Like Golubtsova, Anderson prepared analytical curves by carrying standards through the entire procedure. TO check for volatilization losses, he did the same with a known synthetic solution. Obtaining correct results from standard samples and synthetic solutions, he concluded that boron did not volatilize during this treatment, As in Golubtsova's case, however, the only justifiable inference from these results would seem to be that the fractional losses, if anyI were equal as between samples and standards. To determine whether volatilization losses had actually occurred, the relevant portions of Anderson's procedure were repeated. One thousand micrograms of boron as &BO8 solution were treated with 6 ml. of concenlrated HC104, 3 ml. of concentrated " 0 8 , and 1 ml. of IP&. This mixture was then used to dissolve 0.3095 gram of CuO. The resulting solution was fumed dry and the residue baked 10 minutes a t 400' C. A second solution, similar to the others but without copper, was also subjected to the fuming and baking procedures. After the residues had cooled, 0.3095 gram of CuO was added to the second residue; both residues were dissolved in 1% HzSOd, treated with 1000 pg.
of Go (as internal standard), and made up to 10.00 ml. A control Bolution was prepared by dissolving 1000 pg. of B, 1000 pg. of Co, and 0.3095 gram of CuQ in 10.00 ml. of 1% HzSQ4. The three solutions were analyzed for boron by the carbon porous cup technique, as described above. The sample which had been fumed and baked in the presence of copper retained 45.0% of its boron. The sample which had been fumed and baked without copper retained only 2.4%. Thus more than half of the boron was lost, even when the copper salt was present. If the success of an analytical procedure calibrated with known samples s to be taken as proof of the validity of an underlying assumption, (e.g., the nonvolatility of boron at elevated temperatures) the proof must be both necessary and sufficient. I n this case, the nonvolatility of boron was not actually a necessary condition for the success of Golubtsova's and Anderson's procedures; to give correct results, these procedures required only that the fraction of boron lost be reproducible from one analysis to the next. Their inference of nonvolatility was thus unjustified on the basis of their own evidence and apparently incorrect
on the basis of ours. These procedures give correct results when performed with due consideration of the nature and behavior of the variables involved. It is important, however, that the physico-chemical behavior of the system be known as fully and accurately as possible so that the propagation of errors in future work may be avoided. ACKNOWLEDGMENT
The author expresses his gratitude to Hisashi Kubota for performing the titrations mentioned in the text. LITERATURE CITED
(1) Anderson, R. F., Appl. Spectroscopy 14, 123 (1960). (2) British Iron and Steel Research Association, J. Iron Steel Znst. (London) 227-32 (1958). (3) Golubtsova, R. R., Zhur. Anal. Khim.
15,481 (1960). (4) Levi, G. R., Curti, R., Gam. chim. ital. 6 8 , 376 (1938). (5) Spicer, G. S., Strickland, J. D. H., Anal. Chim. Acta 18, 523 (1958). (6) Tchijewski, P., Arch. Phys. Nut. (3) 12, 120 (1884). (7) Wakamatsu, S., Japan Analyst 7, 309 (1958).
RECEIVEDfor review June 28, 1961. Accepted July 24, 1961.
%e aration by
ent #or Continued ~
R C. AALDERWEIRELDT ~ ~
iaborafory o f Organic Chemistry, University o f Ghenf, Ghenf, Belgium The technique discussed permits e continued separation of binary mixtures in a batchwise countercurrent flow of two immiscible solvents. The practical and versatile instrument described uses the principle of separate stages or cells. Ita main features are the possibility of stopping the sepacontrol analyses without ecfs and possible use even for tow 0 values ( a 1 . 2 as limit). The technique was tested on cresof mixtures and on hops alpha acids. It should find application on all mixtures which can be separated by extraction and when larger amounts 0%the sw~st~nces are needed, such as ~ ~ n ~ h emixtures, s~s natural products, rare eurths, and atomic fission material. QNTIMUOUB separation
of mixtures by liquid-liquid extraction hae received much attention lately and existing methods have been described
extensively by Scheibel (8). Research to carry out such separations in a cell train of the Craig type with both phases moving in opposite directions has been in progress for several years in this laboratory. Two cell models have been described (IO, IS), but improvements still seemed necessary. We now report on an apparatus with a new and entirely satisfactory cell design, provided with the necessary filling and outflow devices and driven by a robot with the desired possibilities. We propose the name "steady-state distribution" (S.S.D.) for the separations as obtained with such an instrument. The cell design is shown in Figure 1.
A and C are calibrated to 20.0 f 8.1.ml. The phases are mixed in part A - B. The movements are: e uilibration of the phases by rocking getween -20' and 3-20"; demixing of the
phases in the horizontal position; transfer of the upper hase by turning 100" &ockwise), turnthe train to
-
ing back to +20° and then to the horizontal position; and transfer of the lower phase by turning the train to +11Q', back to -20', and then to the horizontal position. A train of 81 cells was mounted in two banks of 10 and 41, one above the other. The middle cell is numbered 0, the upper bank +1 to +40, and the lower bank -1 to -40. In this way cells 40 and -40 lie one above the other. The design of the necessary glassware parts for feeding the fresh phases and permitting outflow of the extracts is shown in Figures 2 and 3. The mixture-feeding pump (Figure 2) is activated automatically a t each transfer by a cam on the axis of the S.S.D. train. In Figure 3 X is the axis of the train. Turning to -100' and back, used up er phase flows from cell +40 to A ancfout of the train through olyethylene tube B. At the same time Fresh upper solvent flows from reservoir N into the calibrated delivery tube, 6, and from there into the train. Heavy
insert, 8,permits accurate calibration
of F.
The movements of the train are obtained with a robot provided with profiled cams which are turned on and off with a key system, in turn controlled by a drum such as the one used in automatic carillons. (A slightly improved model of this apparatus i~ manufactured by Quickfit, England.) THEORETICAL ASPECTS
Figure 1.
Cell model of apparatus
Upper. Side view of one cell, axis of rotation perpendicular to plane of paper lower. Top view of several cells, showing how they are connected. Axis lies in plane of paper in vertical direction Angler mentioned are those used in trigonometry
phase outflow and feeding occur when turning to +llO" and back, from cell -40 to D and out of the train through polyethylene tube E and from reservoir T to delivery tube F . The movable
The theory of continuous separation by batchwise extraction as studied extensively by Stene @),Scheibel (8), and others (3-6) is not adapted to the experimental conditions of steady-state distribution, and this has led us to a complete revision and further development of this theory (1). The following points are of practical interest. The method for deriving the equations is given by Alderweireldt (I), I n ideal circumstances a steady-state distribution has the aspect of Figure 4. To obtain this result the partition coefficients, K A and KB, must be inde-
pendent of concentration changes and Equation 1 d
m
-
1
(1)
must be satisfied. I n this case upper, x , and lower, y, phase transfer follow one another in a 1 t o 1 ratio. I n the general case, where x and y are not equal, the steady-state concentration levels, LA and LB, are the fraction of A and B input as given by
At the other side of the feed cell the concentration drop occurs according to a geometrical series with a ratio (l/Ka)Z and (&,)e, respectively. More often the requirement ~ KX K A B = 1 cannot be met exactly and to keep a symmetric distribution pattern a slightly asymmetric transfer program has to be followed-the ratio g/x is not unity. This ratio is then given by d K a X KB =
(3)
Y/X
In practice the distribution is started with the assumption that d K A X K B
A
D
I
f
S
0 Figure 2.
Device for feeding mixture
A.
Stop with automatic air inlet 6. Stop to avold air pumping C. Valve to the cell train D. Reservoir E. Cam commanding pump M. Calibration of pump stroke
Figure 3.
Device for solvent feeding and outflow VOL. 33, NO. 13, DECEMBER 1961
e
1
Figure 4. sf 2.25
Idealized pattern for 2 1 -cell train and /3 value
KA KB
= =
0.67 1.50
CELL NUMBER
Figure 5.
will indeed be unity and with a program y/z = 1. As control analyses on the proceeding distribution eventually show a deviation from symmetry, the g/x ratio is slightly changed in the appropriate direction. Feeding of the mixture is carried out after each transfer of the upper or the lower phase. and the feed amount is determined by limitations in solubility and in stability of the partition coefficients at the calculated steady-state concentration. .4t the start, the concentration in and around the feed cell of a steady-state distribution with a chosen feed input as described, is much lower than the equilibrium steadyatate concentration. In order to attain the steady-state concentration more quickly, a special feed program called “forced feeding” is used. Equations to calculate such a forced feed program have been developed, but the details will be published elsewhere. Table I lists programs for the more usual 6 values. For practical separations this list should be considered only as a guide. The given values may be averagrd out over several transfers to minimizr the manual interventions.
A final point of theoretical interest is the efficiency of the apparatus, which can be calculated by Equation 4. (4)
fit,,, the theoretical p value, is obtained from the partition coefficients determined in the usual way-from batch equilibrations or fundamental countercurrent distribution (C.C.D.), for example. peXp,the experimental p value, is the one actually obtained from the S.S.D. apparatus and, may be determined from the partial concentrations in symmetrically placed cells from Equation 5. Amount of A in cell n Amount of A in cell - n X amount of B in cell amount of B in cell n = (@exP)2n (5)
CELL NUMBER
Figure 6 .
~
~
e
Steady-state distribution of = 2.34
~ istribution ~ ~ ~ of srn- and ~ ap-cresol ~ e fl = 1.49
+
+ “1
Figure 7.
0-
and m-cresol
SEPARATIONS
The apparatus was tested with cresol mixtures. I n a phase system of benzene and appropriate phosphate buffers the p value between 0- and m-cresol is 2.35, between 0- and p-cresol is 1.58, and between m- and p-cresol is 1.49. This is a good range, since separations with p values around 2.35 and higher are relatively easy, while a p value of about 1.49 constitutes a difficult problem. The general procedure consists in adjusting the phase system in such a way as to fulfill Equation 1. 4 certain number of transfers are carried outfor example, 30 upper and 30 lower. The separation is stopped and the concentration and relative amount of the substances are determined in two or more symmetrically placed cells. This shows whether the distribution is symmetric; if not, it gives the experimental partition coefficients and thus
Separation
by steady-state
dohumdone 0 Humulone (P = 2.21 X Adhumdone (13 = 3.3)
distribution
Figure 8. Analysis of symmetrical cells in cohumulone steady-state distribution
the correction in the y/x ratio to be introduced according to Equation 3. After additional transfers-for example, 60 and 66 with a y/x ratio of 10 to 11a new control is carried out. This procedure is repeated until corrections are no longer necessary. From this moment on the distribution can be carried on indefinitely. Cresol mixtures were analyzed by chromatography for 0- and m-cresol and by photometry for the other mixtures. Details of some interesting points in these analyses have been published ( 2 )*
S.S.D. separation of the mixtures was tested for lower (A3 mg. per cell) and for higher steady-state concentrations (&200 mg. per cell), In all cases the efficiency of the cells calculated with Equation 5 was 75 to 80%. The separation of 0- and m-cresol in low concentration and of m- and p-cresol in higher concentration is shown in Figures 5 and 6. To demonstrate the usefulness of the method in a general way we have applied the technique to the separation of cohumulone. Cohumulone is a constituent of hops alpha acid, which also contains humulone and adhumulone (7'). The composition of alpha acid was discovered by using C.C.D. and this method constitutes the only way to obtain pure co- and adhumulone. The amount of substance obtainable in this way is, however, restricted by the low solubility in the phase system used and by the labile nature of the natural substances, whirh are rspecislly srnsitivc to decomposition in the
Table 1.
Forced Feeding Program for Various Values of K, 1 / K , or
g. to be introduced in feed stage at each transfer to ohtain steadystate conrentration of 1 g. per cell)
(Feed quantity in Trans.fer KO. 0
2 4 6 8
10 12 14 16
18 20
_-
2.646 7 5000 3009 2614 2456 2377 2334 2307 2291 2280 2273
22
24 26 28 30 32 34 36 38 40 44 48 52 56 60 64 68 72 76 80 90 2257
P
-__
-
2.338
2.000
5
4
5000
5000
2865 2409 2214 2111 2048 2009 1983 1963 1950 1941 1933 1927
2779 2284 2065 1944 1867 1817 1780 1755 1737 1722 1712 1704 1697 1690 1687 1684
1910
1667
K or 1 / K Value 1.870 1.732 p Value 3.5 3 5000 5000 2730 2680 2314 2141 1892 1981 1746 1847 1652 1764 1587 1706 1538 1665 1502 1635 1612 1475 1453 1594 1435 1580 1420 1570 1410 1560 1399 1553 1391 1547 1384 1542 1379 1539 1374 1535 1369 1533 1365 1530 1360 1356 1352
+
1516
1340
1.580
~1.500 2.25
2.5 5000 2626 2063 1796 1638 1532 1457 1401 1357 1324 1296 1273 1255 1239 1226 1215 1204 1195 1189 1182 1176 1167 1159 1154 1149 1145 1141 1139 1137
5000
2800 2024 1748 1582 1470 1390 1329 1282 1244 1214 1188 1166 1148 1133 Ill9 1107 1097 1088 1080 1073 1061 1051 1043 1037 1032 1027 1023 1020 1018 1015 1011 1000
1126
(Continued)
VOL. 43, NO. 13, DECEMBER 1961
@
1923
NOMENCLATURE
K = partition coefficient.
M or 1/K Value
0 2 4 6 8 10 12 14 16 18 20 24 28 32 36 40 50 60 ‘70 80 90 100 120 140 160 180 200
248
280 320 360 400
1.450 1.414 1.378 1.341 1.304 1.265 1.225 p Value 2.1 2.0 1.9 1.8 1.7 1.6 1 . 5 5000 5000 5000 5000 5000 5000 5000 2584 2574 2563 2553 2543 2534 2526 2001 1985 1970 1954 1940 1926 1913 1718 1700 1680 1662 1643 1626 1610 1548 1526 1503 1482 1461 1442 1423 1433 1408 1383 1360 1336 1314 1293 1350 1322 1296 1269 1244 1219 1197 1286 1257 1228 1200 1173 1146 1121 1236 1205 11’75 1145 1116 1088 1061 1196 I164 1132 1100 1069 1039 1011 1163 1130 1098 1063 1030 999 969 1112 PO76 1040 1004 935 903 969 1075 1037 886 852 923 998 960 1047 1007 926 848 811 886 967 1026 984 817 778 857 941 899 1009 965 791 751 834 921 877 978 743 699 790 885 932 837 911 960 711 663 760 861 810 947 739 792 897 845 687 635 723 778 887 833 658 615 939 934 879 824 654 599 712 768 643 585 929 781 874 819 702 868 750 627 566 810 889 743 616 552 805 681 739 609 542 675 603 535 671 599 529 668 594 521 591 5116 513 511
600 600 700
1.4 5000 2518 1901 1595 1406 1278 1175 1099 1037 986 942 873 820 777 742 713 658 618 588 564 546 530 507 490 478 468 460 449 441 436 432 429 425
1.3 5000 2511 1891 1583 1391 1257 1157 1079 1016 963 919 847 792 747 711 680 621 578 545 519 498 480 453 433 417 405 395 380 368 361 354 350 342 337 334 332
1
1200 1400 1600
917
858
796
730
659
585
505
=
x
= number of upper phase trans-
1.184 1.140 1.095 1.049
8Qo
1p
P
420
328
1.2 5000 2505 1883 1572 1379 1243 1142 1063 998 945 899 826 769 723 685 653 590 545 509 481 458 439 408 384 366 351 338 319 304 293 284 2’97 263 255 249 244 241 238 235 233 231 230
228
1.1
5000 2501 1877 1565 1370 1234 1132 1052 986 932 886 811
753 706 667 634 569 522 485 455 430 409 376 350 329 312 298 275 257 243 231 222 203 190 180 172 166 160 152 147 142 138 136 131 127 124 122 120 119
M 0th PBXP
ratio of partition coefficients, K A and Ker of two solutes, A and B.
+
fers per cycle of z y transfers. = number of lower phase transfers per cycle of z g transfers. = p value, derived from known partition coefficients. = p value, calculated from S.S.D. results.
+
LITERATURE CITED
(1) Alderweireldt, F., Bull. SOC. chirn. Bel . 67, 225 (1958). (2) Afderweireldt, F., J. Chromalog. 5 , 98 (1961). (3) Auer, P. L., Gardner, C. S., Ind. Eng. Chem. 40, 39 (1954). (4) Bush, M. T., Densen, R. M., ANAL. CHEM.20, 121 (1948). (5) Compere, E. L., Ryland A. L., Ind. Eng. Chem. 46,24 (1954). (6) Peppard, D. F., Peppard, &I. A,, I@., 46, 34 (1954). (7) Rigby, F. L., J. Am. Chem. BOC. 74 6118 (1952). (8) dcheibel, E. C., “Technique of Organic Chemistry,” 2nd ed., Vol. 111, 332, Interscience, New York, 1956. (. 9. b tene, S., Arkiv. Kemi Mineral. Ceol. 18A,Nb. 18 (1944). (10) Verzele, M., Bull. SOC. chirn. Belg. 62, 619 (1953). (111 Verzele. M.. Vallerstein Labs. Com’ hum. 18,’62 i8l (1955). (12) Versele, id., Alderweireldt, F., Nature 174, 702 (1954). RECEIVED for review February 10, 1961. Accepted August 24, 1961.
Corrections tion Methods f Vapors
low concentrations which are finally ried out after 37 upper phase and 36 lower phase transfers. The distribuobtained in fundamental C.C.D. The tion was continued with a slightly S.S.D. separation proved entirely sucincreased number of upper phase transcessful. IC ti phase system of benzene fers. After 282 lower phase and 287 and t ~ e t h a n o ~ a m i n(150 e grama)-ethylene glycol (250 ~ r a m s ) - h y d r o c h ~ o r ~ ~upper phase transfers, the correct acid (24 ml., llN)-water (to 1 liter) y/z program was found to be 5/6. bal partition coeficient was This program was run for 2 daya and higher than I. Separation by nights, until the total transfer number f ~ d t i ~ e n C.C.D. t a ~ gave a fl value of was 1220. The results are shown in 2.2 between h ~ ~ and~ cohuuione. ~ n e Figures 7 and 8. From the collected ~ d h u m u l o n e has a higher partition uent 12 grams of pure cohumulone coefficient than h u u l o n e . The starting were isolated. mixture (50 grams) contained 40% coIn a similar manner adhumulone was humulone, 22% humdone, and 38% also successfully isolated from humuadhumulone as determined by partilone, although the fl value is here only tion chroma~graphy (11). The feed 1.5.
calculating the data of Table I.
In this article by 3. E. Lovelock [ANAL.CBEM.33, 162 (1961)], on page 168, Figure 8, the inside diameter of the flame ionization detector is 2.5 cm. On page 169, Figure 9, the inside diameter is 1.0 om. On page 177, reference 96, the volume number should be 187 instead of 185.
~ ~ e ~ ~ ~ o ~ h o t o ~ e t r i ~ ination of Man in Gasolin In this article by E. D. Steinke, B. A. Jones, and Manuel Brandt [ANAL CHEW 33, 101 (1961)], reference to a similarpaper was omitted inadvertently. The paper is “Identification and Quantitative Analysis of Manganese in oUnes” by MI. Pedinelli [Chim. e (Milan)41, 1180 (1959)l.
