ANALYTICAL CHEMISTRY
414
Table I.
Analysis of Known Blends of Furfural in Oil
Blend No. 1
2
3 4 5 6 7
8 9
Furfural, % Added FounT
Difference, %
+-0.0001 0,00002
0.00020 0.0010 0.0010 0.0010 0.0010
0,00022 0.0009 0.0009 0.0010 0.0010
0.0030 0.0080 0.014 0.060 0.100 0.100 0.100 0.100 1.00 1.00
0.0033 0.0080 0.015 0.060
+0.0003 0 0000 +o 001 0.000
0.098 0.10 0.098 0.10 1.03 0.93
-0.002 0.00 -0.002 0.00 $0.03 -0.07
-0.0001 0,0000 0,0000
slit width of about 0.6 mm., using water in the reference cell. If the absorbance is above 0.8,this solution should be diluted. Determine the reagent blank, using only iso-octane and the reagents and carrying them through all the operations. Subtract the absorbance of the reagent blank from that found on treatment of the sample. From the net absorbance and the analytical curve determine the milligrams of furfural and calculate to percentage in the sample. DISCUSSION
To ensure greatest accuracy, all standards should be prepared either from freshly distilled furfural or from dilute solutions of furfural in iso-octane, as the latter appear to remain stable and, therefore, do not have to be freshly prepared for each determination.
I n decomposing the addition prodact, excess potassium hydroxide must be added because a t 277 mp sodium bisulfite interferes with the measurement of furfural. The most reliable results are obtained by testing the final alkaline solution within 0.5 hour after preparation. If emulsions are formed during the extraction procedure, they may be broken by being alloiyed to stand, by gently disturbing with a glass rod, or by filtering. The single extraction procedure is sufficient, as shown by the fact that the absorbance of a second extraction of the same standard was not significantly different from the absorbance of the reagent blank. RESULTS
Table I is typical of results obtained on blends of oil with known quantities of furfural. ACKNOWLEDGMENT
The authors are indebted to Henry Chaya, Emil Poti, Raymond D o h , and R. H. Gaddy for their assistance in the preliminary work on this method. LITERATURE CITED
(1) Dunstan, Sonia, and Gillam, A. E., J . Chem. Soc., 5, $140 (1949). (2) Fuchs, L., Monatsh., 81, 70-6 (1950). (3) Javes, A. R., Proc. A m . Petroleum Inst., I I I , 29M 39-41 (1949). (4)
Stillings, R. A., and Bron-ning, R. L., ISD. ENG.CHEM.,ANAL.
ED., 12, 499 (1940). ( 5 ) TVahhab, A,, J . Am. Chem. Soc., 70, 3580-2 (1948). (6) Woelfel, TV. C., Good, W. D., and Keilson, C. A,, Petroleum Eng., 24, S o . 7, C-42 (1952). RECEIVLD for review June 22, 1953. Accepted September 2 5 , 19.53.
Refractive Indices of Some Morpholine Solutions CHARLES M. WHEELER, JR.,
and
CONRAD G . HOULE N. H.
University o f N e w Hampshire, Durham,
ORPHOLINE, being both an ether and an amine, isaversatile solvent and, consequently, enjoys many commercial uses both alone and in combination with other solvents. For this reason, a rapid method of determining the concentration of binary morpholine solutions would be useful. I n view of the limited data reported for binary systems containing morpholine, a number of important morpholine solutions mere investigated to determine the feasibility of using refractive index measurements for rapid analysis of the solutions. Wilson (6) and Greenberg ( 2 ) have reported liquid-vapor equilibrium data for the systems morpholine-water and morpholine-o-xylene, respectively. However, neither author indicated the method he used to determine concentrations of the morpholine solutions. In spite of the well-known solvent power of morpholine, there are no other reported data for binary morpholine systems. The present paper reports refractive index data which may be used for determining the compositions of binary solutions of morpholine-aniline, morpholine-benzene, morpholine-ethyl alcohol, and morpholine-water. These data might be used commercially for rapid accurate determinations of the concentrations of binary morpholine solutions. The authors have used these data in determining concentrations in liquidvapor equilibria studies of binary morpholine systems. Although refractive index values for the pure components of these binary solutions have been reported (1, 3-5, 7 ) no refractive index data for these binary systems are found in the literature. PURIFICATION O F MATERIALS
Morpholine waa fractionally distilled a t 128.1' C. and 758.7 m. (corrected), through a Fenske-packed column of 25 theo-
retical plates. I n order to prevent the contamination of morpholine with carbon dioxide, the distillation was carried out in a closed system and the distillate receivers were vented through Ascarite-filled drying tubes. The aniline and benzene used were fractionally distilled; corrected boiling points of the fractions used were 184.57' C.
Table I.
Refractive Indices of Pure Components
Aniline Morpholine
Experimental, n $o
Literature, n $o
1.5861 1,4547
1 58629 1 ,4545
n
Benzene Ethyl alcohol Water
Table
11.
L5
1.49807 1.35929 1 ,33250
Indices of Solutions
Experimental Data Aniline, Refractive index, weight % n D a t 25,00° C.
(6)
(1)
n k5
I
1.4979 1.3593 1.3327
Refractive
Reference
( 7)
(9)
(4)
Morpholine- Aniline
Smoothed Values Aniline, Refractive index, weight % n~ a t 25.00° C.
415
V O L U M E 2 6 , NO. 2, F E B R U A R Y 1 9 5 4 Tahle 111. Refractive Indices of Morpholine-Benzene Solutions Experimental D a t a Refractive index, Benzene, n D a t 25 00’ C. weight % ’
-
0
1 ,4528
10.9 23.0 31.2 40.3 50.6 63.7 71.7 85.2 92.2 100.0
1.4587 1,4647 1.4685 1,4727 1,4770 1.4828 1.4862 1.4920 1.4949 1.4979
~~~
Smoothed Values Refractive index, Benzene, weight % n g a t 25 00’ C. 0
1 ,4528
10 20 30 40 50 60 70 80 90 100
1.4582 1.4631 1.4679 1.4725 1.4768 1.4812 1.4855 1.4898 1,4940 1.4979
~~~
Table IV.
Refractive Indices of Morpholine-Ethyl Alcohol Solutions
Experimental D a t a Ethyl alcohol, Refractive index, weight % ’ n~ a t 25.00° C. 0 10.9 21.2 29.2 44.7 .53.4
60.2 70.8 80.1 89.1 100.0
Table V.
1.4528 1.4430 1.4337 1.4267 1.4121 1.4040 1 ,3973 1.3872 1.3786 1 ,3700 1.3593
4.5
9.0 12.9 17.1 20.9
25.2 29.7 34.7 38.3 49.5 60.1 71.1 80.2 92.5 100.0
0 10 20 30 40 50 60 70 80 90 100
1.4528 1.4441 1.4352 1,4260 1.4168 1.4071 1.3977 1.3880 1.3784 1.3688 1.3593
Refractive Indices of Morpholine-Water Solutions
Experimental D a t a Water, Refractive index, weight % n D a t 25.00° C.
n
Smoothed Yalues Ethyl alcohol, Refractive index, weight % ’ n D a t 25.00° C.
Smoothed Values Water, Refractive index, weight % R D a t 25.00° C.
1,4528 1.4514
0
1 ,4490
10 15
1.4471 1.4448 1.4407 1.4368 1.4313 1.4253 1 ,4208 1.4044 1.3899 1.3734 1.3600 1.3428 1.3321
5
20 30 40 50 60 70 80 90 100
1.4828 1.4508 1.4486 1.4456 1.4417 1.4310 1.4180 1.4040 1.3896 1.3754 1.3606 1,3464 1.3327
and i M . 0 mm., and 80.20” C. and 762.4 mm., respectively. \Vatcr used in the morpholine-water system was purified in a conductivity still and boiled under vacuum in order to ensure iwnoval of carbon dioxide. I(:thyl alcohol (Roesville Gold Shield alcohol, Coniinercial Solvcbnts Corp.) waa used without further purification.
Table I lists the refractive indices of the compounds used and the literature values are shown for comparison. PREPARATION O F SOLUTIONS AND REFRACTIVE INDEX DETERMINATIONS
Solutions of varying morpholine concentration were prepared by pipetting morpholine into 25-ml. glass-stoppered weighing bottles containing a weighed amount of the other component of the binary system. The actual amounts of each constituent added were determined by weighing to 0.1 mg. on an analytical balance. A Zeiss Abbe refractometer was used to measure refractive indices. According to the manufacturer, the refractometer readings are furnished with a degree of accuracy of about 2 units of the fourth decimal. A constant temperature bath and circulating pump maintained temperature a t 26.00”, with a variation of &O.0lo C. which was observed on a calibrated Beckman thermometer. A temperature control of no better than 1 0 . 2 ’ C. is required for an Abbe-type refractometer. The temperature of the refractometer prisms was measured by a calibrated thermometer, inserted in the prism jacket. Large scale plots of t’he refractive index data were prepared and values were obtained a t even composition increments, from smooth curves through the points. The maximum experimental deviation from the smoothed rurves was 4 X lo-‘ unit, corresponding to a composition difference of about 0.2% by weight. The general experimental deviation was 2 X unit, allowing for an accuracy of =kO.lOj, by weight in determining concentrations. I t is possible to use these reported data for the determination of concentrations of the binary morpholine solutions studied over the entire concentration range with one exception. I n the morpholine-mater system the refractive index of the mixture changes very slowly in the 0 to 20% by weight water region. This small change does not allow for accurate composition determinations by the refractive index method in this region. Experimental data and smoothed values are presented in Tables I1 to T:. LITERATURE CITED
(1) Dermer, V. II., and Dermer, 0. C., J . Am. Chem. Soc., 59, 1148
(1937). (2) Greenberg, R. B., U. S. Patent 2,313,537 (1943). (3) Smith, T. E., and Bonner, R. F., ANAL.CHEM.,24, 517 (1952). (4) Tilton, L. W., and Taylor, J. K., ,J. Research Natl. Bur. Standards, 20, 419 (1938). (5) Washburn, E. W.,Ed., “International Critical Tables,”’ Vol. VIL, New York, McGraw-Hill Book Co., 1929. (6) Wilson, A. L., Ind. Eng. Chem., 27, 867 (1935). (7) Wojciechowski, M., J . Rcsearch S a t l . RUT.Standards, 19, 347
(1937). R E C E I V Efor D review July 17, 1953.
Accepted October 19. 1953.
Electronic Coulometer K E N N E T H W. K R A M E R ’ and ROBERT B. FISCHER Indiana University, Bloomington, lnd.
S
ISCE the enunciation of Faraday’s laws of electrolysis in
1832-33, several different types of coulometers have been devised. Among the more prominent ones have been weight coulometers using silver or copper, volume coulometers using mercury or which decompose water to hydrogen and oxygen, and titration coulometers of iodine, vanadium, and sodium. Although several of these have proved useful, even in extremely accurate work, recent developments in analytical chemistry have suggested the need for some more practical coulometers. One new electronic millicoulometer has been reported in the literature (f), in which current integration is achieved with a direct current motor whose armature oscillates, rather than rotates completely. The rate of angular motion of the armature is pro-
’ Present address, U. 6. 55,386,677, Detachment 2 , Army Chemical Center, hl d
portional to the current flowing through it; so the frequency of oscillation is proportional t o the current. The oscillations of the armature are registered on a commercial scaling unit. An electromechanical integrator has also been reported (2), in which a mechanical ball and disk integrator is controlled by a pen drive mechanism from a n ordinary recording potentiometer. The circuit diagram for another new type of electronic coulometer is shown in Figure 1. The circuit is basically a classical thyratron relaxation oscillator with a special frequency control such that the total number of discharges through the thyratron over a period of time is proportional to the total quantity (coulombs) of current flowing through a resistor during that period of time. The current to be summed up is passed through resistor RB,thus influencing the grid-cathode potential of the control tube, the 657. This grid-cathode potential determines the effective cathode-plate
