Materials Adsorbed at Crude Petroleum-Water Interfaces ISOLATION AND ANALYSIS OF NORMAL PARAFFINS OF HIGH MOLECULAR WEIGHT MILTON 0. DENEKAS', FRANZ T. CARLSON, JOHN W. MOORE, AND CHARLES G. DODD Petroleum Experiment Station, Bureau of Mines, Bartlesville, Okla.
~
a
Film-forming and surface-active constituents naturally present in crude petroleum apparently are responsible for many problems encountered in the production and refining of petroleum. The water-spray extraction method of Bartell and Niederhauser has been employed to isolate such substances from a sample of crude petroleum from the Wilcox formation in the Oklahoma City field by adsorption at an extended oil-water interface. One fraction, isolated from the extract in a yield of about 1 gram per 7.5 liters of oil, has been shown by chemical and physical analysis to consist of normal paraffins con-
taining up to about 70 or 80 carbon atoms. Other fractions, which were obtained in much smaller yields, appeared to contain surface-active material. An unexpected result of the work is the possibility of obtaining normal paraffins of very high molecular weight by extraction from crude petroleum more readily than by chemical synthesis. Wax-containing films deposited on rock surfaces are considered to affect core analysis procedures and laboratory flooding tests significantly, as well as the recovery of petroleum from depleted reservoirs by air and possibly water drive.
T
more rbon atoms in the molecule ( 4 , 7 , 9). Possibly of greater interest is the mechanism by which a nonpolar, n-paraffin hydrocarbon can be accumulated a t an oil-water interface. Furthermore, the possibility of paraffin hydrocarbons forming part of the coating on rock material in oil reservoirs may aid the petroleum engineer in dealing with production problems.
HE chemical nature of the thin, membranous, coherent films which enclose water droplets in crude oil-water emulsions ( 1 , 6, 6, 8, 14) remains largely unknown, despite the technical importance of such emulsions. Films a t oil-water, solid-water, and solid-oil interfaces may appreciably affect the flow of oil and water through minute rock pores in petroleum reservoirs. Exploratory work on the general problem of film-forming substances has been undertaken at this laboratory in an effort t o assess the importance of such materials in petroleum production. The work described herein is concerned solely with a sample of crude petroleum from the Oklahoma City which was produced from the Wilcox formation. This oil (herein referred to as OCW) has been described by Katz as imparting a hydrophobic surface to sand grains allowed t o soak in samples of the oil ( 1 1 ) . The ocw oil w&8 selected for the presentwork to study how it might change the character of the rock surface from the supposedly normal hydrophilic (preferentially water-wet) state t o the observed hydrophobic (preferentially oil-wet) state. Film-forming substances could be separated from the OCW oil by the method of Bartell and Niederhauser (3). This procedure removed the desired materials from the bulk of the oil phase by adsorption a t an extended oilwater interface. A major portion of the material separated has been identified as a mixture of n-paraffins of unusually high molecular weight. The unexpected isolation of n-paraffin hydrocarbons is of interest because there is a paucity of published work concerning the synthesis FILM-COVERED or isolation of straight-chain DROPLETS hydrocarbons having 50 or Present address, Department of Chemistry, University of Tulsa,
ISOLATION OF FILM-FORMING CONSTITUENTS
A 2-gallon sample of oil was taken on April 3, 1949, from the well head of Phillips Petroleum CO.No. 1 Henderson well, Set. 10, T. 11 N., R. 3 W., Oklahoma City field, Oklahoma County, Okla,, producing from the Wllcox sand. The sample was transported to Bartlesville in & tinned container and stored a t 350 to 38" F. until used. At the time the sample was taken, the well was flowing as the result of an applied vacuum. The oil was found t o have a specific gravity of 0.8349 m/mOF. (38.3"A.P.1.) and a viscosity of 5.42 centipoises (48.8 Saybolt seconds a t 7 7 O F.), Preliminary qualitative observations of drops of the OCW oil suspended in water indicated t h a t the sample at hand formed coherent films a t oil-water interfaces in a manner similar the samples observed by Bartell and Niederhauser and suggested the. application of their adsofption method to concentrate the desired material ( 3 ) . A diagram of the apparhtus, which is similar to that of Bartell and Niederhauser, is presented in Figure 1, together with an enlarged diagram of the boundary between oil and aqueous phases in the column. The general extraction apparatus and lower parts of the columns are shown in Figure 2 and 3.
1
Tulsa, Okla.
Figure 1. Diagram of Extraction Apparatus
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As shown in Figure 1, the apparatus consisted of a tortuous glass column (about 15 mm. in inside diameter) with
1166
Figure 2.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
General V i e w of Extraction Apparatus
a reservoir 46 mm. in outside diameter at the top, and a btopcock, separable 500-ml. collecting bulb, and drain-tube connection at the bottom of each column. One third of the column was filled uith water, and crude oil was added until the oil-water boundary in the column had dropped to a point a few inches above the upper stopcock. ilpproximately 500 ml. of oil were charged for each run. The water phase used by Bartell and Niederhauser and by the writers was a 0.001 M solution of aluminum chloride which had a pH of 4.25 to 4.3. The trivalent aluminum ions aided in keeping the inner walls of the glass extraction columns wet by water, thus Dermittine the efficient gravitational PeDaration of oil and Isate;. (No tr&e of aluminuk has been fouid in the extracts.) The solution was sprayed from a fine capillary (about 0.1 mm. in inside diameter) into the oil a t the top of each column under a pressure of 5 to 10 pounds per square inch. The spray formed an extended oil-water interface of fine water droplets which fell throqgh the tortuous, oil-filled column. Numerous indentations in the columns served to provide more intimate contact between oil and water phases and to break up any large drops or "sacs" of watei ( 3 ) . Material was adsorbed a t the interface of each tiny droplet as it moved downward through the oil. Numerous film-covered droplets accumulated in the lower portions of the columns to form cellular, honeycombed masses which partly collapsed and coalesced, releasing water which drained off from the bottom of each column while entrained oil drained upward. -4 period of 3 to 5 days was adequate for removing all the adsorbable material present in a 500-ml. sample of OCW oil. The extracted substance \vas fractionated as indicated in Table I.
To confirm the negative osygen result, tests were run for aldehyde, ketone, ester, acid, ether, and alcohol functional groups. These were also negative. Teqts for olefinic and aromatic unsaturation were negative. No chain branching was detected when the powder was heated in a sealed tube with dilute nitric acid ( 2 0 ) or when it was treated with chlorosulfonic acid (18). A sample for carbon-hydrogen ultimate analysis recrystallized from petroleum ether after decolorizing with charcoal was obtained as a grayish-white, waxlike solid. Analyses of duplicate portions of this sample are reported as samples la and 11, in Table 11. A vacuum fractional distillation of the brown powder a t 1-mm. pressure yielded portions of white, waxlike solids for which the boiling and melting points are given in Table 111. A black residue was insoluble in butyl acetate and chloroform. Decomposition apparently had occurred. A4fraction of material distilled between 290" and 310" (1 nini.) was used without recrystallization as analytical sample 2. Bartell and Niederhauser (3) found that the material they isolated from a California crude oil was adsorbed on charcoal. Because adsorption may have occurred with the carbon-hydrogen sample I, and because decomposition of material was possible upon distillation in the case of sample 2, an additional sample of the brown powder (fraction E), just as isolated by precipitation from acetone, was submitted for analysis to determine any possible loss of some important component from the original miuture. This last sample is designated as sample 3 in Table 11. The ash was nonalkaline and found to be largely iron. Apparently no organic material was lost or destroyed in the isolation procedure, and the evidence indicates that the material is a saturated hydrocarbon. The precision of carbon-hydrogen microanalyses is such that the observed variation of the hydrogen-carbon ratios in Table I1 from 1.965 to 2.023 is probably not significant (16) with respect to the assignment of hydrocarbon species or molecular weights. A portion of the material distilled between 290" and 310" (1 mm.) was used as a sample for infrared analysis. About 0.1 giam of the sample was melted on an optically polished rock-salt plate of suitable size to be substituted for the sample cell in a PerkinElmer infrared recording spectrophotometer. The observrd infrared spectrum confirmed the absence of functional groups, including aromatic and olefinic unsaturation.
TABLE I. ISOLATIOK AND FRACTIONATION PROCEDURE OCW crude petroleum (7.5 liters)
J.
Extract with water spray
Extractive (coalesced foam) Treat with CClr
CClr - insoluble ( B ) (tan, flocculent mass) CC14 solution ( A ) Evaporate CClr, redis-ITreat with acetone solve in toluene 'Acetone solution (D) 'Acetone - insoluble (possibly colloidal) ( E ) (brown, m x y second extraction with mater spray; extrac-1 I powder)
1 ~
AY4LYSIS OF FRACTION E
The powder was found to be insoluble a t room temperature in ether, benzene, toluene, pyridine, diethylamine, chloroform, ethylene dichloride, n-butyl bromide, mesityl oxide, ethylene glycol monoethyl ether, 5% hydrochloric acid, 5 % and 20% potaseium hydroxide, 20% sodium hydroxide, and concentrated sulfuric acid. It was found to be slightly soluble in hot chloroform, benzene, and 90" to 100" petroleum ether. An elementary analysis showed no sulfur, nitrogen, phosphoruq, halogens, or oxygen.
tive (C) (tan, flocculent material) Evaporate acetone; residue ( G ) (black powder)
I1
T r e a t with separate benzene so-, lution and evaporate;] residue ( F ) (pitchlike substance) Approx. yield, 90 mg.
yield, l o mg*
yield. I~-4pprox. ipram
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INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE11. CARBON-HYDROGEN ULTIMATE ANALYSESON PORTIONS OF FRACTION Ea Sample b No. C ?% H, % Ash, % H: C Ratio 0.55 2.023:i la 85.10 14.45 No report 2.021:l Ib 85.80 14.55 N o report 1.965:1 2 85.01 14.02 1.82 1.989:1 3 84.00 14.02 a All carbon-hydrogen analyses were performed and reported b y Clark Microanalytical Laboratory, Urbana, Ill. b Samples l a and lb were prepared b y recrystallization and deoolorization b y charcoal: sample 2 by distillation at 290-310' (1 mm.); sample 3, no pretreatment.
a .
*
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the equation, structures of Cj4HIl0and CrlH~awere found for nparaffLns having melting points of 95.5" and 106O, respectively [mean melting points of the material distilled between 290" and 310" and between 310" and 360" ( 1 mm.), respectively]. These values compare favorably with those determined by Carothers et al. ( 4 ) on synthetic n-paraffins with 40, 50, 60, and 70 carbon atoms,
The same fraction of distillate used for infrared study was taken as an x-ray diffraction powder sample. The resulting film was indexed b y assuming the material t o have an orthorhombic unit cell, the base of which had the dimensions a = 7.45 A. and TJ = 4.97 A. as determined by Muller for the solid n-paraffins (15). On the basis of this assumption, ten lines, including the three strongest, were indexed as hkO "reflections." Although it was not possible to determine the c axis or the chain length from the x-ray film, little doubt remained that the sample was a n-paraffin or a mixture of n-paraffins. A sample of fraction E recrystallized from 90" to 100" ligroin was used for a determination of the refractive index of the solid a t room temperature by using petrographic index liquids and a polarizing microscope. The material was found t o be crystalline and anisotropic. The indexes of refraction lay between 1.531 and 1.535. The low birefringence of 0.004 agreed well with the observed interference color. The largest crystals were 2 microns in diameter. Figure 3.
Close-up of Lower Ends of Extraction Columns
111. VACUUM FRACTIONAL DISTILLATION OF FRACTION E TABLE
@
tl
e
B.P. (1 Mm.), C. Below 290 To 300 To 310 To 320 To 330 T o 340 To 350 T o 360 hIe1ting points are uncorrected.
M.P.a, 95-6 95-6 95.5
On the basis of chemical and physical evidence fraction E has been determined to be a mixture of high-molecular-weight nparaffin hydrocarbons.
C.
105
105.5-107.5 105.5-107.5 103.8-108 106-108
ANALYSIS OF FRACTION F
.4 sample of the material distilled between 310" and 320" ( 1 mm.), melting point 105 ", and recrystallized from butyl acetate was found t o have the same extreme refractive indexes but contained a number of larger crystals. A biaxial positive interference figure with a large optic angle was observed with one large crystal. The observed optical properties of the crystalline material are within the range of similar properties of paraffin waxes as given by Reistle and Blade ( I 7 ) ,Hubbard ( I O ) , and Larsen and Berman (I!?), although the latter authors give paraffin wax and ozocerite as uniaxial positive crystals. The crystals appeared similar to those in the photomicrographs of Reistle and Blade ( 1 7 ) . The material isolated by the authors appeared t o differ only in its unusually low birefringence. A molecular-weight determination of the crude powder (fraction E ) by the modified Menzies-Wright method ( 8 ) gave a value of approximately 1100 (C78H168 for a n-paraffin). The precision of this measurement was low, owing to the small amount of sample available. An empirical formula relating the number of carbon atoms with the melting point for n-paraffins has been given by Meyer and van der Wyk (IS) as (1/Ti = a b/Z), where a and b are constants having values of 2.395 X 10-3 and 17.1 X low3,respectively, Z is the number of carbon atoms in the molecule, and Ti is the melting point in degrees K. Applying
+
This material was insoluble in water, 5% hydrochloric acid, 5% potassium hydroxide, and concentrated sulfuric acid, but partly soluble in ether. It contained no nitrogen, sulfur, halogens, or oxygen. Analyses for characteristic structures of aldehydes, ketones, and aromatic and olefinic unsaturation were negative. Other functional groups were not checked on account of the solubility classification as an inert compound and the ncgative elemental oxygen test. A portion of the sample was dissolved in chloroform and treated with charcoal, which effectively removed most of the color. The solvent was evaporated from the solid in a fractionation tube, and a vacuum distillation was carried out. The bulk of the material distilled as a colorless oil a t about 250" (1 mm.), a small amount of a yellow wax a t 250' to 330 O ( 1 mm.), and a trace of a brown wax a t 330" t o 360" ( 1 mm.). No good melting points were obtained on these fractions. Apparently fraction F consisted largely of a mixture of saturated hydrocarbons of lower average molecular weight than those found in fraction E. The surface activity of a dilute toluene solution of fraction F \ Y ~ B tested by measuring the depression of the toluene-water interfacial tension. A ring tensiometer was used for the measurements. No effort was made to obtain more than qualitative results. The interfacial tension of the solution initially was about 3 dynes per om. lower than that of pure toluene-water, but dropped an additional 4 dynes per om. over a period of about 10 minutes. This was considered evidence that fraction F contained some surface-active material in addition to the hydrocarbons.
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
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ANALYSIS O F FRACTION G
The Rample Fas insoluble in water, ether, benzene, toluene, carbon tetrachloride, 30 to 65 petroleum ether, 5 yohydrochloric acid, 5% and 20% potassium hydroxide, 20y0sodium hydroxide, and 85y0sirupy phosphoric acid. It was soluble in chloroform, pyridine, ethylene dichloride, mesityl oxide, and ethylene glycol nionobutyl ether, somewhat less in acetone, and partly soluble in concentrated sulfuric acid. Solubility classification tests placed the sample in the Shriner and Fuson Class Ns group of neutral compounds including ketones, esters, quinones, ethers, and unsaturates (19). The functional group test for aromatic unsaturation was negative, but that for olefinic unsaturation was positive. Tests for other functional groups have not been performed. Tests for elemental sulfur, nitrogen, halogens, and oxygen were negative. The test for oxygen was considered doubtful, but no good positive test was obtained when repeated on a number of samples. When the sample was burned and heated strongly, a black ash was obtained which appeared to be insoluble in dilute hydrochloric acid. A portion of the material was dissolved in purified chloroform for an interfacial tension measurement. The chloroform solution-water interfacial tension was about 6 to 7 dynes per cm. lower than that of the pure chloroform-water interface. This observation has been interpreted as indicating that fraction G contained surface-active material. O
O
DISCUSSION
The isolation of n-paraffins at the OCW crude oil-water interface was unexpected in view of the fact that their energies of adsorption would be low compared with molecules containing both hydrophobic and hydrophilic groups. It is difficult to postulate a mechanism for such an adsorption process unless the adsorbate molecules are surface active. The results obtained by Bartell and Niederhauser (3) give every indication that the material isolated from their sample of Rio Bravo, Calif., oil was highly surface active. Work a t this laboratory with the Rio Bravo crude confirms their results, but the OCW oil behaves differently. The writers feel justified in describing the isolation process used with the OCW oil as “adsorption,” because adsorption merely implies a concentration of material a t an interface with consequent lowering of the free energy of the system. The designation of adsorption as the extraction procedure implies no pal ticular mechanism. Considerable speculation has been indulged in concerning the nature of the adsorption process, but experimental work has failed so far to establish any one mechanism. Bartell and Niederhauser (3) found, in general, that the petroleum samples they worked with absorbed oxygen from the air and the oil-water interfacial tension dropped after such exposure. The reaction of the OCW oil with oxygen has not been studied, but it has been observed that additional material may be extracted from an exhausted OCW sample if air is bubbled through it for several days. These observations suggest that crude oils may contain labile substances which are more or less readily oxidized t o form minute amounts of peroxides or hydroperoxides which may serve as polar intermediates in the water extraction process. Such substances would be polar and surface active and would migrate to an oil-water interface. The writers do not believe that the n-paraffins isolated in fraction E are film-forming constituents in the sense of the material isolated by Bartell and Niederhauser (3). Nevertheless, the n-paraffins were adsorbed at oil-water interfaces, and it is of interest to postulate some possible mechanisms. The isolated n-paraffins in fraction E were observed to be insoluble in a great variety of organic and inorganic solvents.
Vol. 43, No. 5
This suggests the possibility of their presence in the original crude oil as finely divided microcrystals. A dispersion of fine wax crystals might be stabilized by a protective colloid which could be oxidized easily by air to form a hydrophilic coating around each crystal, such that the particle would be adsorbed at an oil-water interface. The minute amount of oxidizable material might have been undetected in the isolation procedure. Possibly it was responsible for the observed surface activity of fractions F and G. Further work on the problem is being carried out a t this laboratory. The nature of the substance in the OCW oil responsible for tenaciously coating sand grains with a hydrophobic surface remains uncertain. Possibly the coating consisted of n-paraffins of high molecular weight together with resins and surface-active materials. If coatings containing substances as insoluble as the giant members of the n-paraffin family were formed on core samples of oil-field reservoir rock, it would be exceedingly difficult to clean the rock well enough to perform significant flow experiments or accurate routine determinations of interstitial water content. No effort was made to prevent the crude oil used in this work from coming in contact with oxygen. All experiments vier? carried out on samples which were exposed to air. The writers do not presume to believe that wax-containing films are formed at rock interfaces in petroleum reservoirs which are under reducing rather than oxidizing conditions. Nevertheless, the observations reported in this paper are believed to have significance in laboratory experiments where cores and crude oils are studied in the laboratory in contact with air, and in the recovery of petroleum from depleted reservoirs by air and possibly water drive. An unexpected result of this work is the suggested possibility of extracting various high-molecular-weight n-paraffis from some types of crude petroleum in those cases where the extraction process is less difficult than Bynthetic methods previously used. The estimated yield of 0.125 gram of Cw to Cso n-paraffins per liter of OCW crude oil might be adequate for research purposes or the production of fine chemicals. Carothers et al. stated in 1930, “No rationally synthetic and practical methods for the preparation of giant individuals of the simpler homologous series are available” ( 4 ) . No references to any appreciably simpler synthetic methods have been found in the literature since 1930. The isolation procedure described in this paper may be less timeconsuming than chemical synthesis. ACKNOWLEDGMENT
The authors are indebted to the following for valuable discussions concerning this work: W. E. Ilanson of Mellon Institute, Ben B. Cox of the Gulf Research and Development Co., F. T. Gardner, R. J. Kaufmann, and W. L. Nelson of the University of Tulsa, and H. M. Smith of this station. W. W. IIambleton did the microscopic work on the crystalline material. LITERATURE CITED
(1) Abozeid, M., Trans. Ani. Inst. Mining Met. Enyrs., Petroleum Div., 92, 340 (1931). (2) Barr, IT.E., and Anhorn, V. J., “Scientific and Industrial Glass Blowing and Laboratory Techniques,” pp. 284-303, Pittsburgh 12, Pa., Instruments Publishing Go;: 1949. (3) Bartell, F. E., and Niederhauser, D. 0.. Fundamental Research on Occurrence and Recovery of Petroleum 1946-47,” pp. 57-80, New York, American Petroleum Institute, 1949. (4) Carothers, W. H., Hill, J. W., Kirby, J. E., and Jacobson, R. A., J . Am. Chem. Soc., 52, 5279 (1930). ( 5 ) D e Groote, M., “ T h e Science of Petroleum,” pp. 616-29, London, Oxford University Press, 1938. (6) Dow, D. B., and Reistle, C. E., Jr., U. S. Bur. Rlines, Relit. Inuest. 2692 (1925). (7) Fischer, F., and Tropsoh, H., Ber.. 60B, 1330 (1927); Rrennstof-Chem., 8, 165 (1927). (8) Fisher, H. F., Trans. Am. Inst. Mining Mat. Engrs., Petroleum Div.,92, 359 (1931).
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INDUSTRIAL AND ENGINEERING CHEMISTRY
(9) Gascard, A.,Ann. chim., 15,332 (1921). (10) Hubbard, B., Am. Mineral., 30, 645 (1945). (11) Katz, D.L.,Petroleum Technol., 4,17 (1941); T.P. 1400. (12) Larsen, E. S.,and Berman, H., U. S. Geol. Survey, BulE. 848 (1934). and van der Wyk, A. J. A., Helw. chirn. Acta, 20, (13) Meyer, K.H., 1313 (1937). (14) Monson, L.,Congr. mondial petrole. 2rne Congr. Paris, 1937 11, Sect. 2, Phys., Chim., Raffinage, pp. 335-43. (15) Muller, A,, Proc. Roy. SOC.London, A, 120,437 (1928). (16) Power, F. W., IND. ENG.CHEM.,ANAL.ED.,11, 660 (1939). (17) Reistle, C. E.,Jr., and Blade, 0. C., U. S. Bur. Mines, BUZZ.348, 125-58 (1932).
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(18) Shepard, A. F., and Henne, A. L., IND.ENG.CHEM.,22, 356
(1930). (19) Shriner, R. L., and Fuson, R. C.. "Systematic Identification of
Organic Compounds," 2nd ed., New York, John Wiley & Sons, 1940. (20) Stevens, P.G., and Schiessler, R. W., J . Am. Chem. SOC., 62,2885 (1940). RECEIVED July 24, 1950. Presented before the Division of Petroleum Chemistry at the 117th Meeting of the AMERICAN CHEMICAL QocrmY, Houston, Tex. First paper in a proposed series describing studies of film-forming and surface-active constituents naturally present in crude petroleum.
Acetaldehyde, Propionaldehyde, and n-Butyraldehyde SOME PHYSICAL PROPERTIES THOMAS E. SMITH AND ROBERT F. BONNER U . S . Industrial Chemicals, Inc., Baltimore 3, M d . T h e physical data presented in this paper were needed in the development of methods for separating acetaldehyde, propionaldehyde, and n-butyraldehyde from the thirty-odd water-layer chemicals produced from natural gas by the hydrocarbon synthesis process. The literature data on these aldehydes are too discordant to be of any use. The density, refractive index, and vapor pressure of extremely pure samples of each aldehyde have been determined under nitrogen at several temperatures. For propionaldehyde and n-butyraldehyde, the mutual solubility with water at 25" C. and the composition of the aldehydewater azeotrope have also been determined. In addition to these physical data, techniques for purifying, handling, and storing these aldehydes are described, and an improved method for determining their purities is presented. The information given in this paper should be useful to both research and production men working with these compounds.
A
LTHOUGH the aliphatic aldehydes are very reactive and,
4
e
consequently, are commercially important chemical intermediates, little accurate information has been published to date on their important physical properties. The data presented in this paper will partially fill this gap in the chemical literature. The extreme disagreement of available data is probably due primarily to the fact that although these aldehydes undergo rapid oxidation in the presence of air, most observers did not handle them in. an inert atmosphere. This practice may also account for the frequent reference in the literature to the tendency of aldehydes to undergo rapid polymerization. The authors, who kept all samples in a nitrogen atmosphere, encountered no such difficulty. PURIFICATION OF MATERIALS
Acetaldehyde and propionaldehyde of good quality were obtained for this work from a pilot plant operated by the Stanolind Gas & Oil Co. to procure data for the design of a commercial plant for the separation and purification of the hydrocarbon synthesis water-layer chemicals. The n-butyraldeh de used was the best material available from the Eastman Kofak Co. ACETALDEHYDE. The acetaldehyde was purified by distillation, using a borosilicate glass column 25 mm. in outside diameter packed with a/,pinch borosilicate glass helices. The
packed section, which was 100 cm. long, was surrounded by an air jacket made from borosilicate glass tubing 45 mm. in outside diameter. This jacket was surrounded by a water jacket made from borosilicate glass tubing 64 mm. in outside diameter. A well insulated still head rovided with a dephlegmator and B thermometer well was sealex directly to the column. Before the still was charged with acetaldehyde, the air in the system was displaced with prepurified nitrogen. During a distillation, a ositive nitrogen pressure of 1 inch of water was maintained on t1e still by means of a Moore Products Go. Nullmatic pressure regulator attached to a low pressure nitrogen supply line. Ice water was passed through the dephlegmator and condenser, and 18" C. tap water throuqh the column jacket. A heads cut was taken off a t a reflux ratio of approximately 20 to 1, the main cut a t about 8 to 1. The fraction used for the determination of physical constants, which had a constant boiling point of 20.2" C. at 760 mm., was distilled directly into a borosilicate glass receiver and stored a t about 5' C.
PROPIONALDEHYDE. All attempts to purify wet propionaldehyde by fractional distillation yielded a distillate containing 1.9 weight % water, suggesting the existence of an aqueous azeotrope. [Water analyses were made using a modified Karl Fischer procedure (,%).I When the aldehyde was first treated three times with Drierite, however, and then distilled under nitrogen on a 1.3 X 90 cm. Podbielniak column, a product of high purity was obtained. ( A heads cut was taken off at a reflux ratio of 50 t o 1, the main cut at 20 to 1.) The fraction used for the determination of physical data, which had a constant boiling point of 47.9" C. a t 760 mm., was distilled directly into a borosilicate glass receiver and stored a t room temperature. What little literature data are available on the physical properties of propionaldehyde appear t o have been determined on wet material. T o add t o the confusion, the& are indications that the water present partially combines with the aldehyde to form a hydrate whose concentration is a function of temperature. The density of freshly distilled wet propionaldehyde (1.9 weight yo water) was found to increase steadily upon standing. This change could not be attributed to oxidation of the aldehyde, as all work was done and all samples were stored in a nitrogen atmosphere. T o check the effect of storage temperature on the density of the wet aldehyde, the following experiment was performed: A sample of wet propionaldehyde was divided in half, part A being placed in a refrigerator a.t about 5" C. and part B in a 20" C. constant temperature bath. After 24 hours, the density of each sample was determined at 20" C. The samples were then
