The solutions in the flasks were then diluted to 100 ml. with additional carbon tetrachloride and the absorbance measured a t 530 nip. A blank consisting of all reagents, a i t h the exception of the zinca-oil \elution, was carried through the procedure and used as the reference during absorption measurements. RESULTS A N D DISCUSSION
Table I. Determination of Zinc in Oil Solution of Paranox 15
Sample wt., grams 0.0451
0.0827 0.1390 0.2133
Absorbance 0.118 0.210
0.370 0.530
Zinc, yo 0,015 0.015 0.015 0.015
additive concentration in a given system without knowing the actual zinc content of the additive. Interferences. Dithieone forms colored complexes with many elements which could possibly be present in used oils; therefore, this method is limited to the analysis of new oils containing only zinc type additives. ACKNOWLEDGMENT
When the absorbance was plotted againht zinc roncentration, a linear relationship was observed. Precision and Accuracy. T h e least squares line was calculated from the standard curve d a t a a n d is given by the following equation: absorbance = 0.017 (pg. of zinc) 0.004. This equation was used to predict the zinc value for each point on the standard curve. The predicted valueq were then compared to the known values; standard deviation was i 0.8. The standard curve covered the range of 6.0 to 80.0 pg. of zinc
+
Commercial Additives. A solution of a commercially available zinc dialkyl dithiophosphate type additive (Paranox 15, Enjay Chemical Co.) in lubricating oil was prepared a n d analyzed for zinc content using this method. T h e results are given in Table I. When the weights of the above samples are plotted against the absorbance values for the resulting zinc dithizonate solutions, a straight line relationship is exhibited. By using such a relationship one can follow the
The advice and support of Nicholas Galitzine is gratefully acknowledged. The author also thanks Rose Frazar for helping with the determinations. LITERATURE CITED
( 1 ) Gehardt, P. P., Hartmann, E. R., ANAL.CHEM.2 9 , 1223 (1957). ( 2 ) Sandell, E. B., "Colorimetric Determination of Traces of Metals," 3rd ed., YoL 3 , Interscience, Sew York, 1959. JESSEM .HOWARD I11 RZajor Appliance Laboratorier General Electric Cn. Louisville, Ky.
Detection and Identification of Isomeric Pyridine Monoamidoximes by Paper Chromatography SIR: The separation and identification of pyridine nionoamidoximes by any method has not been reported in the literahre, and as part of a research program on aniidoximes this separation was studied. Several workers have investigated the separation of pyridinecarboxylic acids because of their biological importance (I, 2 , 4 ) , and pyridineamidoximes are relat'ed to these compounds. Kitriles are easily converted to amidoximes by reaction with hydroxylamine (6); therefore the method described can also serve as a means of identification of monocyanopyridines. EXPERIMENTAL
Pyridine-2-, -3-, and -4-amidoxime were synthesized from the corresponding cyanopyridines by reaction with hydroxylamine ( 3 ) . Aqueous stock solutions of the amidoximes were prepared and 5 pg. of each compound, plus a mixture of the three, were spotted on duljlicate Whatman S o . 1 chromatographic paperq. The two chromatograms were develolied for 8 to 10 hours by an ascending technique in a solvent of n-butyl alcohol: glacial acetic acid:water [ 4 . 1 : 2 v./v. ( 4 ) ] . The solvent front moved about 17 cm. in 8 hours a t 25" C. The Chromatograms were air dried. One chromatogram was ql~rayed with a reagent prepared by
mixing equal volumes of methanol and an aqueous solution of the following composition (4) lyOaqueous solution of Fe(l;H4)* (SOI)* 6 H 2 0 (Mohr's salt) : 10% aqueous solution of S H z O H.HClpyridine ( 2 0 : 2 :1 v./v.). The second chromatogram was sprayed with a 1% methanolic solution of 2,4-dinitrofluorobenzene [Sanger's reagent (4, 5 ) ] and heated for 15 minutes at 11G20" C. It was then sprayed with a 5y0aqueous solution of potassium hydroxide and dried at 110-20" C. for 15-20 minutes.
Other work in this laboratory has shown that the compound formed with 2,4dinitrofluorobenzene is the N-(2,4dinitropheny1)pyridineamidoxime derivative. Because the R, values for pyridine-3- and -4-amidoxime are so close under the conditions used, 0.78 and 0.76, differentiation between these two compounds mas not practical. The detection limit for pyridine-2-amidoxime was 1.0 bg. and 1.0 to 2.0 pg. for the other two isomers.
RESULTS A N D DISCUSSION
ACKNOWLEDGMENT
When a chromatogram of a mixture of the three pyridineamidoximes was treated with the Mohr's salt solution, only the pyridine-2-amidoxime reacts to give a red spot. This color is the result of the coordination of the ferrous ion with the diimine chromophoric group involving the nitrogen atom of the pyridine ring and the nitrogen of the amine portion of the amidoxime group. This is comparable to that found in 2,2'-bipyridyl and 1,lo-phenanthroline. This reagent therefore allows the detection of pyridine-2-amidoxime ( R , 0.87) in the presence of the 3- and 4-isomers. The second chromatogram, when treated with Sanger's reagent and alkali, shoxed a reaction for the 3- and 4-isomers whereas the reaction with pyridine-%amidoxime is negative.
The author thanks Reilley Tar and Chemical Corp. for samples of 3- and 4-cyanopyridine, LITERATURE CITED
(1) Jerchel, D., Jacobs, W., ilngew. Chem. 65, 342 (1953). ( 2 ) Kuffner, F., Faderl, K . j Monatsh. Chem. 86, 955 (1055). 13) llichaelib. L.. Be?. 24. 2439 11891). (4) I.. Furata., K../ ANAL. ~, RIorimoto. CHEM.34, 1033 il062). ( 5 ) Sanger, F., Biochem. J . 39, 507 (1945). ( 6 ) Tiemann, F., Rer. 17, 126 (1884). GEORGE A . PEARSE, JR. Chemistry Department Le Moyne College Syracuse, N. Y. 1J214 WORK slipported by research grant G 16002 from the National Science Foundation. VOL. 37, NO. 4, APRIL 1965
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