Conclusions
Design equations which are similar t o those for Newtonian fluids have been developed for low Reynolds number heat transfer for pseudoplastic and Bingham plastic fluids. The correlation method is based on methods used for correlating rates of viscous dissipation of energy in non-Newtonian fluids. The variation in heat transfer coefficient with impellervessel wall clearance was investigated. The data obtained show a minimum in the heat transfer coefficient with wall clearance and indicate a n optimum clearance to tank diameter ratio to be greater than 0.06. Scale-up relationships for heat transfer to both pseudoplastic and Bingham plastic fluids have been derived for two common design criteria. Acknowledgment
The statistical analysis of the data was facilitated by the provision of computer time by the Computer Center of the University of California, Santa Barbara, Calif. Nomenclature
exponent on Reynolds number, Equation 3 area for heat transfer, ft2 proportionality constant defined by Equation 5 exponent on viscosity ratio number, Equation 3 constant defined by Equation 3 clearance between impeller and wall, ft heat capacity a t constant pressure, Btu/lb OF D = diameter, ft h = heat transfer coefficient, B t u / h r O F f t 2 H = height of liquid in heat transfer vessel, ft H a = height of anchor., ft k = thermal conductivity, Btu/hr OF ft K = flow consistency index, lb/ft seezpn m = mass of fluid, lb n = flow behavior index X = impeller speed, rev/sec P r = Prandtl number, defined by Equation 10 K u = Nusselt number = h D J k R e = Reynolds number, defined by Equation 9 N,,,, = viscosity ratio number, defined by Equation 11 q = rate of heat transfer, Btu/hr a
= = = = C = Cl = C, =
A A, c
S t
T
w
= = = =
ratio of tank diameter to agitator diameter time, h r temperature, O F width of agitator, ft
GREEKLETTERS = = y = ya = 7 = CY
/3
pe p 7 7y
= = = =
constant defined by Equations 19 and 25 constant = H I D , shear rate, sec-l average shear rate, sec-' coefficient of rigidity, lb/sec ft effective viscosity, defined by Equation 4,lb, see ft density, lb/ft3 shear stress, Ib/ft sec2 yield stress, lb/ft see2
SUBSCRIPTS a = agitator b = bulk fluid B = Bingham plastic p = pseudoplastic t = tank w = n-all 1 = full-scale model 2 = prototype literature Cited
Calderbank, P. H., Moo-Young, M.B., Trans. Inst. Chem. Eng., 39. 338 11961). Ferment, G.,-LIS thesis in Chemical Engineering, Sewark College of Engineering, Xewark, Del., 1962. Friend, P. S , LIASc thesis, Universitv of Delaware, Newark. Del., 1959. Heinlein, H. W., 11s thesis in Chemical Engineering, University of California, Santa Barbara, Calif., 1971. Martone, J. -4.,Sandall, 0. C., Ind. Eng. Chem. Process DES. Develop., 10,86 (1971). hletzner, A. B., Otto, R. E., AIChE J . , 3, 3 (1957). Skelland, A. H. P., Dimmick, G. R., Ind. Eng. Chem. Process Des. Develop., 8 , 267 (1969). Uhl, V. W., Chem. Eng. Progr. Symp. Ser., 51, 93 (1954). Uhl. V.W.. T'oznick. H. P.. Chem. Ena. Prom.. 5 6 . 72 11960). Vaughn, R. D., P h b thesis, University 2 fieliware, Newark, Del., 1956. RECEIVED for review Kovember 4, 1971 ACCEPTED April 24, 1972
Development of a Laboratory-Scale Reciprocating Plate Extraction Column Teh C. 10' and Andrew E. Karr Hofmann-La Roche Inc., ,Yutley, S . J . 07110
Performance data on a 3-in.-diam open-type perforated plate reciprocating extraction column first were reported by Karr (1959). I n a recent paper (Karr and Lo, 1971), performance data on a 12-in.-diam reciprocating plate column as well as on a scale-up procedure were presented. The scale-up procedure was based on data obtained in 1-in., 3-in., and 12-in.-diam columns. The data presented agree with the general conclusion T o whom correspondence should be addressed
reached by other investigators (Baird et al., 1971; Elenkov et al., 1966; Gelperin et al., 1965; Issac and DeRitte, 1958; Landau et al., 1964; Prochazka et al., 1971; Wellek et al., 1969), namely, that extraction columns provided with internals having reciprocating motion generally have high volumetric efficiencies. There is a great need for a laboratory extraction column which possesses high extraction efficiency, high capacity, simple construction, and versatility for extraction process Ind. Eng. Chem. Process Der. Develop., Vol. 1 1 , No. 4, 1972
495
_^_-
12"
ENLARGED
VIEW ( 6 )
24"
12" PERFORATED
PLATE
DETAIL ( A )
S/S-1/ 51s-3,'
0 D TUBE
O D TUBE
Figure 1 . Extraction column assembly and details
studies. Kork conducted in our laboratories over a period of many years, as well as bhe results presented herein, has convinced us that the 1-in. reciprocating plate extraction column described in this paper meet,s the aforementioned criteria. The column has been available for laboratory as well as largescale use since 1965 (AIooney Brothers Corp., 1965; Chem. Processing, 1966). Experimental
Description of Column. The reciprocating plate column employed in this work is shown in Figures 1-3. The column consist'ed of a series of open-type perforated plates mounted on a central shaft which was reciprocated by means of a simple drive mechanism at t h e top of the column. The column was made from a section of 1-in. i.d. Pyres pipe. Twenty-fire plates on 1-in. plate spacing were distributed over a height of 24 in. by using 1/4 iii.-o.d. X 0.135 in. i.d. X 18/16 in.-L Teflon spacers. One foot above and one foot below the plates were provided for disengaging space. Oneeighth-in. i.d. inlet tubes of 316 stainless steel were extended approximately 10 in. into the t'op and bottom of the column for the feed streams of light and heavy phases. The plates, as detailed in Figure 1 (A), were punched out of a l/l&. Teflon sheet, and had a free area of approximately 5076. The relatively large openings and high free area in the plates are features of this type of column (Karr, 1959). The diameter of the plates was 1.000 (+O.OOO or -0.010) in. 496 Ind. Eng. Chem. Process Des. Develop., Vol. 1 1 , No. 4, 1972
The reciprocation mechanism was driven by a l/io-hp, singlephase, 115-V de mot'or. The amplitude could be varied between 0 and 2 in. by adjusting the length of a cam arm, although the present series of runs was carried out a t a constant amplitude of in. Figure 3 shows the mechanical assembly of the reciprocation mechanism. The speed of reciprocation could be controlled precisely over a range of 50-600 strokes/ min (cycles/min) by using a B&B Model TR-12AD motor speed controller. The reciprocating speed was measured by the electronic tachometer, Standco Model 460, shown in Figure 2. Operating Procedure. The system used in this work was methyl isobutyl ketone (hl1BK)-acetic acid-water. The distribution d a t a employed were the same as those previously reported (Karr, 1954; Scheibel and Karr, 1950). The solute was first extracted from the aqueous solution by t,he l I I B K phase. I n t h e following run, t h e solute was extracted from the organic phase by t h e aqueous phase. The following are the b o types of runs made in t'he 1-in.diam column: water dispersed-XIBK extractant and water dispersed-water extractant. The solvent ratios employed were mainly such that the operating line was approsimabely parallel to the equilibrium curve, and they are given in Tables I and 11. The concentration of acid in the feed solutions was maintained within limits (12.0-18.7%) to minimize the effect of solute concentration on the results.
Data were obtained on a laboratory-scale, open-type perforated reciprocating plote extraction column.
A minimum height of an equivalent theoretical stage (HETS) of 2.8 in. and valumelric efficiencies of up to
532 hr-' were achieved in a 1 -in. diam calumn employing a MIBK-acetic acid-water system. The HETS values ore lower and the volumetric efficiencies are significantly higher than those achieved with other designs of mechanically aided extractors. The column is simple in construction and it i s versatile for laboratory process studies.
The liquid extraction system used in this work is shown in Figure 4. The feed solutions were maintained a t approximately 22°C. The solutions were mutually saturated in the 10-gal. 316 stainless steel tanks. The aqueous and organic feed streams were introduced into the column by the '/s-hp laboratory centrifugal pumps through calibrated rotameters, and the feed rate was controlled by needle valves. All lines, pumps, valves, and tanks were made of 316 stainless steel, and, by using Teflon gaskets and packings, care was taken t o avoid contamination of the solvents. The column first was filled with the continuous phase, and then the interface was established at the bottom of the column. The flow rate was adjusted, and the desired reciprocating speed was set by the speed controller. The interface was kept in as constant a position as possible by controlling the bottoms draw-off micro-regulating needle valve, and usually was maintained a t about 6 6 in. from the bottom of the column. The column reached a steady state by the time the contents of the column had been replaced three times. Actually more than three times the volume of the column was fed hefore samples of the exit streams were taken for analysis. The acid in the extract and raffinate was analyzed by titration with O.1N standard caustic solution. When the' analyses of two consecutive sets of samples were in close agreement, it was assumed that steady state had been reached. Material balanees were checked and in most cases were 97-10370. Runs
Figure 2. One-in.-diam reciprocating plate extraction column
showing material balance discrepancies greater than 570 were discarded. Results
As mentioned above, all the data were obtained using a 1in, plate spa,cing aud '/*in. amplitude. Previous work (Karr, 1959; Karr and Lo, 1971) indicated that, for the system investigated, these conditions would produce the best column performance. Effect of Reciprocating Speed, Strokes/Min (SPM). The d a t a obtained are given in Tables I and 11, and Figures 5a and b show the plots of H E T S vs. reciprocating speed for two types of runs-Le., water dispersed-MIBK extractant and water dispersed-water extractant, respectively. T h e total throughput investigated for the first type of run was in the range of 572-1435 gal./br/ftz, and, for the second type, 459-1030 gal./hr/ftz. The data show that HETS decreases with increasing SPM up to the flooding point. The miuimum HETS achieved for water dispersedMIBK extractant was 2.8 in., and for water dispersed-water extractant, 4.2 in. A summary of minimum IIETS values achieved for the two types of operation is given in Table 111. Effect of Throughput. The effect of throughput on the
Figure 3. Detailed view of the top of extraction column
Ind. Eng. Chem. Process De,. Develop., Vol. 1 1 , No. 4,
1972 497
Table 1. 1-In. Reciprocating Plate Extraction Column Summary of Data
System: methyl isobutyl ketone-acetic acid-water water dispersed-MIBK extractant Plates spat-
No. of
Run No.
Symbol
plates
ing, in.
Concn of acetic acid, wt
~ ~ ~Agitator l i - Flow rates of feed streams, tude, speed, gal./hr ft2 in. SPM MlBK H20 Total
MlBK in
MlBK out
249.0 249.0 249.0 249.0
0 0 0 0
14.545 14.295 14.32 .,.
1 1 1 1
360 345 320 373
323.0 323.0 323.0 323.0
572.0 572.0 572.0 572.0
H 2 0 in
No. of Plate theeeffiretical ciency, H20 out stages ?' &
%
18.705 5.715 8 . 0 18.75 5.43 7 . 5 18.735 5.80 7 . 1 18.735 . , , . . .
in.
(H/L) Rot-a (H/L) MSCb
1,000 0.985 '/2 0.985 '/z Column flood 1 Az 25 1 '/z 401 456.5 456.5 913.0 0 12.15 17.05 2.91 8 . 8 35.4 2 . 8 1,021 1 '/z 393 446.0 479.0 925.0 0 12.53 17.04 4.01 8 . 1 32.4 3 . 1 0.983 3 25 A2 25 1 '/z 312 446.0 482.0 928.0 0 12.46 17.50 5.58 5.65 22.6 4 . 4 1.025 5 19 A2 25 1 '/z 0 446.0 482.0 928.0 0 8 . 2 9 15.84 8.75 1 . 4 5 . 6 1 7 . 5 0.951 23 A2 32 (1). '/z 322 446.0 482.0 928.0 0 11.67 15.78 4.64 7 . 5 30.0 3 . 3 1.009 2 Az 25 1 '/2 446 456.5 456.5 913.0 0 ... 16.53 ... . . . . . . . . . Column flood 15 A3 25 1 '/z 311 674 761 1435 0 11.335 15.89 5.95 4 . 8 1 9 . 2 5 . 2 1.004 21 A3 25 1 '/z 0 674 761 1435 0 8.875 15.84 8 . 5 0 1 . 6 6 . 4 15.6 1.02 17 A3 25 1 '/z 369 674 761 1435 0 . . . 15.895 . . . . . . . . . . . . Column flood Heavy-to-light phase flow rate from rotameter reading. * Heavy-to-light phase flow from analysis and mutual solubility curve. Top 6 in. of column plate spacing is 1/2 in., middle 8 in. is 1 in., bottom 10 in. is l/z in. 9 11 13 7
A1
Ai A1 Ai
25 25 25 25
'/z
'/z
32.0 30.0 28.4 . . . .
HETS,
3.1 3.3 3.5 . .
(1
Table II. 1-In. Reciprocating Plate Extraction Column Summary of Data
System: methyl isobutyl ketone-acetic acid-water water dispersed-water extractant Plates spat-
No. of
Run
No.
6 8
Symbol
plates
ing, in.
81
25 25
1 1
'/z
25 25 25 25 25
1 1 1 1 1
'/2
01
12 2 4 10 2~
~ ~ ~Agitator l i - Flow rates of feed streams, tude, speed, gol./hr ft2 in. SPM MlBK Hz0 Total
01 02 02
02
8 2
278 280
376.8 181.7 376.8 181.7
241 152 115 0 180
376.8 670.5 670.5 670.5 670.5
'/z
'/z
'/z
'/z '/2
181.7 359.1 359.1 359.1 359.1
Table 111. Summary of Minimum HETS Values Types of runs
Symbol
SPM
Throughput, gph/ft2
Minimum HETS, in.
Water dispersedM I B K extractant Water dispersedM I B K extractant Water dispersedM I B K extractant Water dispersedwater extractant Water dispersedwater extractant
AI
360
572
3.1
Az
401
913
2.8
A3
311
1435
5.2
81
278
458.5
4.2
8 2
152
1029.6
8.1
498
Ind. Eng. Chem. Process Des. Develop., Vol. 1 1 , No.
4, 1972
MIBK
MIBK
in
out
H~O in
% H~O out
No. of Plate theeeffiretical ciency, stages %
HETS, in.
WL)
Rot. (H/L) MSC
458.5 16.785 0.815 0 16.075 6 24.0 4 . 2 1.033 458.5 . . . . . . 3.02 ... . . . . . . . . . Column flood 458.5 11.79 4.67 3.02 14.64 5.84 23.4 4 . 3 1.029 1029.6 16.53 2.65 0 14.74 3 . 1 1 2 . 4 8 . 1 0.996 1029.6 1 6 . 5 3 3.67 0 13.79 2 . 3 9 . 2 1 0 . 9 0.961 6 . 0 1 6 . 7 0.953 1029.6 11.79 6 . 7 3 3.11 11.525 1 . 5 . . . . . . . . . Column 1029.6 16.53 . . . 0.00 ... flood
minimum HETS is shown in Figure 6. I n t h e range of t h e throughput investigated, t h e d a t a indicate t h a t t h e minim u m HETS increases with increasing throughput. It is apparent that, for t h e runs where t h e direction of mass transfer is from the aqueous to the organic phase, t h e HETS values are lower t h a n those in the runs where t h e mass transfer is from organic to t h e aqueous phase a t the same specific throughputs.
~~~~~
Concn of acetic acid, wt
Volumetric Efficiency. Treybal (1959) suggested volumetric efficiency, which has the net units reciprocal hour as a measure of the efficiency of a n extraction column. The volumetric efficiency is the ratio of throughput per unit area per unit time divided by the height of a n equivalent theoretical stage in consistent units. I n Table I V , volumetric efficiencies achieved are presented along with similar data reported in the literature on columns smaller than 2 in. in diam. Volumetric efficiencies up to 532 hr-l were achieved which are significantly higher than those reported in the literature for other designs of mechanically agitated columns. Figure 7 shows the effect of throughput on volumetric efficiency. I n the runs employing water as the dispersed phase, consistently higher volumetric efficiencies were achieved when mass transfer was from the dispersed phase to the continuous phase than when mass transfer was from the continuous phase to the dispersed phase a t the same specific throughput. Discussion
As previously mentioned, the data obtained on the MIBKacetic acid-water system show HETS continuously decreasing with increasing SPM up to the flood point. This character-
Figure 4. Flow diagram of 1 -in. reciprocating plate extraction system
SYMBOL EFFECTIVE NO.OF PLATE AMPLICOLUMN PERFORATED SPACING, TUDE, HEIGHT PLATES INCHES INCHES INCHES WATER DISPERSED Ml0K EXTRACTANT
-
MASS TRANSFER DIRECTION
A
25
WATER DISPERSED
25
-
MASS TRANSFER DlRECllON
25
SUISCRIPT
*
d-c
1
;
WATER EXTRACTANT d-c*
25
TOTAL THROUGHPUT G.P.H./FT'
-
458 572 913 -1030 1435 FLOODPOINT
1
2 3 F
L
0
1
2
3
.
5
4 d*DISPERSED PHASE
..CONIINUOUS
PHASE
I P M ~10.'
Figure 5. Effect of reciprocating speed on HETS, MIBK-acetic acid-water system
istic was also observed in a 3-in. diam column (Karr, 1959), and, based on data on other systems in a 3-in. diameter column, i t can be concluded that most systems studied in a 1-in. diam column would exhibit the same phenomenon; that is, the minimum HETS would be expected to occur near the flood point. Thus, a t a n y selected throughput, operation of the 1-in. diam column a t a reciprocating speed close to that which would result in flooding should result in optimum performance of the column. This characteristic is not necessarily so in other types of small-diameter columns described in the literature. As a matter of fact, most of the data on other types of columns indicate that HETS passes through a minimum as the degree of agitation is increased.
IA
WATER O I I P E I S E D - M I I K
IXTRACIANT
I n evaluating column performance with respect to volumetric efficiency, the column diameter and the extraction system investigated should be taken into consideration. For this reason, only columns having diameters up t o 2 in. and employing the MIBK-acetic acid-water system were compared as shown in Table IV. Volumetric efficiencies obtained in the 1-in. diameter reciprocating plate column used in the present work are significantly higher than those reported for similar data in other extraction columns. Based on preliminary work, a '/*-in. amplitude and a uniform 1-in. plate spacing were found to be optimal for the MIBK-acetic acid-water system. However, frequently it is desirable to provide different plate spacing in different sections of the column to optimize the performance of the
I
boo
I
5oo
A
WATER DlSPlRSEO-MIIK EXTRACTANT WAlER DISPERSED~WA~EREXIPACTANT
b
4 o
o
:
=
o
8 :
THROUGHPUT 0. P. H./FT2
/ 100
0
500
,000
ICQ
THROUGHPUT G . P . H . / F T ~
Figure 6. Effect of throughput on minimum (HETS)
Figure 7. Volumetric efficiency vs. throughput Ind. Eng. Chem. Process Des. Develop., Vol. 11, No. 4, 1972
499
Table IV. Comparison of Volumetric Efficiencies
MIBK-acetic acid-water system
Column diam, in.
Type of column
Controlled cycling sieve plate (Szabo et al., 1964) Reciprocating plate (this work)
2.0
Water
1
Rater Water Water Water Water
304
d-c d+c d-c d+c d-c
572 913 1435 458.5 1029.6
76.4 122.2 191.7 61.3 137.3
hIIBK
d+c
1710
MIBK NIBK
d+c d+c
786 920
h4IBK MIBK MIBK continuous phase.
d+c d+c d+c
149 143 266
1.57 1.57
=
column. For example, in fractional liquid extractionoperations, i t has been found by experience that the plates should be spaced farther apart near the feed section of the column than near the end sections of the column. The basic reason is that, near the center of the column, the concentration of solutes is normally higher and the interfacial tension is normally significantly lower than in the end sections of the column. The latter thus requires a higher intensity of agitation than the center of the column. This phenomenon has been observed in practice in our laboratories for various applications, such as in the purification and separation of various types of organic compounds. Application
Small-diameter reciprocating plate extraction columns have been successfully used for countercurrent and fractional liquid extraction in laboratory and pilot plant process development and scale-up work (Chem. Process., 1966; Karr, 1970; Karr and Lo, 1971; Lo et al., 1971; Penny, 1971; Schweitzer, 1970; Treybal, 1963). X 2-in.-diam reciprocating plate column was used in the pilot plant work leading to the development of tetraethylene glycol (TETRA) as a n efficient solvent in the Udex process (Somekh, 1969, 1971). The extractor has been found to be suitable for processing mixtures with emulsifying tendencies and for liquids containing suspended solids. The reciprocating plate column has been accepted in the commercial application of columns up to 18 in. in diameter (Chem. Process., 1966; Karr and Lo, 1971; Schweitzer, 19iO). Columns of larger diameter are in the design stage. Conclusions
Over a period of several years, various laboratory scale studies were made on a 1-in.-diam reciprocating plate eatraction column previously developed (Karr, 1959). The column has the following features: It is simple in construction and easy to operate and maintain. It offers a great degree of versatility. Reciprocatlng speed, amplitude, and plate spacing are readily changed to provide optimum process performance. 500 Ind.
Max. toto1 throughput Gol./(hr ft2) Vt, ft3/(hr ft*)
2275
Spray (Fleming and Johnson, 1953) 2 . 0 Pulsed spray (Billerbeck e t al., 1956) 1.5 Pulsed packed (Chantry et al., 1955) Pulsed sieve-tray (Chantry et al., 1955) a d = dispersed phase, c
Dispersed phase
Volumetric efficiency,
Directiona of mass transfer
Eng. Chem. Process Des. Develop., Vol. 11, No.
4, 1972
In.
Min. HETS Ft
V(/HETS, hr-'
14.1
1.17
260
3.1 2.8 5.2 4.2 8.1
0.26 0.23 0.43 0.35 0.68
294 532 456 175 202
228
14.4
1.2
191
105 123
11.0 14.5
0.92 1.21
114 102
5.2 4.0 9.2
0.43 0.33 0.77
47 58 46
19.9 19.2 35.6
For the IIIBK-acetic acid-water system, the column was found to have the lowest HETS and the highest volumetric efficiency compared with other small-diameter extraction columns. a given throughput, HETS does not pass through a minimum but, instead, decreases continuously as the speed of reciprocation increases until the flooding point is reached. This characteristic is highly desirable since it provides a straightforward means of selecting the optimum speed of reciprocation. The column has been found to be suitable for processing mixtures with emulsifying tendencies and for liquids containing suspended solids. Acknowledgment
The authors are grateful to Hoffmann-La Roche Inc., for the use of their facilities and for the permission to publish this work. Thanks are given to &irehieFrunzi for the fabrication of t'he column and to Tom Hart'y for assist'ance in performing the experiments. Thanks are also extended to Anna Toto and Cassius Brown for their assistance in the preparation of this manuscript and the drawings. Nomenclature
F
flooding point strokes/min height equivalent to a theoretical stage, in. or ft V T = total volumetric flow rate, ft3/hr, f t 2 D = column diam, in. d = dispersed phase c = continuous phase H = heavy phase L = light phase =
SPllI. HETS
= =
literature Cited
Baird, 11. H. I., LIcGinnis, R. G., Tan, G. C., Paper presented at International Solvent Extraction Conference, The Hague, The Netherlands, April 18-23, 1971. Billerbeck, C. J., Farquhar, J., Reid, R. C., Bresee, J. C., Hoffman, il. S., I n d . Eng. Chem., 48, 182 (1956). Chantry, W.A., von Berg, R . L., Wiegandt, A. F., ibid.,47, 1133 (1955).
Elenkov, D., Boyadzhiev, L., Krustev, I., Izv. Inst. Obshta ,Yeorg. Khqm. Bulg. Akad. IYauk., 4, 181 (1966). Fleming, J. F., Johnqon, H. F., zbid.,49,497 (1953). Gelperin, S . I., Neustroyev, S. A., Khine. Prom., 1, 37 (1965): Brit. Chem. En9. Abstr., 11, 528 (1966). Issac, N.,DeWitte, R . L., AIChE J., 4, 498 (1958). Karr. A. E.. ibid..5 . 446 11959’1. Karr: A. E:, Scheibel, E.‘G., Chem. Eng. Progr. Symp. Ser. S o . IO. 50. 73 (1954). Karr, -4.E., U.S.patent 3,327,760 (1970). Karr, A. E., Lo, T. C., Paper presented at International Solvent Extraction Conference, The Hague, The Netherlands, April 18-23, 1971, J. G. Giegory, B. Evans, and P. C. Wenston, Eds., “Proceedings of the International Solvent Extraction Conference 1971, Vol 1, pp 299-320, Society of Chemical Industry, London, 1971. Landau, J., Prochazka, J., Souhrada, F., h’ekovar, P., Collecf. Czech. P h t m . Commun., 29, 3003 (1964). Lo, T. C., Karr, A. E., Bieber, H. H., Stokes, J. D., Frohlich, G. J., and Kohler, E., Hoffmann-La Roche Inc., Sutley, S . J . , unpublished reports, 1938-72. Nooney Brothers Corp., (Little Falls, N.J.,) Karr Reciprocating Plate Extraction Column, Bulletins KC-1 and KC-2 (1965). Penny, W. I
