73
Biphenyls and/or Acenaphthenes 0.20 0.20 0.19 0.21 0.29 0.40 0.32 0.28 0.23 0.17 0.12 0.06 2.67 _ .
.~~
~
~
Free Phenyl 0.11 0.09 0.08 0.08 0.09 0.14 0.11 0.18 0.25 0.40 0.66 1.09 3.28
% Total
Sample 1.40 1.40 1.40 1.40 1.82 2.54 2.09 2.09 2.09 2.09 2.09 2.09 22.5
ent peaks serve to resolve the mono- from di- and tricyclics and to determine the molecular weight distribution of hydrocarbon types. By making use of these techniques it is possible to resolve the following compound types (where types are defined by structures containing aromatic or cycloparaffinic rings, i t is assumed the rings may have other substituents).
Normal paraffins. m.s. type analys-is and parent pesk calculation. 2. Isoparaffins, m.s. type analysis and supplementary data from dissociated ions. RIonocycloparaffins, m.s. type analysis and parent peak calculation. a, ~ i ~ ~ (noncondensed) ~ l ~ ~ grouped ~ ~ ~ f f i by m's' type b. Tricycloparaffins (noncondensed) c. Tetracycloparaffins (noncondensed) Dicycloparaffins (condensed), m.s. type analysis. Tricycloparaffins (condensed), m.s. type analysis. Tetracycloparaffins (condensed), m.s. type analysis. Pentacycloparaffins (condensed), m.s. type analysis. Hexacycloparaffins (condensed), m.s. type analysis. Free naphthy1s, m.s. a. Dihydronaphthalenes '(grouped by b. Dicycloparaffin benzenes (condensed tricyclic)/ m.s. analysis. a. Acenaphthenes grouped by m.s. b. Biphenyls (structure is +Cn-+. n 2 I)} type analysis. a. Acenaphthylenes grouped by n1.s. type analysis b. Fluorenes Condensed tricycloarolnatics a. Phenanthrenes grouped by m.s. type analysis, resolved by b. Anthracenes ultraviolet. 1.
The practical limit to the number of hydrocarbon types which 3. can be resolved in a given mixtureis approximately ten. hi^ is based on the fact that hydrocarbons, in general, have major 4, ions which occur in a series corresponding to masses of molecular weight and molecular weight minus one or as dissociated frag6. mentsof low mass. As each series is summed up to obtain one 6. combined peak to a particular type, and hydro7. carbons occur as a homologous series separated by fourteen mass 8. 9. units, two of each group of fourteen possible peaks are necessary to define a hydrocarbon type. This limits t o seven the number lo. 11. of constituent hydrocarbons to be resolved in the parent mass region. Aliphatic paraffins and noncondensed cycloparaffins 12. have intense ions of low mass and so can be determined independently. Some exceptions exist to the limit of seven imposed by 13. the parent mass region. Thus, condensed four-ring aromatics 14. such as pyrene and fluoranthene of molecular weight 202 occur in the same series as indans and Tetralins, which start a t much 15. Free lower molecular weights (118, 132). Since the major ions of the a. Alkylbenzenes tetracyclics occur at 202 or above, these compounds can be at b. Diphenyls (structure is +-Cn-+, n > 1) grouped by m.s. least partially resolved from indans and Tetralins, whose most type analysis. c. Phenylcyclo2araffins (structure is + - C r 13, 71 2 1) intense ions have masses less than 202. A similar situation grouped by 16. a. Indans exists in the case of four-ring condensed cycloparaffins and benm.s. type b. Tetralins zenes. Some of this ambiguity was not encountered in this work, analysis. c. Phenylcycloparaffins (structure is Q - 2 ) as ultraviolet absorption data indicated pyrenes and fluoranthenes were absent. Table IV. Paraffin-Cycloparaffin Fractions The number of compound (Volume per cent) types determinable in a mixNoncond. ture can be essentially doubled Condensed Paraffins PolyMonoIsoFree Hexa- Penta- TetraTriDicyclocycloparafNormal % Total by separating a into Fractions Phenyl cyclic cyclic cyclic cyclic cyclic para. para. fins Para. Sample paraffinic and aromatic frac1 0.24 0.01 0.12 0.44 0.56 0.30 0.19 ... ... ... 1.86 2 0.25 0.04 0.34 1.05 0.82 0.44 0.01 ... ... 2.95 tions prior t o mass spectro3 0.14 0.01 0.05 0.84 1.14 0.57 0.12 ... ... 2.87 4 0.10 0.01 0.60 1.22 0.65 0.13 ... ... 2.71 metric analysis. Also, for ex5 0.06 0.43 1.42 0.80 0.47 . , .., 3.18 ample, ultraviolet absorption 6 0.02 0.21 1.29 0.88 0.78 ., . ... 3.18 7 0.01 1.09 0.59 1.18 ... ... 2.87 can be used t o resolve anthra8 1.08 0.50 1.57 0.11 ... 3.26 9 0.63 0.23 1.73 0.51 ... 3.10 cenes and phenanthrenes which .., 2.95 10 0.44 0.08 1.49 0.94 are grouped by t'he mass 11 0.24 0.09 1.25 1.68 , . . 3.26 ... 3.02 12 0.10 0.05 0.98 1.89 spectrometric method. 13 0.02 0.08 0.92 1.95 ... 2.95 14 0.06 0.99 1.74 ... 2.79 As in most cases individual 0.04 1.14 1.61 ... 2.79 15 compounds cannot be resolved 16 0.04 1.09 1.35 ... 2.48 3.18 17 1.49 1.54 0.15 because of the complexity of 18 1.42 1.29 0.24 2.95 19 0.78 1.41 0.99 3.18 the sample, the most reliable 20 0.10 0.34 0.72 1.16 information obtained is based 21 0.09 0.40 1.25 1.74 22 0.02 0.25 1.47 1.74 on type analysis. It is feasi23 0.01 0.16 1.57 1.74 24 0.01 0.08 1.65 1.74 ble, however, t o use parent 25 0.05 1.69 1.74 26 1.73 1.73 peaks to resolve some com27 1.73 1.73 pound types. Thus, accord28 1.73 1.73 29 1.73 1.73 ing to type analysis, mono-, 30 1.73 1.73 31 1.73 1 .73 di-, and tricyclic noncon1.73 1.73 32 o.82 - -_ - - - d e n s e d cycloparaffins a r e 0.01 0.18 0.83 3.69 9.79 5.29 17.77 17.30 21.84 77.5 grouped. I n this case par-
1
}
~
-
~
~
V O L U M E 26, NO. 12, D E C E M B E R 1 9 5 4 Table V.
Fraction 1 2 3 4 5 6 7 8 9 10 11 12
1907 tions of tricyclic aromatics, acenaphthenes, flucrenes, and dicycloparaffin benzenes decreased steadily to a minimum in fraction 12. Free naphthyls reached a maximum in fraction 10, then deAlkylbenzenes creased. Similarly, condensed aryl cycloparaffins 246 reached a maximum in fraction 11. Free phenyls 240 239 rose quickly to a relatively high concentration in 245 fraction 12. 241 232 In Table IV the results of the paraffin-cyclo234 233 paraffin run show that a consistent separation oc236 curred. The first types to show maximum con250 251 centrations were the four-, five-, and six-ring 256 condensed cycloparaffins in fraction 1. Threering condensed cycloparaffins and free phenyls reached their maximum in fraction 2. The presence of free phenyls in this paraffinic fraction is due to the failure of silica gel to remove the aromatic material completely. All the hydrocarbons mentioned above decreased rapidly in concentration to zero a t or before fraction 8. Condensed dicycloparaffins increased in amount to a maximum in fraction 5, then decreased to zero in fraction 14. Noncondensed polycycloparaffins reached a maximum in fraction 6 and decreased to zero concentration in fraction 17. Monocycloparaffins show two maxima a t fraction 9 and fraction 17. This may be due to a greater degree of substitution on the ring in the earlier fractions as compared with later fractions. The monocycloparaffins then decreased to zero concentration in fraction 25. Isopara5ns first appeared in fraction 8, reached a maximum in fraction 13, then decreased to zero in fraction 26. *Paraffins were first found in fraction 17 and then rapidly increased to 100% in fraction 26. Only n-paraffina were present in fractions 26 through 32. The average molecular weights of the hydrocarbon types present in the aromatic portion are seen in Table V and in the paraffin-cycloparaffin portion in Table VI. I n most cases the higher molecular weight members of the series were removed first from the bottom of the column, as would be expected. However, for the aryl cycloparaffins and alkylbenxenes in the aromatic portion the reverse was found to occur, with the members of lighter molecular weight appearing in the first fractions.
Mean Molecular Weights Calculated for Compounds in Aromatic Portion
Tricyclic Aromatics 245 220 219 215 211 199 190 194 193 190 189 179
Fluorene6 255 22 1 222 217 211 205 202 196 194 188 170 166
Biphenyls and/or Acenaphthenes 231 223 223 218 214 211 203 204 199 193 192 188
Alkyl Naphthalenes 248 227 229 225 218 212 202 194 185 182 183 181
Aryl Cycloparaffins 222 218 217 216 212 211 218 233 237 254 246 245
The peaks used in the hydrocarbon-type analysis are tabulated in Table 11. According to the outline, sixteen compound types or groups can be determined. Some ambiguity exists in the scheme, as may be noted. Biphenyls (No. 12b) and diphenyls (No. 15b) are members of the same class of compounds but owing to structure effects have distinctly different mass spectra. The principal ion in the spectrum of diphenylmethane (d CHz+)+ occurs a t its parent mass, whereas d CHzCHz d dissociates to yield a (d CH2)+ ion. This latter ion is typical of an alkylbenzene and not the biphenyl ion which is defined. This accounts for the arbitrary classification of bi- and diphenyls. Phenylcycloparaffins show a similar structure effect, although it is not so pronounced. h compound such as 6 CHz 3 dissociates to yield an alkylbenzene ion, (6 CH3)+, but phenylcyclohexane (d - ) ; 1 has its most intense ion a t mass 104, corresponding with a Tetralin. Phenylcyclohexane also has an intense alkylbenzene ion a t mass 91, EO that according to type analysis this sort of compound behaves most like a Tetralin but is also similar to an alkylbenzene. Because dissimilar compounds 15a, 15b, and l5c possess similar spectra, causing them to be grouped in the mass spectrometric analysis, >hey are designated in a single class as free phenyls Consideration of naphthalene ring compounds showed also the) should be called free naphthyls rather than simply naphthalenes. In this calculation some hydrocarbons which may be present in minor amounts are not considered. Included in this group are aliphatic olefins (5, 6) and some of the partially hydrogenated polycyclic aromatics (9). The thermal diffusion fractions of the aromatic portion of the oil and fractions 1 to 14 from the saturate portion were calculated according to the compound type analysis procedure. Parent peak calculations and ultraviolet absorption were also applied. Saturate fractions above No. 12 were calculated using the wax analysis procedure of O’Neal and Wier (10). In the paraffin fractions the contribution of isoparaffins to monocycloparaffinic peaks (C,H,,) was assumed to be 50% of isoparaffinic peaks a t CnHZn+lmasses. Peak sensitivities were assigned in the ratio 1 :3.0: 1.5 for normal, isoparaffins, and monocycloparaffins, respectively, based on calibration data of compounds similar to those suspected of being present. ANALYSIS O F THERMAL DIFFUSION FRACTIONS
The results of the analysis of the aromatic portion are given in Table 111. The analysis shows only a small degree of separation in the first seven fractions. All of these fractions were of high viscosity and therefore would not be as readily fractionated as less viscous oil. I t is apparent from this that additional time is required for the sample in the reservoir to come to equilibrium with the sample in the column and that a substantially lower rate of withdrawal should be used for the more viscous fractions of an oil. However, a definite separation was obtained for fractions 8 through 12. This may be due to the fact that the last fractions were withdrawn from the side ports of the column after several days of operation following removal of fraction 6. Concentra-
CONCLUSION
The evaluation of the thermal diffusion process has shown that the following hydrocarbon types may be concentrated to varying
l’able VI. Mean Molecular Weights Calculated for Compounds in Paraffin-Cycloparaffin Portion Fraction 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
91kyl Benzenes 275 275 251 242 250 250
Tricycloparaffins 271 269 266 244 237 240 243 243 237 235
Dicycloparaffins 287 277 273 271 241 234 257 250 238 246 246 236 24 1 240
Monocycloparaffins
Normal Paraffins
...
268 254 260 284 285 280 263 257 259 258 255 254 251 252 245 230 220 217 200 185 210
276 288 304 300 300 29 1 288 282 278 276 272 268 264 261 258 257
1908
ANALYTICAL CHEMISTRY
degrees, provided P prior separation of paraffins and aromatics by silica gel is employed.
five-, and six-ring condensed cycloparaffins, noncondensed cycloparaffins, monocycloparaffins, isoparaffins, and n-paraffins.
n-Paraffins from isoparaffins. 2. Isoparaffins from condensed cycloparaffins. 3. Monocycloparsffins from noncondensed di- and tricycloparaffins. 4. Condensed dicycloparaffins from condensed polycycloparaffins. 5 . Free phenyls from aryl cycloparaffins and polynuclear aromatics. 6. Aryl cycloparaffins and free naphthyls from biphenyls, fluorenes, and tricyclic aromatics.
(1) Beale, E. S. L.. and Docksey, P., J . Inst. Petroleum, 2 1 , 860 (1935). (2) Brown, R. 4., .&NAL. CHEM., 2 3 , 4 3 0 (1951).
LITERATURE CITED
1.
Very little separation was obtained between isoparaffins and monocycloparaffins. This is believed to be due partially to the molecular weight range of the oil. As a result of the separations by both silica gel adsorption and thermal diffusion, the mass spectrometer analysis was able to resolve 16 different molecular compound species. These include tricyclic aromatics, fluorenes, biphenyls and/or acenaphthenes, free naphthyls, dihydronaphthalenes and/or dicycloparaffin benzenes, aryl cycloparaffins, free phenyls. two-, three-, four-,
(3) Brown, R. A , Doherty, W., and Spontak, J., Consolidated Engineering Corp., Pasadena, Calif., Group Rept. 84 (1951). (4) Brown, R. A . , Xielpolder, F. W., and Young, W. S., Petroleum Processing, 7, 204 (1952). (5) Fred, RI., and Putscher, R., ANAL.CHEM..2 1 , 901 (1949). (6) Haak. F. rl., and Van Nes, K., J . Inst. Petroleum, 37, No. 329, 245 (1951).
(7) Jonea, 9. L., Petroleum Processing, 6, 132 (1951). ( 8 ) .Jones, A. L., and Llilberger, E. C., Ind. Eng. Chem., 45, 2689 (1953). (9) O’Keal, 51. J., Jr., “Application of High ~lolecularWeight
Mass Spectrometry to Oil Constitution,” Conference on ;Ipplied Mass Spectrometry, London, England, Oct. 2 9 and 30. 1953.
(10) O’Neal, hi. J., Jr., and \Tier, T. P., Jr., ANIL. CHEM..2 3 , 830 (1.9.51). .._ (11) Taylor, R. C., and Young, 1 7 , 8 1 1 (1945). I .
R. S.,IND.ESG.CHEM.,ASAL. En..
RECEIVED for review May 24, 1954. .Iccepted September 27, 1954. €’re sented at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, hlarch 4, 1953.
Ion Exchange Method for Determination of Alkali Metals in Presence of Calcium and Magnesium OLOF SAMUELSON and E E R O S J a S T R 6 M Department o f Engineering Chemistry, Chalmerr Teknirka Hb’gskola, Gothenburg, Sweden
; irapid and accurate method has been evolved for deter-
mining potassium, sodium, and lithium in the presence of calcium and magnesium. The method is based upon the ability of ethylenediaminetetraacetic acid (EDTA) to give stable chelates with calcium and magnesium in water-ethyl alcohol solutions. The bivalent metals are taken up in a column filled with a mixture of an anion exchange resin in the ethylenediaminetetraacetic acid form and the acetate form. The alkali metals appear in the effluent which is passed directly through a second column containing an anion exchanger in the free-base form. The alkali hydroxides obtained in the effluent after the second column are titrated with standard acid. The determination can be carried out in less than 2 hours.
A
SIMPLE ion exchange method for the determination of
sodium and potassium in the presence of vanadium, iron, copper, nickel, and cobalt has been devised by Samuelson and Schramm ( 4 ) . The solution is passed through two columns coupled in series; the first column is filled with an anion exchanger in the citrate form and the second n-ith an anion exchanger in the freobase form. The alkali metals pass through the first column as citrates, whereas the other metals are transformed into citrate complexes which are strongly held by the resin. I n the second column the citrate ions are exchanged for hydroxyl ions. AMter washing the columns with water the alkali metals can he determined quantitatively by titrating the effluent x i t h standard acid. The separation can be performed in 1 to 2 hours and the accuracy is within about f 0 . 2 % . Calcium and magnesium have been found to behave largely in the same manner as the alkali metals (3). I t should be of considerable interest to work out a similar procedure for the removal of
calcium and magnesium from solutions containing the alkali metals. 9 certain uptake can be achieved by working a t high pH with resin in the citrate form but the complexes are not strong enough to permit a quantitative separation. Ethylenediaminetetraacetic acid (EDTA) is known to give more stable chelates with calcium and magnesium than citric acid and therefore complete uptake might be obtained using anion exchangers in the ethylenediaminetetraacetic acid form. However, when working with aqueous solutions, calcium and magnesium rn ere only slightly retarded in the column. Because the stability of the ethylenediaminetetraacetic acid chelates increases with an increase in pH, a mixture of resin in the ethylenediaminetetraacetic acid form and the freebase form would be expected to be more effective. This was confirmed by a series of experiments carried out as a combined batch and column operation. Under proper conditions a quantitative uptake could be obtained but when working n i t h a moderate excess of resin it was observed that, on washing with Tater, traces of calcium and magnesium appeared in the effluent. Ion elchange experiments carried out in the present investigation showed that the uptake of calcium and magnesium by the resin is much more effective in an alcohol-water solution than in pure water. The alkali metals are not taken up and can be displaced from the column by nashing with the solvent. I n this mannei it is possible to separate calcium and magnesium quantitatively from potassium, sodium, and lithium. In a second column the alkali salts are converted into hydroxides which arc’ determined by titration u ith standard acid APPAR4TUS
I t is important to have a resin of good chemical stability. The strongly basic resin Dowex 2 wa? used in the present investigation. I t is desirable not to have too long a time of contact between the resin and the solution 4n appropriate flow rate was obtained when the particle size of 0.30 to 0.54 mm. was used.
