adsorbability of uranium on Dowex 50 from the THF-nitric acid medium can be given (3, 4) with respect to the nonadsorbability of iron(III), gold(III), gallium, and other elements on Dowex 50 and also Dowex 1 from T H F and acetone media of similar composition but containing hydrochloric acid in place of the nitric acid used here. The greatest advantage of this CIESE principle over the conventional ion exchange and solvent extraction procedures is that immediately after removal of the “extractable” species as in our case uranium, a further fractionation of the adsorbed metal ions can be achieved on the resin while with, for example, the conventional extraction of uranium with ether from a nitric acid solution a further separation of nonextractable elements is not readily achieved and conditions are also complicated by the
presence of the relatively large amounts of salting-out agents that have to be added to the aqueous phase before the uranium can be extracted with the ether. The advantages of the CIESE method over the conventional cation exchange procedures used for the separation of uranium have already been pointed out in the introduction to this paper and are amply demonstrated by the results presented in Table I. LITERATURE CITED
(1) Faris, J. P., Buchanan, R. F., USAEC, Rept. ANL-6811, July 1964. ( 2 ) Fritz, J. S., Greene, R. G., ANAL. CHEM.36, 1095 (1964).
(3) Korkisch, J . , 2.Anal. Chem., in press. (4) Korkisch, J., Ahluwalia, S. S., Anal. Chim. Acta, in’press. ( 5 ) Korkisch, J., Ahluwalia, S. S., J. Inorg. Nucl. Chem., in press, (6) Korkisch, J., Arrhenius, G., ANAL. CHEM.36, 850 (1964).
G., Talanta 9,957 ( 1 (9) Kraus, K. A., Moore. F. L.. Nelson. F . , J . A m . Chem. SOC.7 8 , 2692 (1956). (10) Nelson, F., Murase, T., Kraus. K. A.. J . Chromatoo. 13., 503 1196 -._ .-.-4). (ll)’Strelow, F. O W . - E., ANAL. CHEM. 32, 1185 (1960). (12) Strelow, F. W . E., J. S. African Chem. Znst. 16, 38 (1963). (13) Strelow, F. W. E., Rethemeyer, R., Bothma, C. J. C., ANAL. CHEM.37. 106 (1965). JOHANN KORKISCH
s. s. AHLUWALIA
Analytical Institute University of Vienna, IX Wahringerstrasse 38 Vienna, Austria RESEARCH sponsored by the International Atomic Energy Agency and the U. S. Atomic Energy Commission under Contract 67/US (AT(30-1)-2623).
Rapid and Precise Determination of Carbon Dioxide from Carbonate-Containing Samples Using Modified Dynamic Sorption Apparatus SIR: Apparatus developed by Nelsen and Eggertsen (IS) for determining the surface area of solids by a continuous flow method has proved useful, with slight modifications, in studies involving thermal decomposition of carbonates and oxide sintering ( I T ) , chemisorption on solid catalysts ( I @ , and pore-size distribution (IO). With further modifications the apparatus can be transformed readily into a sensitive analytical tool for determining the quantity of gas evolved from certain types of samples through thermal or chemical decomposition or by chemical reaction. This paper is concerned with the use of such apparatus in the quantitative determination of carbon dioxide evolved from carbonate-containing samples after acidification. Commercial apparatus, such as the Perkin-Elmer Sorptometer, should pose no problems for the modifications to be described. The extensive literature on carbonate analysis offers a number of methods for quantitatively determining carbon dioxide evolved from a sample. The method generally regarded as standard is that in which the liberated carbon dioxide is absorbed and weighed (11, 18). However, for optimum results this method usually requires 45 minutes to an hour per determination. Examples of other methods that have been used with varying degrees of accuracy, precision, speed, and adaptability include manometric (8, 18), titrimetric (4,7 , 15), gas volumetric ( I ) , dilatometric (S), controlled loss-on-ignition 500
ANALYTICAL CHEMISTRY
(o), infrared ( 1 4 , and gas chromatography ($1. In studies on the thermal decomposition of carbonates referred to above, precursory data were reported in the determination of the carbon dioxide evolved, but the method did not prove as convenient nor as precise as the method outlined in this paper. Here, in brief, carbon dioxide is released within the apparatus after the sample is acidified. The gas is carried by helium through an absorption train to remove water and undesirable acidic gases and then through a thermal conductivity cell. A determination can be made in about 15 minutes. The method is applicable to various sample types ranging from those containing the highest carbonate content to those containing well below 0.1%. Although samples with a carbonate content lower than O . l ~ ,have not been investigated in detail here, consideration of instrumental stability and of the signal generated by small quantities of carbon dioxide under test conditions leaves little doubt that the method can be further extended, even into the parts per million range, if desired. EXPERIMENTAL
Apparatus. A schematic diagram of the apparatus is shown in Figure 1. A thermal conductivity cell assembly (Gow-Mac Model 9193-TE-11) is contained in an oil bath a t 27.0’ =t0.1’ C. A coil of copper tubing, l/h X 18 inches, is attached to each half (reference and
measuring) of the cell assembly and is also immersed in the oil bath to help provide temperature equilibrium for the incoming gas. The reference and measuring detectors form part of wellknown bridge circuitry (Gow-Mac Bulletin TCTH-6-62-311) in which a total bridge current of 140 ma. is supplied by a 12-volt storage battery. An attempt was made to use the more convenient Gow-Mac Power Supply Control Unit (Model 405-C : l), but it did not provide satisfactory current stability for this application. A Sargent Model MR (multirange) recorder equipped with a Disc integrator (Disc Instruments, Inc., Santa Ana, Calif.) is used for recording bridge signals and integrating peak areas. Helium, used as a carrier gas, is delivered a t 10 p.s.i.g. Pressure is maintained by a Cash-Acme (Decatur, Ill.) type A-360 regulator. A needle valve controls helium flow, which is determined and monitored by a soapfilm flowmeter and rotameter, respectively. The U-shaped sample tube, illustrated in Figure 2, is constructed from two 12/5 standard ball joints sealed to a 5-inch section of 12-mm. i.d. glass tubing. A short side arm that accommodates a rubber septum is sealed into the larger portion of the sample tube. The over-all length (between joints) of the sample tube is about 12 inches. Three U-shaped tubes immediately follow the sample tube in the gas flow scheme. The first contains anhydrous magnesium perchlorate for removal of water from the gas stream, the second contains anhydrous copper sulfate for removal of undesirable acidic gases
GAO EXIT
Figure 2.
(primarily nyurogen cnionae), and the third helps provide sufficient volume in the exit line following the sample tube. The importance of the latter will be discussedlater. Drying tubes (Schwartz type) with 14/20 standard taper hollow glass stoppers and side connecting tubes are convenient for these purposes. Connecting lines between drying tubes and between glass and copper tubing are of Tygon (U. S. Stoneware Co., Akron, Ohio). Reagents and Samples. Primary standard anhydrous sodium carbonate (No. 7528, Mallinckrodt Chemical C o . ) . This was heated at 285' C. for 2 hours before using for calibration. The manufacturer's specification for sodium carbonate assay after this treatment is 99.95-100.05%. Reagent grade hydrochloric acid, 6M. Standard samples: U. S. Geological Survey Diabase
w-1. U. S. Geological Survey Granite G-I. NBS Fluonpar No. 79. NBS Argillaceous Limestone No. la. NBS Dolomite No. 88. A nonstandard soil sample designated
RSOQO. Procedure. A quantity of sample, fine enough t o pass a 60-mesh screen and dried for 1 hour at 110' C.. is
transferred into the sample tube and weighed with a reproducibility of +0.03 mg. I n general, a sample size of 0.14.2 gram is adequate. A 0.1-gram sample of calcium carbonate, for example, when decomposed releases over 20 ml. of carbon dioxide within the apparatus and, as is wellrecognized, this volume of gm can generate a considerable signal in a thermal conductivity measuring system of the type described here. The use of larger samples may be desired when the carbonate content is very low. The ball joints of the ssmple tube are greased lightly, and the tube is attached t o coinciding socket joints by pinch clamps. The system is purged with helium at the controlled flow rate used during calibration (see below) until the air is expelled and a constant base line is produced on the recorder chart. The latter indicates that the system is at equilibrium, with helium alone flowing over both detectors. The bridge is balanced at the zero point where the integrator pen also traces a constant hnse line. When this adjustment is completed, the %way stopcock preceding the sample tube is turned t o divert the helium flow, thereby isolating temporarily the sample tube and the rest of the downstream line from the helium source. Sufficient hydrochloric acid (about 1.5 ml.)
Sample tube
is injected through the septum of the sample tube t o completely cover the sample. Air bubbles must be eliminated from the syringe before the acid is injected. After the syringe is withdrawn from the septum, a beaker of hot water (about 80' C.) is immediately raised into position around the lower portion of the sample tube to increase the decomposition rate. The sample tube is shaken manually t o effect rapid and complete contact of the sample with acid. This process, of course, is facilitated by the balland-socket joints. When decomposition is complete (less than a minute), as is evident by the cessation of bubbles rising from the sample through the volume of acid, the 3-way stopcock is turned to the original position where the helium flow is resumed throughout the system. The carbon dioxide is then carried over the measuring detector and the area of the ensuing symmetrical peak is related through calibration t o the quantity of carbon dioxide evolved. During decomposition, the carbon dioxide expands against the helium forcing some of the latter from the exit line. Sufficient volume in the line between the sample tube and measuring detector is necessary to accommodate the volume of carbon dioxide released. The carbon dioxide must not diffuse t o the measuring detector until the helium flow is resumed. I n the apparatus described, the volume occupied by helium in this line is approximately 150 ml. This is more than adequate t o satisfy this requirement. The base line remains constantnecessity for accurate w o r k a u r i n g the operations just outlined. Generally, no lower recorder range than 0-25 mv. (full scale) is needed to record the signalgenerated and provide an adequate VOL 38,
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peak for analysis purposes, except when very small quantities of carbon dioxide are to be measured. Calibration. Figure 3 illustrates the calibration curve obtained under the given conditions by decomposing primary standard sodium carbonate. A 0.1-gram sample of this standard yields 41.52y0 by weight (over 21 ml. at S.T.P.) of carbon dioxide. Considering such factors as detector sensitivity, signal generated, and apparatus design, this quantity is in the upper range of that desired for calibration. Consequently, in order to keep weighing errors below O.l%, the lower portion of the curve was established with samples weighed to the nearest 0.002 mg. At the lower end of the curve, the detector response to varying quantities of carbon dioxide approaches linearity. This is true even if more sensitive recorder ranges are used in which a proportionately larger number of integrator counts are obtained per given quantity of carbon dioxide. Thus, in the analysis of very low Carbonate-containing samples where, as a general rule, the relative error becomes less important, a linear calibration may be used that is based simply on the establishment of integrator counts per milligram of carbon dioxide from one or two carefully weighed standard samples. RESULTS AND DISCUSSION
The method was tested on selected National Bureau of Standards samples and on two U. S. Geological Survey sample\ generally accepted a5 standards (16). Reiults .hewn in Table I are in excellent agreement with the mean of accepted valuer obtained by the different analysts that participated in establishing each substance as a standard. The method is senqitive and quite reproducible for samples of low carbonate content, greatly exceeding the reproducibility normally associated with such analyses. Considering sensitivity, approximately 0.43 mg. of carbon dioxide (from about 1.4 mg. of sodium carbonate) gives a peak area of about 3100 counts on the 0-2.5 mv. recorder
Table 1.
WEIGHT i m g l
Figure 3. Calibration curve Recorder range, 0-250 mv. Gas flow rate, 50.8 ml./rnin. Bridge current, 140 ma.
range. An entirely satisfactory peak area of 310 counts would be observed for a tenth as much (about 0.04 mg.) carbon dioxide. If necessary, the sensitivity may be increased by increasing the bridge current. The same carefully controlled conditions that are used in the calibration must be maintained during an analysis. Small changes in bridge current and in gas flow rate will cause appreciable changes in the response of thermal conductivity detectors (5, 6 ) . Sufficient volume provided between the sample tube and the measuring detector, coupled with the diversion of helium flow during sample decomposition, provides an absolute safeguard against errors that would arise if detection were to occur while the sample continued to give off carbon dioxide. Diversion of helium flow during sample decomposition minimizes diffusion of carbon dioxide, thereby providing sharper peaks with little tailing. The decomposition step does not take nearly as long to complete as one might
anticipate. Less than a minute was required for all of the samples reported here. An appreciably longer period of time was necewary for 60-mesh single-crystal cleavage pieces of magnesite (magnesium carbonate), but 60mesh particles of fine grained magnesite decomposed rapidly in the slightly heated acid once decomposition had begun. Soil, clay, and shale samples may be handled in the same manner. Because it was thought that a soil sample might be somewhat less than ideal for rapid decomposition of the carbonate constituents, several runs were made on the soil sample designated R-5090. Table I1 shows the excellent precision obtained with the varying sample weights and affirms the adequacy of the decomposition step. A number of other similar samples have been run in duplicate and excellent agreement was found between the results obtained for each pair. The apparatus and procedures outlined in this paper should be useful in certain ot'her gas analyses. If more than one gas is evolved during a particular
Carbon Dioxide Results b y the N e w Method in Comparison with Accepted Values for Carbonate-Containing Standard Samples
Carbon dioxide found, yo
Accepted values, yoa 33.66, 33.40, 33.42, Alean 33.54 33.67, 33.40, 33.67 Std. dev. 0.11 33 Range 33.36-33.65 _ _ 57 .. 47.25 47.34, 47.51, 47.46 Mea: NBS 88 Dolomite 0.98 0.972, 0.981 Mean NBS 79 Fluorspar Std. dev. 0.029 Range 0.92-1.01 0.08 0.0717, 0.0715, 0.0725 Mean U.S.G.S. G-1 Granite Std. dev. 0.01 Mean 0.06 0.0581 U.S.G.S. W-1 Diabase Std. dev. 0 . 0 3 a Taken from Certificate of Analyses for NBS samples and from U.S.G.S. Bulletin 1113 for the U.S.G.S. samples.
Sample no. NBS l a
502
OF CARBON DIOXIDE
Type Argillaceous limest one
ANALYTICAL CHEMISTRY
Table 11.
Carbon Dioxide Results for Soil Sample R-5090
Sample Run no. weight, grams 1 2 3 4 5
Carbon dioxide, you
0,1730 0.1861 0.1428 0.1366 0.1152
5.144 5.136 5.124 5.132 5.129 Av. 5.133 Std. dev. 0.0075
a Duplicate results by classical gravimetric procedures were 4.99 and 5.17.
decomposition, a judicious choice of absorption tubes or cold traps placed in the system should permit the detection and measurement of the one gas of primary interest. ACKNOWLEDGMENT
The authors are indebted to Donald R. Dickerson, David B. Heck, and Sei1 R. Shimp for their helpful discussions and assistance during portions of this work. LITERATURE CITED
(1) Bessey, G. E., J . SOC.Chem. Znd. 5 8 , 178 (1939). ( 2 ) Carpenter, F. G., AXAL.CHEM.34, 66 (1962).
(\ 3- ,) Clarke. B. L.. Hermance. H. W.. IND. ~
~
ENG.CHEM.,ANAL.ED. 9, 597 (1937). (4) Colson, A. F., Analyst 6 5 , 638 (1940). ( 5 ) Daeschner, H. W., Stross, F. H., ‘ ANAL.C H E ~ 34, . 115i) (1962): (6) Dimbat, M., Porter, P. E., Stross, F. H., Zbid., 2 8 , 290 (1956). (7) Doerffel, K., Chem. Tech. 6,391 (1954). (8) Fuller, C. H. F., Analyst 70, 87 (1945). (9) Galle, 0. K., Runnels, R. T., J . Sediment. Petrol. 30, 613 (1960). (10) Haley, A. J., J . A p p l . Chem. (London) 13, 392 (1963). (11) Hillebrand, W. F., Lundell, G. E. F., “ADdied Inorganic Analvsis.” ” , .D. 623. a i i & , New Ygrk, 1929. (12) Kolthoff, I. AI., Sandell, E. G., “Textbook ’ of Quantitative Inorganic Analysis,” 3rd ed., p. 372, hIacmillan, Xew York, 1952.
(13) Pielsen, F. &I., Eggertsen, F. T., ANAL. CHEM.30, 1387 (1958). (14) Pobiner, H., Ibid., 34, 878 (1962). (15) Schollenberger, C. J., Whittaker, C. W., Soil Sci. 8 5 , 10 (1958). (16) Stevens, R. E., and others, U. S. Geol. Survey Bull. 1113, 126 pp., (im). (17) Thhmas, J. Jr., Hieftje, G. M., Orlopp, D. E., ANAL. CHEY. 37, 762 (1966). (18) Williams, D. E., Soil. Sci. SOC.Am., Proc. 13, 127 (1948). (19) Wise. K. V.. Lee. E. H.. ANAL. ‘ CHEX 34, 301 (1962).‘ \ _ _ . _
JOSEPHUS THOMAS, JR. GARYhl. HIEFTJE Illinois State Geological Survey Natural Resources Building Urbana, Ill. 61803
Fructose-Reso rcin01-H yd rochlo ric Acid Test for Detection and Determination of Acetaldehyde SIR: While investigating various procedures to determine fructose by means of the resorcinol-hydrochloric acid test, we found that the wavelength of maximum absorption (Amax) was shifted from 480 mp to 555 mp when acetaldehyde was incorporated in test mixtures which contained a high concentration of hydrochloric acid (2, 8). R e used this finding to develop a new, highly sensitive test for the qualitative detection or quantitative determination of acetaldehyde. The purpose of the present communication is to describe this new test which provides an alternative with different specificity to the sodium nitroprusside test for acetaldehyde (.$).
cooled for 1.5 minutes in an ice bath, and the absorbance was measured 10 minutes later at 555 mp against a blank in which water had been substituted for the acetaldehyde solution. Procedure for Qualitative Detection. The same procedure as for the quantitative determination was used except t h a t the rigid time schedule was not required. T h e test solution and the blank were heated for 10 minutes at 80’ C. or for 2.5 minutes in a boiling water bath, cooled in a n ice bath, and compared visually. A positive test was indicated by a red tinge to the test solution. The blank was light-orange.
EXPERIMENTAL
The absorption spectra of colored solutions obtained using a procedure comparable t o that described above have been published ( 2 ) . The absorption spectrum of EL test mixture containing acetaldehyde, after correction for the blank, has maximum absorbance at 555 nip. The curve of color development showed that the absorbance of 555 mp reached its maximum and \yas constant between 9 and 12 minutes of heating at 80” C. It decreased thereafter with longer heating time. Fading of the color after completion of the test was almost linear during the first hour, being 87, after one hour in artificial light or in the dark. The color fades drastically on exposure t o sunlight. Beer’s law was adhered to for solutions containing up to 100 mpmole of acetaldehyde per ml. As expected from previous results ( 2 ) , the slope of the straight line increased slightly when acetaldehyde was diwolved in purified acetic acid rather than in mater. The amount of fructose (0.4 pmole) in the
Apparatus and Reagents. Absorbance measurements were made with a Beckman DU spectrophotometer and 1-cm. borosilicate glass cells. Acetals, aldehydes, and acetone were purchased from commercial sources, and all liquids were purified by distillation prior to use. The resorcinol reagent was prepared just before use by adding 100 ml. of concentrated hydrochloric acid (specific gravity 1.188-1.192) to 10 ml. of aqueous resorcinol stock solution (1.2 x lO-?JI). Procedure for Quantitative Determination. The reaction was carried out in diffuse light. T o a boiling tube (25 X 150 m m . ) was added 1 ml. of 4.0 X 10-4JI fructose solution and 1 ml. of acetaldehyde solution. The tube was covered with a glass marble, cooled in an ice bath for a t least 3 minutes, and the resorcinol reagent (10 ml.) was added. The contents were mixed in the ice bath and cooled for a further 3 minutes. The tube was placed in a water bath a t 20” C. for 4 minutes, heated for 10 minutes a t 80” C.,
RESULTS AND DISCUSSION
proposed procedure was selected because if affords the best compromise between sensitivity of the test, range of adherence to Beer’s law and size of blank. The .mallest amount of acetaldehyde which may be visually detected is 10 mpmole per ml. or 0.4 p.p.m. The respor se of carbonyl compounds and acetal3 cnder standard test conditions may be divided into four groups and is shown in Table I. Group I comprises acetaldehyde and 1,l-diethoxyethane which afford identical results within experimental error. 1,lDiethosyethane is hydrolyzed to acetaldehyde under test conditions. Group I1 is made up of propionaldehyde and butyraldehyde which, if present, would invalidate the determination of acetaldehyde. It is probable that higher n-aliphatic aldehydes would also interfere. Compounds with a phenyl ring are placed together in group 111. M‘hile these compounds might interfere somewhat with the determination of acetaldehyde, their presence in mixtures can always be detected as they have a different position of A,, (Table I). Other carbonyl compounds are included in group IV. These compounds will not cause interference unless their concentration greatly exceeds that of acetaldehyde. The acetaldehyde content of eight brands of 99.5+% acetic acid as determined by the fructose-resorcinolhydrochloric acid test varied from 10 to 486 mpmole per ml. Acetic acid prepared by present methods ( 5 ) should contain no aldehyde other than acetaldehyde. S o trace of propionaldehyde or butyraldehyde was found in the single brand of acetic acid examined earlier ( 2 ) . The single brand of absolute ethanol analyzed contained 195 mpmole of acetaldehyde per ml. VOL. 38, NO. 3, MARCH 1966
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