Gasometric Determination of Hydrazine and Derivatives HERBERT McKENNIS, Jr., JESSE
H. WEATHERBY,
and ELIZABETH P. DELLIS
Deparfment o f Pharmacology, Medical College o f Virginia, Richmond, Va.
b A number of hydrazino compounds give quantitative yields of nitrogen upon treatment with iodate. The reaction proceeds rapidly with monomethylhydrazine and the monoacyl hydrazines studied. In contrast, phenylhydrazine, which may b e determined quickly b y a titrimetric iodate reaction, yields nitrogen a t a slow rate which reflects the decomposition of the intermediate diazonium compound. 1,2Diacylhydrazines fail to yield nitrogen, but after hydrolysis yield nitrogen in the normal manner from the liberated hydrazine.
T
HI.: tlctcrniination of h>-drazine and man>- of its derivatives depends upoii the> reaction of hydrazine in 3 to 5-Y hj-drochloric acid solution with iodate ion to yield iodine chloride and one mole of nitrogen according to the equation :
N2H,
+ KI03 + 2HC1 KC1 + IC1 + S u + 3H20 +
This reaction ( 7 ) is the basis of a n accurate titrimetric method for determining hydrazine. An internal indicator which responds to a n excess of iodatc but not, to iodine and iodine chloride under condit'ions of the titration is often used ( 1 , 3 ) . The gencral nature of t h r iodate titration of hydrazine has been established by investigations whicah shon- that, in addition t o hydrazine, L: number of derirativcJs can be titratcd by suitable modification of t'he original Janiieson procedurc. I n 1939 Smith and K h e a t (16) studitld the quantitative deterniination of R variety of semicarbazoiies and rclated compountls. They reported generally satisfactory results with the iodate titration. The hydrazino nitrogen of tliioseniicarbazidr, however, could not be accurately assayed by the original or modificld procedure. Furfural seniicarbazone also gave unsatisfactory results. Miller and Furnian (13) carried out a potentiometric titration of semicarbazide and related compounds with iodate in the presence of mercuric chloride. The original and modified titration procedures have a wide range of usefulness, but are not convenient in complex biological mixtures. I n searching for other methods for the study and determination of a wide
variety of hydrazino compounds, satisfactory preliminary results were obtained by a manometric procedure (24). Both hydrazine and niethylhydrazine were determined nianonietrically in urine and other biological material (11). Although many hydrazine derivatives yield nitrogen quantitatively upon treatment with oxidizing agents, several apparent anomalies (8, 10, 15) point to the necessity for careful investigation of a variety of hydrazine derivatives. The present report is concerned with additional observations on the scope and limitations of a manometric iodate procedure for hydrazine compountls. EXPERIMENTAL
Hydrazine derivatives were Eastnian White Label grade. except as noted in Table I. Other chemicals n-ere analytical or reagent, grade. The 1,l-diiiiethylliydrazoiie of 771nitrobenzaldehyde was prepared hy adding I ,l-dimetli~.Ihydrazine(0.4 nil.. ;\Ietalectro Corp.. Laurel. Nd.) to st mixture of 500 nig. of 7n-nitrolienzaldehyde. 100 nil. of water, and 60 nil. of 95% ethanol. The solution became turbid in approviniately 30 minutes. Yubsequently a f e x small crystals ant1 :in oil were deposited. On standing o w r night bliese changed to long, slender .tals which were collected and air-dried. The yield of hydrazone (melting point 55.5-57') was 515 mg. (787,). The compound is soluble in chloroform. hexane. and niethanol. For analysis, a sample was recrystallized from 95% ethanol containing a little added n-ater (melting point 56-57") and then dried a t 3 min. and 35' over pot,assiuni hydroxitle. This conipound has also lieen rcported (23) to melt at' 45' C.aftcr recrystallization from methanol. Analysis. Calculated for C 9 H l i S 3 0 : XI 21.75. Found: K j 21.37. d solution of earh hylraziiie derivative (approximately 40 finioles) was prepared in 0.5 ml. of solvent (Table I). These solutions n-ere tested a t 37.00" z!= 0.01O in a Karburg apparatus equipped n i t h 15-nil. reaction vessels. The yessels contained the solution of sample. an excess of iodate (1 nil. of approximately 0.231 potassium iodate in 0 . 2 5 sulfuric acid) in the side arm, and 0.2 nil. of 40yG potassium hydroxide on a pleated filter paper (20) in the center well. The solutions were eyuilibrated in air (or nibrogen in certain cases given in Table I) before mixing. The thermobarometers contained all components except the hydrazine derivatives.
l l a n y of the compounds, such as hydrazine and methylhydrazine, reacted so rapidly that the minimum time for complete reaction could not' be detcrmined. RESULTS AND DISCUSSION
A high degree of precision was found when preliminary tests were made with hydrazine sulfate standard. The mean recovery of nitrogen from hydrazine sulfate in four determinations !vas 99.5 with a standard error of *1.2. Typical results with hydrazine and its derivatives are given in Table I. The ready availability of high quality hydrazine sulfate has led other workers ( 1 8 , 21) to employ hydrazine in the standardization of gasometric apparatus. 1Iethylliytlrazine sulfate also gave a hydrazine nitrogen value (average 99.8%) corresponding c~loscly to the theorebical. The inethylhydrazinc SUIfate of the sample employed had a nectralization PquivaIcwt (1I) of 144.28 (calculated 144.15). The reaction of hydrazine and nietli~.lli~-clraziiiewith s practical purp acidic iodate n - ~for instantanrous. The potentiometric analytical methods for hydrazine compounds folIOTT the equation: 5l;yHi
+ 4x103 + 2H3SOA a i s ? + 21%+ 2KZS04 + 1 2 H 4 --L
rvhicli prevails when hydrazine is titrated in sulfuric acid solution. There appears to be a paucity of data upoii the fate of organic substituents where substituted hydrazino compounds undergo oxidations under comparable conditions. S o attempt was niade to detect methanol (12) or methyl iodide u-hich ma!. be protlucd when methylhyclrazine and iodate rcvict. If these products are formed. they do not affect the niancmetric determination. The evolved gases in all instances have been referrd to as nitrogen in this paper. Miller and Furman ( I S ) in studying the reaction of phenylhydrazine with iodate and hydrochloric acid were ablc to formulate the reaction 5CsHbXHSH2
+ 4I
