e
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1953
two Tennessee limestones a t 700” C. in steam proved superior to corresponding limes from industrial kilns. The gaseous effluent from the prescribed calcination in steam at 700 O C. was readily freed of solid matter, and a t the dew point of steam the effluent gas becomes high-purity carbon dioxide that is available for liquefication and for conversion into dry ice. The foregoing findings ($7) represent the initial record of jointly implemented catalysis and mechanics of fluidization to effect a markedly expedited calcination of limestone fines a t a substantially lowered temperature. ACKNOWLEDGMENT ”x
w
The laboratory findings and their implementation into large scale operations on both dolomite and limestone were the immediate responsibility of the late junior author. Material assistance in the limestone calcinations was rendered by Jack Thompson, now of Oak Ridge, Tenn. REFERENCES (1) Assoc. Offic. Agr. Chemists, J . Assoc. Ofic. Agr. Chemists, 21, 58 (1938). (2) Azbe, V. J., Rock Products, 51, 86-9 (September 1948). (3) Azbe, V. J., “Theory and Practice of Lime Manufacture,” pp. 36-9 (as of 1926). (4) Bailey, Rock Products, 25, 19 (Oct. 7 , 1922). (5) Bole, G. A., and Shaw, J. B., J . Am. Ceram. SOC., 5,817 (1922). (6) Clarke, F. W., U. S.Geol. Survey, Bull., 330 (1908). (7) Ibid., 616 (1916). ( 8 ) lbid., 770, 566 (1924). (9) Cunningham. W. A.. IND. ENG.CHEM..43. 635 (1951). (10j Frear, Wm., Pa. State College Expt. Sta., Annual Report, Part 2, 48 (1899). (11) Garner, W. W., McMurtrey, J. E., Bacon, C. W., and Moss, E. G., J . Agr. Research, 23, 27-40 (1923). (12) Hall, C. C.. and Jolley, L. J., Petroleum, 13, 217-23 (September 1950). (13) Herzfeld, Festschrift zur Eroffnung des Instituts ftir Zukerindustrie, p. 469, cited by Knibbs (16, p. 102). (14) Kallauner, O., Chem.-Ztg., 37, 1317 (1913). (15) Kite, R. P., and Roberts, E. J., Eng. Mining J., 148, 146-50 (November 1947); Chem. Eng., 54, 112-15 (December 1947). (16) Knibbs, N. B. S.,“Lime and Magnesia,” London, Ernest Benn, 1924. (17) Lathe, F. E., Proceedings of Engineering Institute of Canada, Montreal. Quebec. Feb. 8-9. 1934. (18) Leather, J. W., and Sen, J. N., Mem. Dept. Agr. India, Chem. Ser., 3, No. 8, 204-34 (1914). (19) Lenhart, W. B., and Rockwood, N. C., Rock Products, 11, 3-116 (January 1948). (20) Lime Conference Proceedings, Knoxville, Tenn. 1
,
1555
Lipman, J. G., Blair, A. W., McLean, H. C., and Prince, A. L., S o i l S ~ i .15, , 307-28 (1923). MacIntire, W. H., J . Assoc. Ofic. Agr. Chemists, 16, 589-98 (1933).
MacIntire, W. H., Soil Sci., 7, 325-453 (1919). MacIntire, W. H. (to University of Tennessee), U. S. Patent 1,953,419 (1934).
MacIntire, W. H. (to American Zinc, Lead & Smelting Co.), Ibid., 2,118,353 (1938). Ibid., 2,155,139 (1939). Ibid.., -,-2.212.446 . - ~(1940). Ibid., 2,403,940 (195lj. MacIntire, W. H., Hardin, L. J., and Oldham, F. D., IND. ENG.CHEM.,28, 711-17 (1936). Ibid., 30, 651-9 (1938). MacIntire, W. H., and Shaw, W. M., Ibid., 24, 1401-9 (1932). MacIntire, W. H., and Shaw, W. PI., J . Am. SOC.Agron., 22, 14-27 (1930).
Ibid., pp. 272-6. Ibid., 26, 656-61 (1934). MacIntire, W. H., and Shaw, W. M., Soil Sci., 20, 403-12 (1925).
MacIntire, W. H., Shaw, W. M., Hardin, L. J., and Winterberg, S.H., Ibid., 65, 27-34 (1948). MacIntire, W. H., and Shuey, G. A., IND.ENQ. CHEM.,24, 933-41 (1932).
MacIntire, W. H., Winterberg, S.H., Sterges, A. J., and Clements, L. B.. Soil Sci.. 67, 289-97 (1949). Mehring, A. L., Research Administration, U. S. Dept. Agr.,. letter, Dec. 4, 1951. Mitchell, A. E., J . Chem. SOC.Trans., 123, 1055 (1923). Murray, J. A., Fischer, H. C., and Shade, R. W., Proceedings. p. 32, Annual Convention of National Lime Assoc., hIay 11-13, 1950.
Myatt, D. O., Chem. Eng. News, 29, 686 (1951). Ostwald, W., Physik. Z., 3, 313 (1902). Rex, C. R., U. S.Patent, 2,193,842 (1940). Scherer, Robert, “Der Magnesit,” Vienna, Hartleben, 1908. Schwab, G.-M., Taylor, J. S.,and Spence, R., “Catalysis, from the Standpoint of Chemical Kinetics,” p. 16, New York, D. Van Nostrand Co., 1937. Shaw, J. B., and Bole, G. A., J . Am. Ceram. SOC.,5 , 3 1 1 (1922). Shaw, W. M., J . Assoc. Ofic. Agr. Chemists, 24, 244-9 (1941). Shaw, W. M., MacIntire, W. H., and Hill, J. J., Univ. Tenn. Agr. Expt. Sta., Bull. 212 (July 1949). Shaw, W. M., MacIntire, W. H., and Underwood, J. E., IND. ENG.CHEM.,20,312 (1928). Sweet, F., Comm. Fertilizer, 76, 14-21, 42-3 (April 1948). Van Tuyl, F. M., Iowa Geol. Survey, 25, 251-422 (1914). Washburn, D. E., A.S.T.M. Symposium on Lime, Columbus Regional Meeting, March 1939. Whitaker, C. W., Rader, L. F., Jr., and Zahn, K. V., Am. Fertilizer, 91, 5-8, 24 (Dec. 9, 1939). RECEIVED for review September 18, 1952. ACCEPTED March 18, 1953. Presented before the Division of Fertilizer Chemistry at the 122nd Meeting of the AMERICAN CHEMICAL SOCIETY, Atlantic City, N. J.
Some Reactions of Polychlorotri-
fluoroethylene J
MATTHEW T. GLADSTONE1 General Electric Research Laboratory, Schenectady, N . Y .
P
OLYCHLOROTRIFLUOROETHYLENE [Poly F-1113, Kel F (M. W. Kellogg Co.), Fluorothene (Carbide & Car-
bon Chemicals Corp.)] is reported to be thermally stable and chemically inert (4,8,9). Chemical tests on the polymer have generally been run below 100” C., and Frey et a2. ( 2 ) report that under these conditions only chlorine caused a color change in the test sample. Thermally, Watson et al. ( I f ) have shown that poly1
Present address, Behr-Manning Corp., Troy, N. Y.
monochlorotrifluoroethylene does not show any significant decomposition as evidenced by loss of weight or evolution of gas a t 250” C. or below when heated for 3 hours a t temperature in a stream of moist air. However, as this polymer is considered for higher temperature use (4), the effect of various chemicals a t elevated temperatpres is of interest. Therefore the reactions of some organic substances t h a t may be used as dispersion or solvent media and metals t h a t may be used as substrate for films have been studied.
* 1556
Vol. 45, No. 1
INDUSTRIAL AND ENGINEERING CHEMISTRY PROCEDURE
For the reaction of polychlorotrifluoroethylene with or in the presence of organic liquids, the polymer was placed in a 300-ml. three-necked round-bottomed flask fitted with a nitrogen inlet tube, thermometer, and reflux condenser. The reagents were then added, dry nitrogen was passed through for 10 minutes, and the mixture was heated to the desired temperature by means of a Glas-Col heating mantle. The nitrogen was continued for the duration of the experiment and carried through the reflux condenser into a measured amount of standard silver nitrate solution. The amount of chloride was determined by the Volhard method. The total free chloride was measured by extracting the organic layer with water five times and analyzing the extracts as before. The same method was used with amines a s with the reagent, except t h a t the nitrogen was eliminated. I n the direct reaction of metals with polychlorotrifluoroethylene, a fine metal powder was ground in a mortar with the polymer until a uniform appearance was obtained. The mixture was sealed in a tube either with air or evacuated, and placed in an oven at the desired temperature. Upon completion, the tube was removed, and opened, the metal was dissolved by means of concentrated nitric acid, and the solution was filtered and analyzed gravimetrically for chloride. I n some instances the change in viscosity of a dilute solution (,5) was used to find the degree of degradation. MATERIALS
The polychlorotrifluoroethylene was obtained from the AI. W. Kellogg Co. and micropulverized to obtain a fine powder. Polymers of NST 240 ( 7 ) and NST 300 ( 7 ) were used. The organic substances were purified by distillation or recrystallization and the metal powders were freshly reduced in a n atmosphere of hydrogen, The metal halides and oxides were reagent grade chemicals. DISCUSSION AND RESULTS
from the polymer. The effect of time a t a given temperature is shown in Table 11. REACTION WITH OTHER Conwoums. As hydrocarbons gave hydrogen chloride, other compounds were also tried.
TABLE111.
RE.4CTION
O F POLYCHLOROTRIFLUOROETHYLENE WITH OTHERCOMPOUXDS
(1.16 grams of Poly F-1113 S S T 240, 50 ml. of Compound Time, Min. Temp., C. Ethylene glycol 40 189 40 223 Pinacol 180 164 40 225 Propylene glycol 40 225 HexachloroetlianeQ 40 225 Fluorolubeb 40 225 Dichlorobenaotrifluoride C 320 170 Alcoholic KOH 1440 80 Steam and air 120 250
TABLEIv.
RE.4CTIoN
WITH
compound) c1, wig. 0 0.75 0 2.93 0.57 Very small amount Very small amount 4.1 Very small amount
hIETALS IN ORQANIC
LIQUIDS
(2.33 grams of Poly F-1113 KST 300, 0.157 mole of metal, 50 ml. of isoamylnaphthalene. 225' C., 30 minutes) Metal c1, M g . Powder 156 cu A1 44 Ni 17 Foil A1 18.9 Ni 25.2 Pb-Sn (95-5) 6.5 Blank 2.3
These results indicate that, as before, a temperature in excess
of 200' C. is needed, t o cause any reaction in a relatively short
time. The three different glycols were tried to see whether the amount or solutions of polytrichlorotrifluoroethylene contain high boiling of chloride obtained was influenced by whether the hydrogens organic liquids, the effect of high boiling hydrocarbons was inavailable were primary, secondary, or tertiary. The above revestigated. Preliminary work showed that hydrogen chloride sults indicate t h a t primary hydrogens react to a greater extent. was present after heating. That the gas was hydrogen chloride REACTION WITH METALS IS ORGaNIC LIQUIDS. As the above rather than chlorine was established by the acidity, lack of color organic compounds reacted with polychlorotrifluoroethylene t o of the vapor, precipitation of silver chloride, and its nonreaction form hydrogen chloride a t elevated temperatures, the effect of with acidified starch-iodide solution. Table I gives the results metals in the presence of a hydrocarbon was studied because obtained. metals will be the substrate in many coating operations using dispersions or solutions. The reactions were run as described previously, except that when powders were used, the metal and polymer were ground in a mortar until uniform. Table IV gives the TABLE I. REACTION OF POLYCHLOROTRIFLUOROETHYLESE WITH HYDROCARBONS results. (1.16 grams of Poly F-1113 NST 240, 50 ml. of hydrocarbon) The higher value for the nickel foil is possibly a result of the Compound Time, Min. Temp., a C. C1, hIg. unclean surface of the nickel foil used. Cleaner foil would be Tsoamylnaphthalene 10 260 9 32 expected t o fall in line. As experience (based on specific viscosity 40 214 1 75 measurements) has shown marked degradation with removal of 40 225 2 3 10 253 2 6 1-Chloronaphthalene chloride, these results show that the polymer will be degraded t o a 20 235 6 5 I-Methylnaphthalene 2-Methylnaphthalene 20 235 2 5 greater extent in the presence of metals than in the presence of 0 82 1-Fluoronaphthalene 40 212 hydrocarbons alone. It appears that the lead alloy would have the least effect of the metals tried. The difference between the TABLE 11. EFFECT OF TInm powder and the foil is probably a result of the difference in surface (1.16 grams of Poly F-1113 S S T 240, 50 ml. of isoamylnaphthalene. area. Temperatuie 227' C.) REACTION WITH COPPEROXIDES. Because copper has a Time, Min. c1, Mg. greater effect than the other metals, the question arose as to 40 2.0 80 5.3 whether the free copper or the thin coating of oxide is responsible 120 6.7 160 14.8 for this effect. Therefore both cupric and cuprous oxides were 200 16.1 run (Table V). The amount of chloride obtained is much less than with the metal, which, therefore, appears to be the active entity. REACTION WITH METAL HALIDES.Hydrocarbons yield hydroThese results show that a t temperatures in excess of 200' C. gen chloride and, in the presence of metals, the degradation is appreciable amounts of chloride are formed, which must come
REACTION WITH HYDROCARBOSS. Because organic dispersions
July 1953
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY TABLE V. REACTION WITH COPPEROXIDES
1.16 grams of Poly F-1113 NST 300, 60 ml. of isoamylnaphthalene, copper oxide. 225' C., 30 minutes) Chloride, Mg. Oxide Added, Grams Carried over Extracted CuO blank 13.1 ... 0.8 +:4 CUO 13.1 ... 3.2 CuzO blank 23.6 ... 11.1 cuzo 23.6
*9
accelerated. From this the question arises as to whether the metal reacts as such or with the hydrogen chloride formed t o yield qmetal halide which is the active agent. Therefore several metal halides were reacted with the polymer, giving the results shown in Table VI.
TABLE VI. REACTION WITH METALHALIDES (1.16 grams of Poly F-1113 NST 300, 50 ml. of isoamylnaphthalene, metal halide. 225' C., 30 minutes)
a
Chloride Found, Mg. Halide5 Mg. Carried over Extracted 31,7 2.16 29.4 AlCla 3.8 13 5 29.6 AlCla 7.6 16.3 76.9 NiCIt.6HzO ... >53 34.8 FeCls.6HzO 67 Present 35.8 FeCls 28.5 5.7 45.1 CUClZ 23.6 9.2 65 CunClz 13.8 Colloidal 73.3 SnClz.2HzO Blank was aluminum chloride plus solvent.
Excess, Mg. 10.5
....
0.9 >39.1 >43.6 10.3 9.4
....
From these results, it appears that ferric chloride will cause the most extensive degradation of the polymer. Aluminum chloride and copper chloride, although not so reactive as ferric chloride, will still cause appreciable. degradation. In the absence of any REACTIONWITH METALPOWDERS. organic liquids, aluminum and nickel powders ground with the polymer, placed in a tube, and sealed with vacuum or air had little if any effect on the polymer. Copper, on the other hand, was shown in Table IV to have an effect greater than the other metals. Under conditions similar to those used with aluminum and nickel, copper had a much greater effect, as shown in Table VII.
TABLE VII. REACTION WITH METALPOWDERS (2.33 grams of.Poly F-1113 NST 240, 0.32 mole of copper powder, pelletized and run a t temperature for 18 hours) Chloride, Mg. Conditions 2100 c. 2200 c. 250' C. 29.8 140 50.0
Q
... ...
113.0 Enough water used so that pressure is same as in tube with air.
~~
From these data it can be concluded that copper has only a slight effect in vacuum or nitrogen, but this effect is greatly enhanced by oxygen. At higher temperatures, the water probably reacts by direct substitution. REACTION WITH AMINES. Frey and coworkers ( 9 ) found that up to 100' C. only chlorine caused a color change in test samples. However, in this laboratory, H. T. Hall found that polychlorotrifluoroethylene on standing for several days in %-butylamine darkened and the amine also darkened. Amines were therefore tested as described previously, except that the nitrogen was eliminated, as it was felt that the amine would react with any hydrogen chloride formed. The reaction was run using high boiling amines, as higher temperatures were desired to reduce the time involved, The results are given in Table VIII.
1557
Primary amines seem to be more reactive than secondary or tertiary. The reaction is undoubtedly due t o t h e free pair of electrons on the nitrogen, as 2-ethylhexylamine hydrochloride had no effect on the polymer. The mechanism by which hydrogen chloride is formed is in doubt. However, a most likely hypothesis is that a FriedelCrafts type of reaction is occurring. It is known that this type of reaction can occur in the absence of catalyst a t elevated temperatures (IO). As would be expected, more reaction occurs in the presence of metal halides or substances which can form these, further indicating a Friedel-Crafts reaction. As discussed by Egloff et al. ( 1 ) a variety of products can be produced in the reaction of higher alkylated benzenes with aluminum chloride. If it is postulated that other metal halides can act like aluminum chloride, the product of the Friedel-Crafts reaction between an aromatic compound and the polychlorotrifluoroethylene may, under the conditions used, split off the side chain as an olefin or by scission and reaction form polysubstituted aromatics. These products, such as nuclear substituted aromatics or olefins, all have weak links in the polymer chain which can be broken a t the elevated temperatures used. This could explain the degradation of the polymer under the conditions used. Under these conditions fluoride could also be lost, and qualitative tests for fluoride ion, using a saturated calcium chloride solution to trap the vapors, were positive.
TABLE VIII. REACTION WITH AMINES (0.02 mole of Poly F-1113, based on monomer, 0.04 mole of amine, 100 ml. of Solvesso 150) Amine Time, Hours Temp., C. C1, Mg. 2-Eth lhexyl 6 185 188.2 Tri-n-Xexvl
In the presence of metals or metal halides two other possible reactions may contribute to the degradation of the polymer. First, metal chlorides may cause the replacement of fluorine b y chlorine leading to adjacent chlorines which would constitute a weak spot in the chain, especially in the presence of metals. This reaction is known t o occur with aluminum chloride and chlorofluoromethanes and ethanes (3). Secondly, Miller (6) has shown in the reaction of 1,1,2-trichlorotrifluoroethane with aluminum chloride that in addition t o the replacement of the 1 fluorine by chlorine, rearrangement to l,l,l-trichlorotrifluoroethanetakes place in 50% yield. If such a rearrangement occurs in the polymer, adjacent chlorines are formed, which can constitute a weak link.
F F F F
-b-A-A-b . 1 A1 1 bl
--f
F F F F
1 1 1 1 -c-c-c-c
1 A1 A1 k
The reaction with amines discussed previously is undoubtedly more complicated ,than a straight alkylation of the amine by the polyhalide. This, however, probably does occur, since a free pair of electrons is needed. A weak link in the chain would then be formed and degradation occur by scission at the carbonnitrogen bond. A small amount of water will accelerate the reaction, As little as 0.1 ml. of water in 100 ml. of Solvesso 150 (Esso Standard Oil Co.) increased the amount of chloride obtained by a factor of 3. LITERATURE CITED
(1) Egloff, G.. Wilson, E., Hullo, G., and Van Arsdell, D. M., Chem. Revs., 20,345 (1937). (2) Frey, S. E.,Gibson, J. D., and Lafferty, R. H.,IND.ENG. CHEM.,42,2314 (1950). (3) Henne, A. L.. and Leicester. H. M., J. Am. Chem. SOC..60. 864 (1938).
INDUSTRIAL AND ENGINEERING CHEMISTRY
1558
(4) Javitz, A. E., Elec. M f g . , 45 (August and September 1950). (5) Kaufman, H. S., and Aluthana, ill. S., J . Polgmer Sci., 6, No. 2, 251 (1951). (6) LIiller, W. T., Jr., Fager, E. W., and Griswold, P. H., J . Am. Chem. Soc., 72,705 (1950). (7) Miller, W. T., “Use of Perfluoro- and Chloroperfluoroolefinsin the Synthesis of Fluorocarbon Materials,” Columbia Gniversity, S.A.N. Laboratories, Atomic Energy Commission, MDDC-1177(1946). (8) Plax Corp., “Polymerized Chlorotrifluoroethylene,” Atomic Energy Commission, MDDC-818(hlarch 27, 1947). (9) Reysen, W. H., and Vanstrum, P. R., “Properties of Fluoro-
Vol. 45, No. 7
thene,” Carbide & Carbon Chemicals Corp., Atomic Energy Commission, AECD-2032 (Sept. 22, 1948). (10) Thomas, C. A., “Anhydrous Aluminum Chloride in Organic Chemistry,” ACS Monograph 87, p. 68, New York, Reinhold Publishing Corp. 1941. (11) Watson, H. A , , Stark, N. J., Sieffert, L. E., and Berger, L. B., U. 8.Bur. Mines, R e p t . Invest. 4756 (December 1950). R E C E I V E D for review November 20, 1952. ACCEPTEDApril 8, 1953, Presented before the Division of Polymer Chemistry, Symposium on Chlorotrifluoroethylene, joint with Division of Industrial and Engineering Chemistry, a t the 122nd Meeting of the .4UERXCAN CHEXICAL SOCIETY, Atlantic City, N. J.
Dimethvlaniline as an Aid in Acetic Acid-Water Separation LEO GARWIN‘ AND PHILIP 0. HADDAD2 Oklahoma A . & M . College, Stillwater, Okla.
S
EPARATIOS of acetic acid and water is most frequently
carried out hy distillation. Difficulty is experienced, holvever, in the n-ater-rich region because of a low relative volatility. Many attempts have been made t o effect the separation more conveniently, using other types of separation processes, and some of these are practiced commercially. Examples are (11 ) azeotropic distillation with butyl acetate (Othmer process), liquid-liquid extraction, and extractive distillation with a wood oil (Suida process). K o r k has been carried out on the addition of an inorganic salt, calcium chloride, t o reverse the relative volatility of acetic acid and water ( 3 ) . The effect of high pressure on the acetic acid-water vapor-liquid equilibrium has recently received attention ( I O ) . The study reported in this paper was undertaken to investigate the addition t o acetic acid and water of a third component, intended t o improve the normal distillation by exerting a highsolvent action on the acetic acid, thus causing it to be retained in the bottoms stream, and by azeotroping with the water, causing it to come off overhead more readilk, h water-insoluble organic compound having basic properties seemed to be a logical choice, for it would be expected to form a loose complex with the acetic acid, and it would also form a heterogeneous azeotrope (minimum boiling) with water. Most nitrogen compounds were rejected because they form maximum boiling azeotropes Tvith acetic acid (7); this had to be avoided. Aniline has been reported to be satisfactory in this regard (8). Preliminary experiments showed, however, that it could not be used because of its reaction with acetic acid to form acetanilide. Dimethylaniline has been reported (8) as not forming an azeotrope u i t h acetic acid. It would be expected not to react with acetic acid because of the replacement of the t a o active hydrogens on the nitrogen nith methyl groups, and it was therefore selected for study. This report deals with the vapor-liquid equilibrium a t 1 atmosphere of the binary systems acetic acid-water, acetic acid-dimethylaniline, and the ternary system acetic acid-Tvater-dimethylaniline. Because dimethylaniline and water are mutually immiscible, the vapor-liquid equilibrium for this binary system can be readily calculated. The materials used and the analytical procedure employed have been described ( 2 ) . When a sample for analysis consisted of two liquid phases, the sample was brought to 25.0’ C., the conjugate layers were separated and weighed, the composition of each phase ’ Present address, Kerr-McGee Oil Industries, Inc., Oklahoma City, Okla.
* Present
address, Dow Chemical Co., Freeport, Tex.
1%as determined by acetic acid titration and reference t o the ternary system solubility envelope (Z),and the composite composition of the mixture obtained by the lever arm principle, using a triangular plot.
EQUIPMENT AhD PROCEDURE
For all binary system runs and those ternary system runs in which both distillate and residue nere single phase, an Othmer still ( 8 ) was employed. Pressure was, maintained constant a t 760 k 1 mm. of mercury by mcans of a Greiner Cartesian manostat (4). 911 thermometers were checked in place by means of runs with distilled water and with pure dimethylaniline; temperatures were estimated to 0.1” C. Approximately 45 minutes were allowed for equilibrium. The distillate rate was 60 to 66 drops per minute. .4n extended run showed this amount of operating time under these conditions to be ample. Changes in the still pot composition from run to run were made by withdrawing part of the charge and replaring it with one of the pure components. A still described by Hands and Korman (6) vias used for those runs of the three-component system in nhich two phases appeared. The still v a s used also for a fe!\- single-phase runs. In its operation, the distillate, during equilibration, is returned directly to the still pot: there is no distillate holdup. The still is run until constant temperature is reached, and then a small amount of distillate (relative to the amount of residue) is withdrawn as a sample. It was found that 20 minutes running time was sufficient to reach a constant temperature; twice as much time was allowed for each run, however. The distillate sample volume was restricted to 1% or less of the residue volume. After the removal of the distillate sample, the still was allowed to continue to operate until a new temperature equilibrium was established. The changes in residue composition and temperature occasioned by the removal of the distillate sample were small, and
TABLE
I. COl\IPARrSOiX O F VAPOR-LIQUID EQUILIBRIUM STILLS (1 Atmosphere) -4cetic Acid-Water __ _ _
Hands and Korman still Othmer still
Water, Wt,. % Liquid Vapor 46 3 34 2 46 8 34 2
’
Acetic Acid-Dimethvlaniline _Aoet,ic Acid, Wt. % ’ Liquid Vapor 49 6 89 6 49 6 89 6 ~
