1000
INDUSTRIAL AND ENGINEERING CHEMISTRY
upward until it reads correctly for some one calculated correction. Mathematical treatment of Charles' law will lead to volume corrections due to temperature changes : Vo= -V_ To
vo 4- AV
T - T o + AT
A nomogram similar to the previous one is constructed. For any ordinary room temperature changes it can be used to give corrections with a high degree of accuracy, although mathematically it is not exactly true. This is due to the term AT' subtracted from V in the last equation. This is not a serious error, however, for an increase of 3" C. from standard is a temperature change of only about 1 per cent. Thus there would be an error of 1 per cent in the volume correction, which is in itself only about 1 per cent of the
VOL. 32, NO. 7
volume. In other words, the corrected volume would read about 0.01 per cent low, well within any limits of reading gaseous volumes in any analytical work. Even as drastic change as 5" C. would cause an error of only about 0.03 per cent. Figure 2 illustrates an alignment chart used in this laboratory to refer volumes to 22" C. For temperature changes of less than 0.5" C. i t is still usable, for changing AT by a factor of 10 changes A V by the same factor. When both ?' and P differ from standard, corrections are read from each scale and their algebraic sum is added to the observed volume.
Literature Cited (1) Allcock and Jones, "The Nomograph", Chap. 11, London, Sir Isaac Pitman & Sons, 1932. (2) Barr, G., J. Soo. C h . Id.,49, 21-3T (1930). (3) Blacet and Leighton, IND.ENQ.CHEM., Anal. Ed., 3, 266 (1931). PUBLISHED with the approval of the Monographs Publication Committee, Oregon State College. Research Paper 33, School of Science, Department of Chemistry.
Liquid-Vapor Equilibria of Furan Systems J
A. P. DUNLOP AND FLOYD TRIMBLE The Quaker Oats Company, Chicago, Ill.
-1TH the increasing market for furfural, furfuryl alcohol, and tetrahydrofurfuryl alcohol, it seems desirable to extend our present knowledge regarding liquid-vapor equilibria of binary or ternary mixtures in which one or more of these products is present. With the exception of the data given by Mains (4) on the system furfural-water and by Lecat (2) regarding azeotropic mixtures, a survey of the literature revealed little information of this nature.
W
Procedure The furfural and furfuryl alcohol were prepared by fractionating the technical grade of each, three times under vacuum. The fractionating column was a well-insulated, 7-foot (2.13-meter) Hempel column, packed with 7-mm. glass Raschig rings. The apparatus was constructed entirely of glass, with ground-glass connections. Discards of approximately 15 per cent of the total volume were made a t t,he beginning and end of each distillation, and the mid-fractions which were used in this study boiled over a range of 1" C. The following physical constants were determined : Roiling range at 25 mm., C. Specific gravity, d:: Refractive index, ny Moisture (Bidwell-Sterling method) yo Acidity (chcd. as acetio acid), %
Furfural 64-65 1.1584 1.5255 0.0 0 002-0.003
Furfuryl Alcohol 83-84 1,1321 1.4868 0.0
0.002-0.003
The apparatus used for determining the liquid-vapor equilibria (Figure 1) was similar to that employed by Othmer ( 5 ) . Certain modifications were made, however-namely, trap F and condenser C'. The former was designed to
The System FurfuralFurfuryl Alcohol prevent the boiling liquid from surging over into the distillate receiver, and condenser C' was necessary to avoid undue losses of vapor when operating under vacuum. The furfural-furfuryl alcohol solution was boiled in still body A , the vapors passing through inner tube B and condenser C to be collected as distillate in receiver D. As the distillation proceeded, the temperature increased gradually until the contents of the receiver overflowed into the still body. At this stage the temperature decreased slightly as a result of the introduction of the distillate which was relatively richer in the more volatile component. Inasmuch as the overflowing distillate has the same composition as the vapors being evolved, the composition of the boiling liquid in the still body eventually reaches a constant value. When this condition is attained, the temperature ceases to fluctuate; but before the distillate is drawn off for analysis, the process is allowed to continue until approximately three times the volume of receiver D has overflowed into the still body. The distillate was then assumed to be representative of the vapor which existed in equilibrium with the liquid composition. At no time was the volume of liquid in still body A less than 250 cc., and the volume of distillate collected was approximately 10 cc. The pressure was maintained a t 25 mm. of mercury by means of a Hyvac pump which was connected to the top of condenser C'. A preliminary investigation of the system when distilled at atmospheric pressure indicated that prolonged heating had an adverse effect on solutions of furfural and furfuryl alcohol as measured by refractive index. The magnitude of this effect is shown in Table I and Figure 2, the data being obtained by refluxing solutions of known concentration a t atmospheric pressure for the indicated time.
9
JULY, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
lo01
TABLEI. EWPECT OF KEFLWXING F c m a ~ - F u a ~ mAW u~ CONOL SOLUTJONS AT AThIoSPHERlC PRESSmtE -Rdraotivo PorCent No Furfural heating 0.00 1.4868 4.00 1.4891 8.49 1.4905 10.49 1.4925 14.08 1.4955 16.91 1.4946 22.03 1.4965
--Reirsetive
Index,nw-
Re 1 hi.
ReRured Per Cent 2 hr. Furfursl 1.4890 1.4893 58.03 1.4915 1.4956 44.81 .,. ... as.39 ... ... 08.27 ... 76.71 1:4990 ... 100.00 fluxed
...
...
Index, d Re fluxed
ReRured hcalmr 1 hr. 1.6015 1.5077 1.5000 1.5102 1.5129 i:biea 1.5180 1.5204 1.5255 l.GZ56
Nq
...
2 hr. 1.5103
...
1:$iS7 1.5222 1.5256 ~
TAB^ 11. LIQUID-VAPORE~url.m~r4OF FnmomL-FunFUHYL
A ~ c o i r oAT~ 25
Liquid Phase PPIcent Mole fraction furfural furfural
MM.
Vapor Phsse Per cent Mole fraetioo furfural furiurd
It WES found, howcver, that furfural-furfuryl alcohol solutions could be heated at 100' C. for one hour with no chmge in the refractive indices. For this reason the present investigation was conducted at 25 rum. of mercury, at which pressure the system boils in the range 64-84" C., depending upon the composition of the solution.
FIQDRE 3. EQUILIBRIUM RELATIONS FOR 'I'I
