Hydrazine measurement

It is therefore clear that reliable and sensitive analytical methods are needed for the determination of hydrazine and its derivatives. Techniques have been developed for hydrazine measurements based on spectrophotometry [5], fluorimetry [6], chemiluminescence [7], and chromatography [8]. However, drawbacks of these procedures include diflhcult sample preparation, the need for derivatization, and insufficient sensitivity, which limit their utility. In contrast, electrochemical methods generally present the advantages of simplicity and high sensitivity. 

Structural data of a diaziridine come from gas phase electron diffraction measurements (74CC397). The N—N bond of 3-methyldiaziridine (24) is longer than in hydrazine (1.449 A) the C—N bond distances in (24) and in diazirine are nearly equal (1.479 versus 1.482 A),... 

By far the best efforts to measure product compns were made by Orncllas co-workers (Refs 3, 4 6) who made accurate calorimetry and compn measurements on highly confined and unconfined expl samples. The expls he studied were PETN, HMX, NM, TNT, Bis(2,2-dinitro-2-fluoroethyl)formal (FEFO), l,2-Bis(difluoro-amino) propane (1,2 DP), Benzotrifuroxan (BTF), LX-11-0 (80.1/19.9 HMX/Viton), XTX-8003 (80/20 PETN/Sylgard 182), and three Hydrazine Nitrate (HN) mixts. Of course, most of these measured compns are not CJ products, but reequilibrated mixts of CJ products at some frozen equilibrium temp Tfr < TCJ... 

Although the high reactivity of hydrazine presented substantial problems regarding accurate and consistent measurement of experimental concentrations (see Section 3), this high reactivity does not appear to reside with monomethylhydrazine. 

This is the dominant overall reaction for the decomposition on platinum or tungsten at 200 and 380 °C, respectively40. Most workers on hydrazine decomposition flames41-44, in which the reactions are homogeneous, report a stoichiometric equation similar to (b) for final flame temperatures up to 1900 °K. Measurements of MacLean and Wagner45 on decomposition flames and of Husain and Norrish37 on the flash photolysis of hydrazine indicate the contribution of the overall reaction... 

To investigate the electrochemical properties of pure ruthenium also, ruthenium was chemically reduced and deposited as a thick layer on a platinum wire becaiise ruthenixim metal is not commercially available as a wire nor a plate due to its brittleness. A platinum wire (0.1 mm in diameter) was placed in an alkaline 0.05 M ruthenium (IQ) nitrosylnitrate solution containing 1 M hydrazine as a reducing agent and heated up to 60°C. The deposition did not start imtil the heat was applied. After the deposition, the electrode was washed with water and used for the electrochemical measurements. 

Ruthenium catalysts, supported on a commercial alumina (surface area 155 m have been prepared using two different precursors RUCI3 and Ru(acac)3 [172,173]. Ultrasound is used during the reduction step performed with hydrazine or formaldehyde at 70 °C. The ultrasonic power (30 W cm ) was chosen to minimise the destructive effects on the support (loss of morphological structure, change of phase). Palladium catalysts have been supported both on alumina and on active carbon [174,175]. Tab. 3.6 lists the dispersion data provided by hydrogen chemisorption measurements of a series of Pd catalysts supported on alumina. is the ratio between the surface atoms accessible to the chemisorbed probe gas (Hj) and the total number of catalytic atoms on the support. An increase in the dispersion value is observed in all the sonicated samples but the effect is more pronounced for low metal loading. 

Isoniazid, carbidopa, and hydralazine are hydrazine derivatives with therapeutic uses. They form Schiff bases with pyridoxal 5 -phosphate, and rate constants for their formation and hydrolysis have been measured in aqueous solution pH-rate profiles are reported and compared with that of hydrazine itself. 

The most common assay uses 3a-hydroxysteroid dehydrogenase to form the 3-keto bile acid that is trapped by, for example, hydrazine hydrate, causing the reaction to go to completion. The co-factor NAD is reduced stoichiometrically and can be measured by ultraviolet absorption or more commonly by fluorescence at an activation of 345 nm and emission of 450 nm. Use of this enzyme measures all bile acids with a 3a-hydroxyl but not cholesterol, which has a 3p-hydroxyl, and does not measure bile acids with a sulphate or glucuronide group conjugated to the 3a-hydroxyl. 

This is the reason why, for example, the zero order formic acid dehydrogenation may easily be measured on bulk metal catalysts at 200-300°C. whereas the approximately first order ethanol dehydrogenation requires highly activated porous metals of large specific surface in order to become measurable under the same conditions. The same has been shown for the decomposition of formaldehyde, acetic acid, and hydrazine hydrate. In these cases, the fractional surface coverage is simply 1000 times lower than in the case of a zero order reaction. 

Hydrazine may be analyzed by various methods including GC-FID, GC-NPD, HPLC, GC/MS, polarography, colorimetry, and iodometric titrations. The iodometric method is simple and apphcable to measure hydrazine quantitatively in water at aU concentrations. 

Hydrazine reduces iodine to hydrogen iodide. Thus, an excess of standard solution of iodine is added to a measured volume of aqueous hydrazine solution and the excess iodine is back titrated at pH 7.0 to 7.2 (buffered by sodium bicarbonate) against a standard solution of sodium thiosulfate using starch indicator. 

Hydrazine solutions may be analyzed by various colorimetric methods. Low concentrations of hydrazine in aqueous samples at ppm level may be determined by treating the sample with an acidified solution of dimethyl-aminobenzaldehyde and the absorbance of color formed is measured at 485 nm with a spectrophotometer. 

Hydrazine sulfate is used as a reducing agent in analytical chemistry for gravimetric measurement of nickel, cobalt, and other metals, and in peptide analysis in the separation of polonium from tellurium as an antioxidant in... 

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