January, 19631 BARAKAT AND MONIER SHAKER 59 The Micro-determination of Hydrazine Salts and Certain Derivatives BY M. 2. BARAKAT AND MONIER SHAKER (Biochemistry Department, Faculty of Veterinary Medicine, Cairo University, Giza, Cairo, Egypt) In the presence of dilute sulphuric acid, N-bromosuccmimide readily and quantitatively oxidises aqueous solutions of hydrazine salts and certain derivatives. The reaction takes place a t room temperature, and N-bromo- succinimide is irreversibly reduced to succinimide. The mechanism of the reaction is discussed. The determination of hydrazine sulphate, phenyl- hydrazine hydrochloride and phenylhydrazine-P-sulphonic acid by titration with standard N-bromosuccinimide solution is described ; the experimental error does not exceed &2 per cent.Results are reported for comparative analysis of hydrazine sulphate and phenylhydrazine hydrochloride by the proposed method and by the generally accepted potassium iodate method. VARIOUS titrimetric,lj3 colorimetric3 and p~tentiometric~ methods have been described for determining hydrazine salts, and the oxidation of hydra~ine~3~3’ has been widely used as the basis of techniques for its measurement. The titrimetric methods suffer from certain defects, e.g., oxidation of hydrazine in alkaline solution with potassium permanganates gives inaccurate results in the absence of barium and telluric acid. The end-point in the chloramine B methodg is indistinct; in the presence of an excess of potassium bromide the end-point is sharp and accurate results can be obtained. There is some doubt about the reliability of the potassium iodate meth0d.~910 The investigation described here deals with the micro-determination of hydrazine salts, e.g., hydrazine sulphate and certain derivatives such as phenylhydrazine hydrochloride and phenylhydrazine-p-sulphonic acid, by the use of N-bromosuccinimide. The method is based on the fact that N-hromosuccinimidell readily and quantitatively oxidises an aqueous solution of hydrazine sulphate and is itself reduced to succinimide, with the evolution of nitrogen and the formation of hydrogen bromide, as represented by the equation- CH,--CO 2 1 \NBr + H,N-NH,.H2S0,+ CH,-CO/ CH,-CO 2 1 \NH + 2HBr + N, + H,SO, CH,-CO/ The reaction proceeds quantitatively in aqueous solution at room temperature in the ratio of two molecules of N-bromosuccinimide to one molecule of hydrazine sulphate. Effervescence owing to evolution of nitrogen is perceptible.Succinimide has been isolated from the reaction mixture and identified by melting-point and mixed melting-point determinations. The presence of hydrogen bromide and sulphuric acid in the reaction mixture has been confirmed. Similarly, N-bromosuccinimide is quantitatively and rapidly reduced to succinimide by phenylhydrazine12 or phenylhydrazine-9-sulphonic acid at room temperature, in accordance with the equation- CH2-CO \NBr + ZH,N.NH.R---+ C!H,----CO/ where R can be C,H,- or HO,S.C,H,-. With hydrazine derivatives, e.g., phenylhydrazine, bromine is formed, not hydrogen bromide as is formed with hydrazine sulphate.A’-Bromosuccinimide is a highly selective oxidising agent1, 3 1 4 and can decolorise methyl red in aqueous acid medium, but it oxidises hydrazine salts or derivatives preferentially. Until all the hydrazine salt or derivative present has been oxidised, the red colour of the60 BARAKAT AND MONIER SHAKER : MICRO-DETERMINATION [.4 nalySt, V O l . 88 indicator does not disappear. The slightest excess of N-bromosuccinimide added after all the hydrazine salt or derivative has been oxidised decolorises the methyl red. Methyl red has been used previously as an indicator in titrations involving the use of bromine15 and N-bromosuccinimide. l6 Comparative determinations of hydrazine salts have been carried out by the proposed method and the most generally accepted potassium iodate method.N-Bromosuccinimide is analogous to potassium iodate; it acts as an oxidising agent, but is better than iodate in that it can be used for determining extremely small amounts of hydrazine salts or deriva- tives. The potassium iodate method cannot be used for determining amounts of hydrazine salts less than 30 mg, whereas the proposed method will determine amounts as low as 500 pg. EXPERIMENTAL REACTION BETWEEN N-BROMOSUCCINIMIDE AND HYDKAZINE SULPHATE- A 1-3013-g portion of hydrazine sulphate (0.01 mole) was dissolved in 20 ml of distilled water, and 3.56 g of N-bromosuccinimide (0.02 mole) were dissolved in 200 ml of hot distilled water. When the N-bromosuccinimide solution was cool, it was added gradually, with shaking, to the cold hydrazine sulphate solution.During the addition a strong effervescence was observed owing to evolution of nitrogen. When the bubbles of gas had ceased, the reaction mixture was a colourless solution. The presence of hydrobromic acid was established by treating 10 ml of the colourless solution with nitric acid and 10 per cent. silver nitrate solution; a yellowish white precipitate of silver bromide was deposited. The presence of sulphuric acid was confirmed by treating 10 ml of the colourless solution with hydrochloric acid and 10 per cent. barium chloride solution ; a white precipitate of barium sulphate was observed. Succinimide was isolated by distilling in vacuo the remaining 200 ml of the colourless solution and crystallising the solid residue from benzene. Melting-point and mixed melting- point determinations with an authentic sample showed that the colourless crystals obtained were succinimide.VALIDITY OF THE REACTION FOR QUANTITATIVE DETERMINATION- Before applying the reaction to the determination of hydrazine salts or derivatives in test solutions, we decided to verify quantitatively the reaction between N-bromosuccinimide and hydrazine sulphate. An accurately measured volume of solution containing 0.13013 g (1 millimole) of hydrazine sulphate per 100 ml was placed in a 25-ml conical flask, and an equal volume of 10 per cent. v/v sulphuric acid and 2 drops of 0.04 per cent. methyl red indi- cator solution in 95 per cent. ethanol were added. The mixture was titrated with 0-1 per cent. w/v N-bromosuccinimide solution, added dropwise from a microburette, with continuous shaking after each addition.When the red colour of the indicator faded, another drop was added, and the titration was continued until the red colour completely disappeared. A similar series of experiments was carried out with N-bromosuccinimide solution containing twice the number of molecules of solute as in the first solution. I t was found that the reaction was stoicheiometric in the presence of dilute sulphuric acid at room temperature; the results were- Volume of hydrazine sulphate solution (1 mmole per 100 ml), ml 10 5 4 3 2 1 Titre of N-bromosuccinimide (1 mmole per 100 ml), ml . . . . 20.25 10.15 8.12 6.18 4-11 2.06 Titre of N-bromosuccinimide (2 mmole per 100 ml), ml . . . . 10.13 5-10 4.09 3.08 2.05 1.02 The equimolecular solutions of hydrazine sulphate and N-bromosuccinimide (freshly The prepared) were then diluted ten-fold with distilled water in 100-ml calibrated flasks.diluted solutions were titrated as before and gave reproducible results. REAGENTS- METHOD Methyl red solution, 0.04 per cent. w / v in 95 per cent. ethanol. Dilute sulphuric acid, 10 per cent. v / v . Dilute hydrochloric acid, 10 per cent. v / v . N-Rromosuccinimide solution, 0-1 per cent. w / v , aqueous-This solution should be freshly prepared before use.January, 19631 OF HYDRAZINE SALTS AND CERTAIN DERIVATIVES 61 PROCEDURE- To an accurately measured volume, e.g., 5 ml, of the hydrazine sulphate solution in a 50-ml conical flask add an equal volume of dilute sulphuric acid and 5 drops of methyl red indicator solution.Titrate the mixture with 0.1 per cent. w/v X-bromosuccinimide solution, added dropwise from a microburette graduated at 0.01-ml intervals, with continuous shaking. The end-point is reached when the last drop of titrant discharges the red colour. Calculate the hydrazine sulphate content of the sample solution from the expression- HYdrazine sulphate present, mg or pg = 130.13 VC/356 where V is the titre of N-bromosuccmimide solution in millilitres and 0' is the concentration of the N-bromosuccinimide solution in mg or pg per ml. APPLICATIONS OF THE METHOD DETERMINATION OF HYDRAZINE SLJLPHATE- A 0-5 per cent. stock solution of hydrazine sulphate was prepared by dissolving 0.5 g of pure hydrazine sulphate, obtained from E. Merck A.G., Darmstadt, Germany, in distilled water, and the volume was adjusted to 100ml with distilled water in a calibrated flask.Solutions containing 0.4, 0-3, 0.2 and 0.1 per cent. of hydrazine sulphate were prepared by suitable dilutions of portions of this solution. The hydrazine sulphate contents of these solutions were then determined by the proposed method; the results are shown in Table I. TABLE I RECOVERY OF HYDRAZINE SULPHATE BY THE PROPOSED METHOD Concentration of hydrazine sulphate solution, % w/v 0.5 0.4 { 0.3 { 0.2 { 1 i 0.1 i Volume of solution used, ml 1 2 3 1 2 1 2 1 2 1 2 3 4 5 6 7 8 9 10 H ydrazine sulphate content, mg 5 10 15 4 8 3 6 2 4 1 2 3 4 5 6 7 8 9 10 Titre of 0- 1 per cent. w/v N-bromosuccinimide solution, ml 13.55 27.00 40.50 11.05 22.25 8.30 16.55 5.55 11-05 2-70 5.47 8.34 11.05 13.80 16.25 18.95 21-70 24.45 27.10 H ydrazine sulphate found, mg 4.95 9-87 14-80 4.04 8.13 3.03 6.05 2.03 4.04 0.99 2.00 3.05 4.04 5-04 5.94 6.93 7.93 8.94 9.9 1 Error, 1.00 1.30 1.33 1.00 1.63 1.00 0.83 1.50 1.00 1.00 1.66 1.00 0.80 1.00 1.00 0-88 0.75 0.90 Y O - The 0.1 per cent.hydrazine sulphate solution was then diluted ten-fold with distilled water in a 100-ml calibrated flask and the diluted solution (0.01 per cent.) was titrated with 0-05 per cent. w/v N-bromosuccinimide solution; the results are shown in Table 11. TABLE I1 MICRO-DETERMINATION OF HYDRAZINE SULPHATE BY THE PROPOSED METHOD Volume of hydrazine sulphate solution used, ml 10 9 8 7 6 6 Hydrazine sulphate present, Pg 1000 900 800 700 600 500 Titre of 0.05 per cent.N -bromosu ccinimide solution, ml 5.45 4.90 4.35 3.80 3-30 2.70 Hydrazine sulphate found, t% 996.26 895-72 795.18 694.64 603.24 493.56 Error, 0.37 0.47 0.60 0.77 0.52 1-29 Y O62 BARAKAT ,4ND MONIER SHAKER: MICRO-DETERMINATION [AYtdySt, VOl. 88 The proposed method was compared with the iodate method by titrating a 1 per cent. hydrazine sulphate solution with 0.5 per cent. N-bromosuccinimide solution and with 0.025 M potassium iodate; the results are shown in Table 111. TABLE I11 COMPARISON OF RESULTS BY PROPOSED AND IODATE METHODS 1 ml of 0.025 M potassium iodate = 3.253 mg of hydrazine sulphate 1 ml of 0.5 per cent. N-bromosuccinimide = 1.8275 mg of hydrazine sulphate With 0.025 M potassium iodate as titrant With 0.5 per cent. N-bromosuccinimide as titrant A I H ydrazine ’ r- Volume of 1 per cent.Hydrazine w/v hydrazine sulphate sulphate sulphate sulphate solution taken, content, Titre, found, Error, Titre, found Error, ml mg ml mg % ml mg Y O 10 9 8 7 6 5 4 3 2 1 0.5 100 90 80 70 60 50 40 30 20 10 5 55.40 50.10 44.10 38.50 33.10 27.60 22.10 16.60 10.90 5.50 2.76 101-24 91-56 80.59 70.36 60.49 50.44 40.39 30.34 19.92 10.05 5.04 1-24 1.73 0.74 0.51 0.82 0.88 0.98 1.13 0.40 0.50 0.80 30-55 27.60 24-50 21.55 18.40 15.20 12-45 9.35 6-30 2.95 1.70 99-38 89.78 79.70 70-10 59.86 49.45 40.50 30.42 20.49 9.60 5.53 0.62 0.24 0.43 0.14 0.23 1.10 1.25 1-40 2.45 4.00 10.60 DETERMINATION OF PHENYLHYDRAZINE HYDROCHLORIDE- Before the proposed method was applied to determining phenylhydrazine hydrochloride, it was decided to verify quantitatively the reaction between N-bromosuccinimide and phenyl- hydrazine hydrochloride. It was assumed that one molecule of phenylhydrazine hydrochloride was oxidised by two molecules of N-bromosuccinimide.Accordingly, a solution containing 0-1445 g (1 millimole) of phenyhydrazine hydrochloride per 100 ml was titrated with solutions containing 0.178 and 0.356 g (1 and 2 millimoles, respectively) of N-bromosuccinimide. It was found that the reaction between phenylhydrazine hydrochloride and N-bromosuccinimide was quantitative in the molecular concentrations expected; the results were- Volume of phenylhydrazine hydrochloride (1 mmole per 100 ml), ml 10 5 4 3 2 1 Titre of N-bromosuccinimide solution (1 mmole per 100 ml), ml . . 19.95 9.95 8.05 6.05 3-95 2.05 Titre of N-bromosuccinimide solution (2 mmoles per 100 ml), ml .. 10 5 4 3 2 1 A series of experiments was carried out in which a 0.1 per cent. w/v solution of phenyl- hydrazine hydrochloride was titrated by the proposed method with 0.1 per cent.iV-bromo- succinimide; the results are shown in Table IV. TABLE IV RECOVERY OF PHENYLHYDRAZINE HYDROCHLORIDE BY PROPOSED AND IODATE METHODS 1 ml of 0-1 per cent. N-bromosuccinimide = 0.4059 mg of phenylhydrazine hydrochloride 1 ml of 0.025 M potassium iodate = 3.612 mg of phenylhydrazine hydrochloride With 0.025 M potassium iodate as titrant With 0.1 per cent. N-bromosuccinimide as titrant h A I > I \ Phen ylhydrazine Phen ylhydrazine Phen ylhydrazine hydrochloride hydrochloride hydrochloride present, Titre, found, Error, Titre, found, Error, 10 24.45 9.92 0.80 2.45 8.85 11-50 9 22.00 8.93 0.78 2-15 7.77 13.67 8 19.65 7.98 0.25 1.90 6.86 14-25 7 17-03 6.9 1 1.29 1.70 6-14 12-29 6 14.60 5.93 1-17 1-55 5-60 6-67 5 12.13 4-92 1-60 1.25 4.52 9.60 mg ml mg Y O ml mg %January, 19631 OF HYDRAZINE SALTS AND CERTAIN DERIVATIVES 63 DETERMINATION OF PHENYLHYDRAZINE-@-SULPHONIC ACID- was oxidised by two moles of N-bromosuccinimide; the results obtained were- It was ascertained quantitatively that one molecule of phenylhydrazine-$-sulphonic acid (1 mmole per 100 ml), ml .. .. . . . . 10 5 4 3 2 1 Volume of phenylhydrazine-p-sulphonic acid solution Titre of N-bromosuccinimide solution (1 mmole per 100 ml), ml.. . . . . . . . . . . . . 20.08 10.05 8.04 6-02 4-05 2.05 A 0.1 per cent.solution of phenylhydrazine-9-sulphonic acid was titrated by the proposed method with 0.1 per cent. N-bromosuccinimide solution; the results are shown in Table V. TABLE V DETERMINATION OF PHENYLHYDRAZINE-@-SULPHONIC ACID BY THE PROPOSED METHOD 1 ml of 0.1 per cent. N-bromosuccinimide = 0.5284 mg of phenylhydrazine-9-sulphonic acid Volume of phenylhydrazine-p- sulphonic acid solution, ml 10 9 8 7 6 5 4 3 2 1 Phenylhydrazine-p- sulphonic acid present, mg 10 9 8 7 6 5 4 3 2 1 Titre of 0.1 per cent. w/v N-bromosuccinimide, ml 18.85 17.00 15.20 13.15 11.35 9.40 7.65 5.70 3.75 1.86 Phenylhydrazine-p- sulphonic acid found, mg 9.96 8.98 8-03 6.95 6-00 4-97 4.04 3.0 1 1.98 0.98 Error, 0.40 0.22 0.38 0-7 1 0.60 1.00 0.33 1.00 2.00 O / / O - DISCUSSION OF RESULTS The accuracy of the generally accepted potassium iodate method depends mainly on the concentration of hydrazine sulphate in the sample solution.Results show that the experimental error appears to increase as the concentration of hydrazine sulphate in the sample solution decreases. Moreover, the potassium iodate method cannot be used for determining amounts of hydrazine sulphate less than 30 mg (see Table 111) ; further, it is difficult to detect the end-point when the iodate method is applied to low con- centrations of hydrazine salts. The results in Tables I11 and IV show that the proposed method is superior to the potassium iodate method in accuracy and sensitivity. 1. 2. 3. 4. 5. 6 . 7 . 8. 9. 10. 11. 12. 13. 14. 15. 16. REFERENCES Kolthoff, I. M., J . Amer. Chem. Soc., 1924, 46, 2009. Singh, B., and Singh, A., Anal. Chim. Acta, 1953, 9, 22. Bapat, M. G., and Tatwawadi, S. V., J . Sci. Research Banaras Hindu Univ., 1956-55, 7, 235. Britton, H. T. S., and Konigstein, M., J . Chem. Soc., 1940, 673. Jilek, A., and BrandStetr, J., Chem. Zvesti, 1953, 7, 611. Suseela, B., Ber., 1955, 88, 23. Endroi, P., Magyar Ke'm. Foly., 1953, 59, 211; Chem. Abstr., 1954, 48, 505. Issa, 1. M., and Issa, R. M., Anal. Chim. Acta, 1956, 14, 578. Paul, R. C., and Singh, A., J . 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