Determination of Periodic Acid in Highly Colored Solutions MANNING A. SMITH and BENNETT R. WILLEFORD, JR. Bucknell University, Lewisburg, Pa.
P
ERIODIC acid has long been known t o react quantitatively with 1,2-glycols and their oxidized derivatives arcording to the following equation:
I I -C-OH I
-C-OH
1 + HI04 -c=o + HIOj + H,O -c=o -+
I
This reaction has been discussed by Smith (16), and the work up to 1942 has been reviewed b y Jackson ( 4 ) . OH
/
I
I1
When flavonol(1) and related compounds such as quercetin(11) are treated with periodic acid, highly colored solutions are produced. It is impossible t o determine directly the amount of periodate consumed b y these compounds, for the color of the solutions masks the starch iodine end point on which the analytical method depends. For this reason, a method of making these determinations was sought. This paper reports an investigation of the possibility of separating the excess periodate from the colored organic degradation products by means of an ion exchange resin. For a successful separation, conditions under which the resin retains the periodate ions but not the less acidic organic reaction products and a method of quantitatively recovering the periodate from the resin must be found.
the resin bed. The reaction mixture was then poured on the column and allowed to flow through slowly. A nominal flow rate of 1 ml. per minute was used for the small column runs and 3 ml. per minute for the large column runs. The reaction flask and the funnel were washed well first with the solvent and then with water, and the washings were added to the column. The column was then washed again with water. All of the column effluents for these adsorption and washing stages were tested qualitatively for periodate except in those cases in which the color of the solution precluded such a test. In all runs reported here, these tests were negative, indicating that this procedure resulted in the quantitative removal of periodate from the reaction mixture. The periodate was then eluted from the column with 5% potassium hydroxide solution a t a flow rate of 2 ml. per minute for the small columns and 5 ml. er minute for the large columns. The column effluents were anagzed as described below. The total volume of effluent collected was about 150 and 500 ml. for the small and large column runs, respectively. Analytical Method. Periodate analyses were performed according to the standard method which has been described by Jackson ( 4 ) or Smith (16). Sulfuric acid (2N) was added to the strongly alkaline column effluent until the solution was barely pink to phenolphthalein. Addition of solid sodium bicarbonate (0.1 to 0.5 gram) discharged the color. An accurately measured excess of standard arsenite solution and 2 ml. of 20% potassium iodide solution were added and the solution was allowed to stand for 10 minutes. The excess arsenite was then titrated with standard iodine solution, starch being added near the end point.
Table I.
Rlln
Periodate added, rl,i~oles Effluent c u t 1. volume, ml. IO4-found, minoles C u t 2, volume, ml. 1 0 4 - f o u n d mmoles C u t 3, volumk, ml. 1 0 4 - found, mmolea Total periodate found, mmoles Recovery, %
EXPERIMENTAL
Resin. The resin used in this work was Amberlite IRX-400, obtained from Resinous Products and Chemical Co. The chloride form was soaked overnight in water and slurried into a large column. The resin was converted to the acetate form by passing sodium acetate solution ( 2 M ) over the resin until the effluent gave no test for chloride ion. This was followed by a distilled water wash to remove the excess sodium acetate. The resin was removed from the column and stored for use in the experiments, The air-dried resin showed a loss of weight of 14y0 on drying overnight a t TO' C. Column. Two sizes of columns were used. The smaller ones were const,ructed from borosilicate glass tubing mm. in outside diameter and about 20 cm. long. To the upper end of the tube was sealed a 6-cm. length of tubing 16 mm. in outside diameter. The narrow portion of the column had a small constriction near the bottom. The resin was held in place by a glass bead seated loosely on the constriction. The larger column was 25 mm. in inside diameter and 20 cm. long, and the resin was supported on a coarse porous glass plate sealed into the tube. Both Columns had a stopcock a t the bottom to control the flow of liquid. The columns were provided with funnels a t the top into which the solutions could be oured. These funnels also served as a part of a continuous $ow setup in which a l-liter separatory funnel served as a reservoir (IO). Procedure. The appropriate amount of the resin in the acetate form was soaked in water and slurried into the column. This amounted to 1.6 grams of air-dried resin for the small columns and 13.4 grams for the large columns. In each case, s, resin bed approximately 10 em. in length resulted. The bed was then washed with several column volumes of water. When the column was to be used for the analysis of a reaction mixture in an organic solvent, it was then washed with the solvent to prevent the precipitation of any reaction products, Washing with the organic solvent was accompanied by a considerable shrinkage of
Recovery of Periodate from IRA-400
Form of resin. Acetate Eluent. 5% KOH
Flow Rate. 2 ml./min. for runs A B and C (small column). 5 ml./min: for runs D, E, and F (large column) A B C D E F ,053
o,913
1,098
51 0.997 50 0.036 50
50 0.862
100 1.091 100
0.005
0.043 50 0.004
1.038 98.6
0.909 99.6
50
23,56
19,05
19,05
155 19.03 315 0.002 4.23
490 18.83
.. . .,.
... , ..
403 18.73 106 0.10
.. . . .,
... ... ... ...
1.093 99.5
23.26 98.7
18.83 98.9
18.83 98.9
RESULTS
Quantitative Recovery of Periodate. .4 number of experiments were performed in which a known amount of periodate ion was adsorbed from aqueous solution on the resin column and then removed with various eluents. The initial experiments utilized the chloride form of the resin and were unsuccessful because of the loss of 5 to 8% of the periodate. This loss can be accounted for quantitatively by assuming that the periodate is reduced to iodate by some substance in the system. It is b e lieved that the chloride ion is responsible for this reduction of periodate, for in one experiment when a high concentration of chloride ion was present, a gas was formed in the resin bed. This gas had the odor of chlorine and gave a positive test with moist starch-iodide paper. This suggested that quantitative recovery of the periodate might be achieved if the resin were converted to a form which is not oxidized by periodate. The acetate form was decided upon, and its use led to recoveries of 99.0 &0.6% of the added periodate. This is indicated by the data recorded in Table 1. Capacity Of The break-through capacity Of the resin was determined by passing standard periodate solution (0.729Jf) through the column until the periodate appeared in the effluent.
751
752
ANALYTICAL CHEMISTRY out without putting the reaction mixture through the column. All reactions were carried out in aqueous solution except that of benzoin where the solvent was a 9 t o 1 by volume mixture of ethyl alcohol and ethyl acetate. This solvent has been recommended by Killard and Boyle (18) for periodate oxidations.
$ o ol
RUNS O S FLAVONOL AND QUERCETIN
The consumption of periodate by flavonol and quercetin was measured using the ion exchange method. The results of these experiments are reported in Table 111. DISCUSSION
VOLUME OF EFFLUENT ( M U
Figure 1. Elution of Periodate from IRA-400 Eluent, 5 % KOH Flow rate, 2 ml. per m i n u t e
Flavonol. Flavonol, melting point 169' C., was prepared according to the directions given by Reichel and Steudel (f5). The compound was dissolved in 25 ml. (80 ml. for run C) of the ethyl alcohol-ethyl acetate solvent described above. The periodic acid FTas added and the misture was allowed to react a t room temperature for the length of time indicated. Khen the reaction mixture was passed through the column, the organic reaction products appeared in the washings. A light yellow crystalline solid, melting point 171' to 174" C., was obtained on evaporation of the solvent. The characterization of this material will be described elsewhere ( f 7 ) . While the action of periodic acid on flavonol produced a colored solution, the solution, if diluted sufficiently, could be titrated directly TTithout use of the ion exchange method. The results of such a titration is reported as run D in Table 111. Quercetin. Quercetin, prepared from rutin by the method of Krewson and Couch ( 6 ) and having a melting point of 313' to 315" C., was also oxidized a t room temperature in 25 mI. of the ethyl alcohol-ethyl acetate solvent. A deep red color rapidly developed in the solution. Within 5 minutes this had changed to a dark yellow. The results clearly indicate a rapid consump-
The small columns containing the usual amount of 1.6 grams of air-dried resin were used for these euperiments. It was found ~ of 2 ml. per minute, 2.32 millimoles of periodate that, a t a f l o rate were adsorbed before break through, while at a flow rate of 1 ml. per minute, 2.98 millimoles were adsorbed. The flow rate used in the adsorption of the periodate from reaction mixtures was 1 ml. per minute. It can be seen that the amount of periodate used in any of the rune did not approach the capacity of the resin. Elution of Periodate. I t was desirable to know the rate a t which the periodate is removed from the resin by 5 % potassium hydroxide solution. This was determined by adsorbing 0.726 millimole of periodate on a small column of resin under the usual conditions and eluting with 5 % potassium hydroxide. Nunierous small fractions of the Table 11. Consumption of Periodate column effluent !$-ere taken and 3Ioles H I L analyzed. An elution curve is Moles Compound perlodate Periodate Consumed __ ahown in Figure 1. The perioWithTheoret Added. With Without ' With 0u.t -Sample Tsed date is removed very rapidlv, resin resin hlmoles resin resin Compound irg M ~ O I & over 90% coming off in the 0.99 0.613 0.723 ... ... 0 619 Ethylene glycolo 38 4 0.439 1 00 0.729 ... 0 440 27 3 first 30 ml. and 98% in 58 ml. , . . 0.729 0:597 1.01 0 593 36 8 Total recovery in this esperi... . . 0.729 0,545 1.02 33 2 0 535 ment was 99.3%. I 137 1,283 2.03 0 632 ... ... Diethanolamine b 66 5 1.98 1.078 0,909 0 461 ... 48 4 Runs on Compounds of 1.078 ... ... 0:874 1 92 47 9 0 456 1 . 0 7 8 . . . ... 0 . 8 6 4 0 442 46 4 1 . 9 5 Known B e h a v i o r t o w a r d 0,723 0.427 4 99 0 0857 ... ... SorbitolC 15 6 Periodate. I n order to ensure 0.729 0,437 4.91 16 I 0 0884 ... 0.729 .., .. 14 2 0 0779 0:407 5.22 that the column procedure did 0.729 ... 5.18 16 2 0 0889 0 460 not interfere with the stoichio0 729 0 . 5 3 6 5 01 0 107 ... ... 21 2 Glucosed metrical relationships between 0.729 0.551 0 110 5 01 ... . . 21 8 5.02 0.729 0.542 21 4 0 108 the periodate and a reactive ... ... 0 113 0.729 0 : 6k7 4.94 26 4 0.729 ... ... 0 103 0.516 5.01 20 5 organic substance, six com0.729 0 . 4 2 6 2 .06 0 206 . . . , . . llethyl-D-gluco40 1 pounds whose reactions with 0.729 0 501 2.03 pyranosidee 47 9 0 247 ... ... 0.729 ... 0 224 0 :468 2.08 43 6 periodate have been previously 0.729 .. 0 220 ... 2.07 42 8 0.456 investigated were selected for 1.078 . . 0 808 ... 0.99 171.2 0.800 Benzoin/ 1.078 . . 1.01 0 606 0 610 ... study. The products from the 128.4 . . 7.60 6.74 1 .oo 6 77 14350 oxidation of all of these sub0.98 25.9 15.4 ... 33580 15 84 ... stances are colorless, so that a Redistilled, center cut, b.p. 197O. Total volume of solution 10 ml., reaction time, 12 hr. a t room temp. 6 Matheson. Total volume of solution, 10 ml., reaction time: 2.5 hr. on steam bath. analyses could be performed Matheson, m.p. 163-5O. Total volume of solution, 10 ml. reaction time, 12 hr. a t room temp. d Baker C.P. Column runs and first control, total volume of'solution, 10 ml.. reaction time, 14 hr. a t room temp. both with and without use of Second and third controls carried o u t in 20 ml. of a periodate solution which was 0.05M in sodium bicarbonate as t h e r e s i n . T h e r e s u l t s of recommended by Reeves (f4),reaction time, 1.25 hr. a t room temp. e Prepared from glucose. m.p. 166O. Total volume of solution, 10 ml.. reaction time, 14 hr. a t room temp. these experiments are reported f Eastman Kodak practical recrystallized from ethyl alcohol m.p. 1 3 4 O . Small column runs: sample dissolved in 25 ml. ethyl alcohol-ethyl acetate mixture, 10 ml. of aqueou; periodic acid added, reaction time, 24 hr. a t room i n Table 11. I n all casee, the temp. Large column runs: 80 ml. ethyl alcohol-ethyl acetate mixture, 10 ml. aqueous periodic acid, reaction time. 17 hr. a t room temp. Control: 50 ml. ethyl alcohol-ethyl acetate mixture. 25 ml. aqueous periodic acid, reaction results obtained with the resin time, 36 h r . a t room temp. checked closely with the simulQ Large column runs. taneous experiments carried
753
V O L U M E 26, NO. 4, A P R I L 1 9 5 4 Table 111. Periodate Oxidation of Flavonol and Quercetin
Compound Flaronol
Quercetin a
Run A B C D
Sample Used hIg. hlmoles 121.0 0.508 139.3 0.586 678.sa 2.83 112.2 0.473
A 43.0 B 41.6 Large column run.
0.142
0.138
Periodate hlmoles Reaction 3lmoles conTme, Hr. added sumed 0.723 0.531 69 0.723 0.558 45 7.60 2.73 17 0 . 7 2 3 0.474 69 0.718 0.718
0,306 0.301
0.25 0.50
Ratio, Moles HIOc Moles Compound 1.04 0.95 0.96 1. 0 0 2.15 2.20
tion of 2 moles of periodate. In an experiment which ran for 94 hours, over 3.5 moles of periodate were consumed. A more detailed study of this slower oxidation and an examination of the highly colored reaction products are now in progress, LITERATURE CITED
(1) Clutterbuck, P. W,,and Reuter, F., J . Chem. Soc., 1935, 1467.
(2) Fleury, P., and Lange, J., J . pharm. chim., (8) 17, 409 (1933). (3) Herissey, H., Fleury, P., and Joly, LI.,Ihid., 20, 149 (1934). (4) Jackson, E. L., “Organic Reactions,” Vol. 11, Roger Adams, Ed., pp. 341-75, Sew York, John U‘iley & Sons, 1944. (5) Jackson, E. L., and Hudson, C . S., J . A m . Chem. Soc., 58, 378 (1936); 59, 994 (1937). (6) Krewson, C. F., and Couch, J. F., Ibid., 70,257 (1948). (7) Linstedt. G., Sature. 156, 488 (1945). (8) llalaprade, L., Bull. SOC. chim.,(4) 43, 683 (1928). (9) Nalaprade, L., Compt. rend., 186, 382 (1928). (10) Morton, A. A . , “Laboratory Technique in Organic Chemistry,” p. 174, New York, AIcGraw-Hill Book Co., 1938. (11) Xicolet, B. H., and Shinn, L. A . , J . A m . Chem. Soc., 61, 1615 (1939). (12) Rappaport, F., and Reifer, I., Mikrochim. Acta, 2, 273 (1937). (13) Rappaport, F., Reifer, I., and Weinmann, H., Ibid., 1, 290 (1937). Re‘eves, R. E., J . A m . Chem. SOC.,63, 1476 (1941). Reichcl, L., and Steudel, J., Ann., 553, 83 (1942). Smith, G. F., “dnalytical Applications of Periodic Acid and Iodic Acid,” 5th ed., Columbus, Ohio, G . Frederick Smith Publishing Co., 1950. (17) Smith, 11. A , , Gnau, L., and Willeford, B. R . , forthcoming Dublication. (18) Willard, H. H., and Boyle, -A. J., ISD.Esc. CHEM.,A h . k ~ ED., . 13, 137 (1941). RECEIVEDf o r review Xovember 23, 1953.
Accepted December 28, 1953.
Determination of Boron in Boron-Carbon Film Resistors IRVING G. YOUNG Research Division, International Resistance Co., Philadelphia 8, Pa.
P
YROLTTIC carbon film resistors are prepared by “cracking” of hydrocarbon gases in a closed chamber and deposition of carbon on suitable ceramic bodies. The nature and properties of the films obtained depend on the reaction conditions as well as the ceramic surface. Recently, it has been found that addition of boron compounds to the reaction mixture produces films with new and interesting properties ( 3 ) . It xas, therefore, of great interest to determine the amount of boron in these films, and correlate this with film properties, The titration of boric acid with alkali in the presence of mannitol has long been used to determine boron (4). Wilcox ( 6 ) titrated 250 to 5500 y of boron with a precision of 5 to 10% while with known quantities in this range he obtained recoveries of 100 z!z 301,. Foote ( 2 ) obtained recoveries of 100 & 1% when titrating known amounts of boron in the range 500 to 10,000 y . The experience of these workers as well as others (5) was useful in developing a procedure suitable for the determination of boron in the coatings of boron-carbon ceramic resistors.
Iiimble Resistant glass flask with standard-taper joint. Add 3 ml. of concentrated sulfuric acid, or enough to wet and cover the ceramic bodies, and 5 to 10 drops of concentrated nitric acid. Assemble the flask with a reflux water-cooled condenser and heat the flask gently with a small flame or a Glas-Col heater. Five minutes will usually suffice to dissolve the film completely; more nitric acid may be added dropwise through the top of the condenser, if necessary. Allow to cool, dilute carefully with water, and transfer quantitatively to a 100-ml. beaker. If the volume is more than 50 to 60 ml., evaporate to this volume, by placing in an oven at 125” C.
APPARATUS
Table IT. Determination of Boron in Coating of Ceramic Resistors
Beckman Model G pH meter. Kimble microburet, platinum alloy tip, 5-ml. capacity, 0.01ml. subdivisions. Magnetic stirrer. Kimble Resistant glass beakers and flasks. REAGENTS
Sulfuric and nitric acids, concentrated, C.P. Saturated sodium hydroxide, prepared in “boron-free” flask. Sodium hydroxide, 0.015alr, carbonate-free. Mannitol, C.P. Methyl red indicator solution, 0.1%. Standard boric acid solution. Dissolve 0.5715 gram of C.P. boric acid in water and dilute to 1 liter; 1 ml. == 100 y of boron. PROCEDURE
Weigh a number of clean, dry ceramic resistors containing a total of 200 to 500 y of boron in the film. Place in a 150-ml.
Table I. B,
y
100 199 299 399 199 199
Titration of Know-n Amounts of Boron SaOH, M I 0.61 1.17 1.68 2.25 1.11 1.18
y/M.
164 170 178 178 179 168 A x - . = 173; 0 = 5 . 8
(All weights in micrograms) Total B Titrated B in Coating, ‘% Weight of Coating 3080 286 9.3 638 3140 % I O 267 3160 8.5 306 3020 10.1 Av. 9 . 3 ; D = 0.6 B5O 2170 209 8.5 2410 676 8.90 1970 196 9.9 3410 302 8.9 h v . 9.1; D = 0.5 ClOO 1250 145 11.6 1400 150 10.7 Av. 11.2 D4OO 790 48 6.1 640 40 6.2 Av. 6 .2 a Corrected f o r NBS borax added to sample.
Sample A18
