thus checks its coprecipitation. Though separation from Ce(IS’), which forms a light yellow precipitate v i t h the reagent, was not possible, separation could be effected by reducing Ce(IV) to Ce(II1) with sufficient quantity of hydrogen peroxide and removing the excess of latter by boiling. Procedure for Palladium(I1). A solution of palladium chloride containing 10 t o 50 mg. of metal was diluted to 100 t o 150 ml. in a borosilicate glass beaker, and the p H was adjusted betn-een 0.2 to 0.8 by the addition of 3 to 7 ml. of analytical grade concentrated hydrochloric acid (sp. gr. 118) To this solution, IThich may contain varying quantities of diverse ions, an excess of 2% n-./v. alcoholic solution of the reagent was added from a buret with constant stirring. Fifty t o 60 mg. of the reagent, corresponding t o about 125% excess, was employed for every 10 mg. of the metal. Larger excess of the reagent was tolerated. The precipitated coniplex was digested with occasional stirring on a steam bath for 15 minutes to facilitate the coagulation of the precipitate and its subsequent filtration. After cooling t o room temperature (about 2 t o 3 hours) the precipitate was filtered on a weighed G-4 sintered-glass crucible, washed first with about 25 ml. of cold 1% v./v. hydrochloric acid, subsequently washed with 7 5 to 100 ml. of cold mater, dried a t 110’ C. for an hour, and weighed. The weight of the precipitate multiplied by 0.2470 gave the weight of palladium. Cu(I), Pb(II), Hg(I), and Tl(I), which form partially soluble chlorides, interfered with the analysis and were therefore oxidized to higher valency states before the addition of reagent. Direct separations from Pb(11) and TI(1) n-ere possible if the reaction mixture was diluted sufficiently to keep their less soluble chlorides in solu-
tion. I n the separation of palladium from antimony, about 1 gram of tartaric acid and a n additional 5 ml. of concentrated hydrochloric acid were added to the reaction mixture to keep antimony in solution. The precipitate was washed initially n i t h a solution containing 2% v./v. hydrochloric acid and a little tartaric acid. When iron(111) was present, a faint brownish yellow turbidity n as produced in cold which, however, rapidly disappeared during the course of digestion.
estimations have been made so far. Some of the results are given in Table I. ACKNOWLEDGMENT
As the composition of palladium-2thiophene-trans-aldoxime coniplex corresponds to the formula [Pd(C5H50NS)2C12]. nhich is a coordination comple.; analogous to sevrral other complwes of palladium exemplified by dichlorodiamino palladium(I1) [Pd(SH3)2C12],it was anticipated that the estimation of palladium by this method might not he feasible in presence of anions other than chloride. Hom-ever, contrary to this belief, satisfactory result. n-cre obtained in presence of fairly large excesses of other anions like fluoride, acetate, nitrate, sulfate, and tartrate. The other anion complexes are not formed from the strong hydrochloric acid medium because the chloride complex is the more stable and less soluble. From palladium(I1) nitrate and nitric acid solution, and from palladium(I1) sulfate and sulfuric acid solution, the corresponding yellow insoluble complexes could be obtained n ith 2-thiophene-trans-aldoxime but both complexes were found unsuitcd for the determination of palladium by direct neighing on ing to their spontaneous decomposition a t about 100” C. Concerning estimation of palladium as such and also its separation from various divcrse ions, about 260 concordant
The authors are indebted to the Director, National Chemical Laboratory, for permitting S. G. Tandon to work as guest norker and to the Government of hfadhya Pradesh for granting study leave to him. They also thank 1‘. S. Pansare and colleagues for the microanalyses of compounds. LITERATURE CITED
(1) Charlot, G., BBzier, D., “Quantitative Inorganic Analysis,” p. 524, Wiley, Xew York, 1957. (2) Connick, R. E., JIcVey, 11’. H., J . .4m. Chem. Soc. 71, 3182 (1949). (3) Feigl, F., J . Chem. Educ. 20, 298 (1943) \ - - - - I
(4) Gilchrist, R., Bur. Standards J . Research 12, 291 (1931). (5) Hartough, H. W.,“Thiophene and Its Derivatives.” n. 313, Interscience, Ken. Tork, 1052. 1\ 6* ) Haves. J. R.. Chandlee. G. C.. .$SAL. C H E ~ I14. . 49i 11942). ‘ . (7y Hillebrahd, W: F., Lundkll, G,., E. F., Bright, H. A , Hoffman, J. I , hpplied Inorganic Analysis,” 2nd ed., p. 379, Kilev, S e i T York, 1953. (8) Horning, E. C., “Organic Syntheses,“ Collective 1-01,3. 11. 590. Wile\.. ?;ex Tork, 1955. (9) Huffman, E. H., Beaufait, L. J., J . A I ~ Chem. L Soc. 71, 3179 (1949). (10) Sfhreiber, R. S., “Organic Syntheses. Vo1. 31, D. 108, Wiley, Sew York 1951. (11) Sogani, X.C., Bhattacharya, S. C., AKAL.CHEM.28, 81 (1956). (12) T-oter, R. C., Banks, C. V., Diehl, Harvev. Ibid., 20, 652 (1948). (13) Kezt, P. IT., J . Chem. Educ. 18, 528 (1941). /
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RECEIVED for review January 26, 1959. Sccepted Sovember 12, 1959.
Rapid Test for Identification of the Isomers of Phenylenediamine R. G. FRIESER’ and P. A. SCARDAVILLE’ Central Research laboratories, lnterchemical Corp., 4 3 2 West 45th St., New York 36, ,A new specific one-reagent method for the qualitative identification of 0 - , m-, and p-phenylenediamine is described. The test has been modified for quantitative determination.
A
of the literature did not reveal a simple one-reagent method of differentiating the three isomeric phenylenediamines. Available methods are based on coupling reactions and the production of organic pigments (8) or SURVEY
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azo dyes (6). The drawbacks of these methods are that the reagent solutions must be freshly prepared and several steps are required. Furthermore, each of these methods only gives positive identification of a single i,qomer. Some methods (4, 9) permit differentiation from other amines; a titrimetric method (Z), recently published, is timeconsuming and must be carried out in an inert atmosphere. Still other methods ( 3 , 7 , 10) have been used but are not sufficiently specific. Procedures exist
N. Y. by which the three isomeric phenylenediamines can be differentiated (I, 5 , 1 2 ) but are cumbersome because they use a complicated scheme of a variety of organic and inorganic reagents. These methods do not readily lend 1 Present address, Radio Corp. of America, Semiconductor and Vaterials Division, Somerville, N. J. 2 Present address, Radiation Application Inc., 42-30 24th St., Long Island City, 3 . P.
themselves for use as a rapid test in the laboratoij , and certainly not as a spot test. -4 11 ell-known quantitative test for ~,lienylenetlianiine (11) is the development of the blue color of the reduced phosphotungstic acid in solution buffcred to a pH of 8. The color intcJnsit>-tlim is read a t 650 nip. This t w t . lion ever, does not differentiate betwcon tlic. 01 tho, ineta, and para isomers. ed that, if the solution is not buffcrrtl a n d phosphomolybdic acid is used, it is not reduwd; a complex is forrne(l, the color of which dcpendq on thc rcllntiw po-itions of the nniine groups on tlic bcnzonr ring. This then is a siniplc n a y to diffcrentiqtc the three isomers.
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Table 1.
Limits of Identification of Phenylenediamines in Test Tube Solutions Lower Limits of Total Isomer Color Reagent,a MI. Amine Concn., '11 Yolume, MI. Ortho Red-brown ppt. 1 10-4 10 (colloidal) 3 . 4 x 10-4 15 hIeta Pale green soln. * 5 10-4 10 Para Blue-green soln. 1 (immediate) a 25% w./v. phosphomolybdic acid. Color hard to see a t first, but appears clearly R-ithin 90 minutes, particularly against a water blank. Table II.
Color Specificity of Phenylenediamines and Limits of Identification of Spot Test
Amine o-Phenylenediamine
EXPERIMENTAL
Preparation of Reagents. PHOSPHOMOLYBDIC ACID ( E a s t m a n Kodak Co.) )vas used without recrystallization. Fifteen grams of phosphomolybdic acid were dissolved in 90 nil. of distilled water. ~ I K E SOLCTIOXS: Aqueous solutions were prepared a t concentrations of 10-l to 10M4Vof the following amines: o-phenylenediamine (Matheson, Coleman & Bel[ Division of the Matheson Co., Inc.) melting point 1012" C., literature 102W3 C.; p-phenylenediamine (;iinerican Cyanamid), melting point 143-5' C., literature 140-7" C.: and m-phenylenediamine ($ntara Chemicals, General Aniline &- Film Corp.), nielting point, 60-1" C., literature G1-4" C.
m-Phenylenediamine p-Phenylenediamine
Spot Plate Test Wet Paper Red-brown Purple ring PPt. Grey ppt. KOcolor Blue-green ppt. Green
PROCEDURE
Dried Paper Purple ring
Sensitivity of Spot Plate Test 10-4
Grey Green to bluegreen Blue Bniline ... Blue Red front,a blu e Red front,a blue 2,4-Diaminophenol ... body body o-bminophenol Light brown Light brown m-Toluidine ... KOreaction n'o reaction a The advancing outer edge of the amine solution as it n-ets the paper.
a few drops of the amine solution along side so that the two solutions diffuse into each other. The color specific for the amine present is developed where the two solutions intermix. RESULTS
The results are summarized in Tables
I and 11. Each diamine gives a disThe test can be carried out in test tubes, on a spot plate, or on filter paper previously saturated with phosphomolybdic acid solution. Test T u b e Procedure. Place 5 ml. of an amine solution of t h e above molarities into a test tube and 1 drop of t h e phosphomolybdic acid solution. A water blank should be run simultaneoiisly as a control. T h e colors obtained were observed over a period of 2 hours. Spot Plate Test. Place 5 drops of t h e amine solution in a depression on t h e spot plate. -4dd 1 drop of t h e phosphomolybdic acid solution. T h e identifying color develops irnmediatcly and is stable for hours. Spot Paper Test. Saturate K h a t man si50 filter paper n i t h 25% (.-. /v.) phosphomolyhclic acid solution. P u t a fen drops of t h e "unknown" amine solution on the treated paper either immediately after preparation of the test paper or after having dried the test paper previouslj, in a draft oven a t about SO" t o SO" C. It will then become greenish in color and stable for 1 year if kept in the dark. For a n alternate procedure, put a fendrops of the phosphoniolybdic acid solution on the filter paper and then place
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tinctly different colored precipitate \vliich is stable for several hours. If the test is carried out on filter paper, a colored spot is obtained. K i t h some practice, even a mixture of tu-o of the amines can be identified. On the othpr hand, when the amine solutions are alkalinized n i t h 1 drop of a lOYc sodium carbonate solution per 5 drops of reagent solution, all three diamines give blue solutions. It is therefore possible to test the unknown first to determine n hich amine is present and then repeat the test on a n alkalinized portion of the solution to determine quantitatively the amount of diamine present by measuring the density of the blue color of the solution. Substituting phoqphotungstic acid for phosphomolybdic acid gives no visible reaction at all when used according to the procedure recommended above for phosphomolybdic acid, in neutral or acid media. Other amines which were investigated did not give an!- colors n hich n-ould interfere when the dried paper was used. DISCUSSION
The above test is a simple. rapid
10-2 10-3
... ... ... ...
method to differentiate aniong the three isomers of phenylencdiainine. Further~ i i o r (the ~ ~ reagent is useful as a spot reagent after a mixture of the phenylenediamines has been separated by paper chromatographic tcchniques. As the phosphomolybdic acid is only reduced by diamines a t alkaline pH's, a t neutral pH complexes are presumably formed. Because, in this cas(', the type of coniplex fornied depends on the position of the amines, it is reajonable to expect a different coniples for each isomer; the fact that the color too differs is fortuitous, but fortunate. LITERATURE CITED
(1) Bertetti, Jolanda, -4nn. chim. (Rome) 44,313-20 (1954). (2) Cihalik, Jaroslav, S'arejnova, Drakomir, Chem. listy 49, 1167 (1955). (3) Cumming, ST. PIT., J . Chem. SOC.125, 2541-2 (1924). (4) De Paolini. I.. Gazz. chiin. ital. 60. S59-a (193oj. ' (5) Kulberg, L. M.,Ivanova, Z. I-., Zhztr. Anal. Khim. 2, 198-209 (1947). (6) Langecker, Hedn-ig, Biochem. Z. 324, 214-16 (1953). ( 7 ) Lellmann, Ann. 228, 201, 249 (1885). (8) ?\lever, R., AIaier, J., Ibid., 327, 28 (1903). (9j Ruziczka, Walther, 2. anal. Chem. 80,185-90 (1930). (10) Scheiner, E., Biochenz. Z . 205, 252 ( 1929). (11) Snell, F. D., Snell, C. T., "Colorimetric Method of Analysis," 3rd Ed., Vo1. 11, p. 227, Van Sostrand, Kew Tork, 1949. (12) Welcher. F. J.. Proc. Indiana dcad. ' Sci. 63, 110-12 (1953). RECEIVEDfor review July 14, 1959. Accepted November 13, 1959. ~
VOL. 32, NO. 2, FEBRUARY 1960
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