1226
ANALYTICAL
CHEMISTRY
warmed to 20' C. one should wait 8 to 10 minutes but not longer than 15 minutes to compare or measure the color formed.
sample for testing for chlorine dioxide with the tyrosine reagent. The chlorine plus manganese either in natural water or in a bicarbonate solution gives no color with the tyrosine reagent. The chlorine dioxide oxidizes the manganous ions in the bicarbonate solution of natural water instantly, causing a dark brolvn color to form; when tyrosine reagent is added to the manganic solution or suspension after treatment with chlorine dioxide, no tyrosinechlorine dioxide color develops. The data of Figure 6 were obtained a t room temperature or about 25" C. When the temperature of the chlorine diolide solution was lowered to 4' C., 80 minutes were required to obtain the maximum color intensity.
CONCLUSIONS Tyrosine is selective for chlorine diouide, producing a color with which there is no interference from hypochlorous acid, chloramines, and manganese. The method for the determination of chlorine dioxide is simple and rapid. The reproducibility is adequate for higher concentrations. The sensitivity is poor for the chlorine dioxide Concentrations less than 0.2 p.p.m. sometimes used in water treatment. LITERATURE CITED Aloy, XI. A1 , and Rabault, C., Bull. soc. chzm. Paris, Ser. 4,
RECOMMENDATIONS
111,391 (1908). Am. Public Health Assoc., Xew York, "Standard AIethodn for the Examination of Water and Sewage," 9th ed., 1946. Aston, R. N., J . A m . Wuter Works Assoc , 42, 151 (1950). Rerge, XI. A., MBm. sot. ing. civzls France, V 1900, Part I, B 475. Haller, J. F., and Listek. S. C., AXLL.CHEM.,20, 639 (1949). Harlock, C. R., Water & Sewage Works, 100, 74 (1953). Ingols. R. S., J . Inst. Water Engrs., 4, 581 (1950). Ingols, R. S.,Wyckoff, H. A., Kethley, T. .I.,Hodgden, H. W., Fincher, E., Hildebrand, J. C., and Mandel, J. E., Ind. Eng. Chem., 45,998 (1953). Marks, H. D., Williams, D. B., and Glasgow, G. G., J . Am. Wuter Works Assoc., 43, 201 (1951). Palin, A4.T., J . Inst. Water Engrs., 3, 100 (1949). RECEIVED for review September 17, 19.53. Accepted March 18, 1954.
I t is recommended that 2 ml. of reagent be used per 100-ml. sample for concentrations up to 2.5 p.p.m. of chlorine dioxide plus hypochlorous acid and that with higher concentrations, the sample be diluted below 2.5 p.p.m. or proportionately more reagent be used. Permanent cobalt nitrate standards can he prepared for comparison of color produced in the chlorine dioxidetyrosine reaction. I t is recommended that cobalt nitrate standards contain 140 p.p.m. of cobalt nitrate for every 0.1 p.p,m. of chlorine dioxide. Because in the chlorine dioxide-tyrosine reaction the maximum amount of color is produced to 6 in 8 minutes at 20" C. Ivhile beyond 15 minutes the color begins to fade, after the solution is
Investigations supported in part by a research grant from the National Institutes of Health.
Detection of Bismuth by Dithizone in Molten Naphthalene JACK K. CARLTON and WALTER C. BRADBURY Institute o f Science and Technology, University o f Arkansas, Fayetteville, Ark.
T
HE organic reagent, dithizone (diphenylthiocarbazone), is well known for itR use in the detection and determination of certain metal ions (2). The reagent is commonly employed in a chloroform or carbon tetrachloride solution and is used as an extraction medium for the desired metal ions. I n applying the reagent, selectivity is attained by masking the interfering ions with appropriate complexing agents, by the careful adjustment of pH, or by a combination of these methods. I n certain cases double extractions have proved advantageous; the metal ions are extracted into the dithizone-chloroform medium and the organic phase is then extracted by an aqueous solution the pH of which has been adjusted to favor the solubility of the desired metal dithizonate. Feigl and Baumfeld ( 1 ) found that several metsls foinied colored complexes in molten 8-quinolinol and have suggested this as a method of detection for several of them. West and Granatelli (3)studied the reaction of metal salts with molten 8-quinolinol microscopically and have established that the characteristic crystals formed by a number of cations and anions offer an extremely sensitive method of detecting them. During an investigation of various reactions in nonaqueous media the authors found that a solution of dithiaone in molten naphthalene reacted v-ith bismuth salts very rapidly to yield a brilliant red color. Bismuth concentrations in the range of 0.004 y are easily detectable. Reactions of the dithizone-naphthalene reagent with other metal ions and the nature of interferences and their masking were studied. REAGENTS Dithizone, Matheson Co., a 0.025% solution in Baker's naphthalene.
6.p.
Bismuth chloride, J. T. Baker Chemical Co., prepared in 1 . O J I hydrochloric acid to contain 1007 per drop. Dilutions were made from this stock solution. Reagent grade chemicals were used in the interference studies and nere made up to contain 5007 per drop and were used in this concentration. acid was added where needed to retain hydrolyzable ions in solution. EXPERIMENTAL Because of the intense color of dithizone, maximum sensitivity could not he obtained using this reagent undiluted in the molten state. In addition, its melting point is relatively high and its stability is lowered at higher temperatures. Consequently, naphthalene ivas selected as an inert, low melting solvent for the reagent. The reagent solution was prepared by dissolving 16 nig. of dithizone in 75 ml. of chloroform, mixing with 66 grams of naphthalene, and finally evaporating the chloroform from the mixture. Dilutions of the stock bismuth chloride solution were made to establish the limit of identification of this ion. One drop of the test solution was evaporated on a spot plate previously heated to about 90" C. and a few milligrams of the reagent were added. The red color of the bismuth dithizonate was clearly disrerned a t a concentration of 0.0047 of bismuth. Limits of identification of other metal ions Rere determined following the same procedure. Observations of the reactions between various cations and the reagent are listed in Table I. RIany of these gave salts analogous to those obtained employing the chloroform solution of dithizone, while others vary considerably. In some cases the color changes required long periods of time and relatively large concentrations of the metal ion. Cadmium, tin, mercury, zinc. and silver gave almost instantaneous reactions.
1227
V O L U M E 26, NO. 7, J U L Y 1 9 5 4 An interference study was made employing concentrations of diverse ions 100 times that of bismuth. Oxalate and phosphate prevented the normal response of bismuth to the reagent and cadmium, zinc, mercury, silver, and tin interfered by color masking of the bismuth-dithizone reaction. Attempts to sequester interferences through the use of conventional masking agents such as cyanide, thiocyanate, fluoride, and chloride met with some success. Cyanide ion and chloride ion effectively masked the interferences of mercury and silver, respectively, without an appreciable reduction in the sensitivity of the test.
Table I .
Cation
-
IIg S Zn T - -' T '
co*Sb++31n'ce+-+"go+- +
+: ;
+ Fe++Ph++ Cd++
Reactions of Dithizone-Naphthalene Solution with Various Cations Color Developed Yellow-orange Dull red Pink Red Orange-red Pale pink Red-brown I'eiiolv-orange Yellow-brown Brown-violet Orange-red Dull red Red
Time Required, Seconds
< 10 < 10 < 10
Color of Dithiaonate in Chloroform Yellow-orange Purple-red
....
> 80
Violet
> 60 >eo < 10
Vio1et:b;own None Yellow None Violet
60 >60 > 60 > 60
Red Red
< 10
....
the bright red coloration does not develop in 10 seconds, a negative test for bismuth should be reported. If mercury is known to be present, the dry sample may be taken up in a small quantity of water and a few milligrams of sodium cyanide added to the solution, before evaporation, in order to obtain intimate mixing and to prevent the interference of that ion. If silver is present, sodium chloride may be utilized similarly. REMARKS
The reagent as used in the manner suggested here offers a very sensitive means of detecting bismuth, definitely more sensitive than the chloroform-dithizone extraction procedure. During the study of the reactions of molten 8-quinolinol with metal salts Feigl and Baumfeld ( 1 ) also noted greater sensitivity than when the reagent was employed in an aqueous reaction. It is pointed out in Table I that several cations react with the reagent, some of them quickly and with the formation of strong colors. Among these the most sensitive are: cadmium, 0.027; mercury, 0.017; tin, 0.004-y; and silver, 0.027. Where these ions are known not to exist in cornhination, or n-here separations' can conveniently be made, the dithixone-naphthalene reagent may be useful in their detection. ACKNOWLEDGiMENT
This research was supported i n xhole or in part by The United States Air Force under contract number AF lS(600)-960, maintained by the Ofice of Scientific Research, Air Research and Development Command. The authors wish to express their appreciation for this support.
REC0311lEhDED TEST PROCEDURE
Iiito the depression of a white spot plate which has been previously heated to about 90" C. on a hot plate, a small amount of the solid sample is dusted (if the sample is in solution, a drop of the test solution is added and evaporated) and a few crystals of the dithizone-naphthalene mixture are added. I n the presence of bismuth the melt turns a brilliant red immediately: if
LITERATURE CITED
(1) Feigl, F., and Baumfeld, L., Anal. Chim. Acta, 3, 15 (1949). (2) Fischer, H., 2. angew. Chem., 42, 1025 (1929). (3) West, P. W., and Granatelli, L., -4~~1.. CHEW,24, 870 (1962).
RECEIT-ED for review Sovember 27, 1953. Accepted April 8, 1951.
Determination of Fumaric, Malic, and Succinic Acids in Fermentation Broths NIKOLAJ LEMJAKOV Piedmont College, Demorest,
Ga.
Editor's Note: Professor Lenijakov Fas in the laboratories of Heinrich Knobloch, Institute of Technology in Prague, during 1943-45, as head of a research group. Results of his work on fumaric acid fermentation mere to he the basis of his doctoral dissertation,
but he was forced to leave Czechoslovakia before the thesis could be completed. What is published here is a brief summary of a portion of Lemjakov's work, reconstructed from memory.
S
T.41JDARD European methods for the determination of acids i n fumaric acid fermentation samples are inconvenient. For example, the quantitative determination of fumaric acid usually necessitates an initial 3-day extraction with ether, folloxed by application of the mercurous fumarate method. As i t was not feasible to use such elaborate and lengthy proceduies for large scale tests, attempts were made to simplify the annlytical process. I t was found possible to obtain reliable analytical results for fumaric acid by applying the mercurous fumarate method directly to the fermented substrate without extraction. The differences in the results of the analysis of samples of a substrate and of other samples of the same substrate to which \?ere added liriown quantities of fumaric acid corresponded to the amounts
of added fumaric acid. Large scale practical application of this technique Tms satisfactory. The results were further checked by polarographic determination of the fumaric acid; concordant results were obtained by both methods. The polarographic method appears to be the more accurate as well as the more rapid method, and requires less sample. The mercurous nitrate method requires 10 ml., whereas 2 ml. are sufficient for the polarographic method. Preliminary experiments showed fumaric acid to be destroyed quickly by permanganate in cold acid solution, but malic and sucrinic acids were not. Malic acid is often present in a fumaric acid fermentrtion. Recalling the titration of oxalic acid with permanganate and the building of catalytically active intermediary products, the author conducted an experiment with a mixture of fumaric and malic acids; complete oxidation of both acids occurred. On the basis of these observations a new method for the determination of succinic acid TVBS devised, which eliminated the extraction necessary in the usual methods. SUCCINIC ACID DETERMINATION
Transfer 10 ml. of fermented substrate to a porcelain dish. Add 2 Inl. (or an excess) of concentrated nitric acid (nitric acid is
