Hydrazine Solutions

The 40-45 per cent, hydrazine solution may be concentrated as follows. A mixture of 150 g. (144 ml.) of the solution and 230 ml. of xylene is distilled from a 500 ml. round-bottomed flask through a well-lagged Hempel (or other efficient fractionating) column fitted into a cork covered with tin foil. All the xylene passes over with about 85 ml. of water. Upon distillation of the residue, about 50 g. of 90-95 per cent, hydrazine hydrate (5) are obtained. 

The reaction represented is that with hydrazine solution, produced from hydrazine sulphate and sodium acetate in the presence of aqueous alcohol. Excellent results are also obtained by interaction of the commercially available 60-64 per cent, hydrazine solution with a solution of 2 4 dinitrochloro-benzene in triethylene glycol or in diethylene glycol at about 20°. 

Suspend 35 g. of finely-powdered hydrazine sulphate in 125 ml. of hot water contained in a 400 ml. beaker, and add, with stirring, 118 g. of crystallised sodium acetate or 85 g. of potassium acetate. Boil the mixture for 5 minutes, cool to about 70°, add 80 ml. of rectified spirit, filter at the pump and wash with 80 ml. of hot rectified spirit. Keep the filtered hydrazine solution for the next stage in the preparation. 

Equip a 1 Utre three-necked flask or a 1 litre bolt- head flask with a reflux condenser and a mercury-sealed stirrer. Dissolve 50-5 g. of commercial 2 4-dinitro-l-chlorobenzene in 250 ml. of rectified spirit in the flask, add the hydrazine solution, and reflux the mixture with stirring for an hour. Most of the condensation product separates during the first 10 minutes. Cool, filter with suction, and wash with 50 ml. of warm (60°) rectified spirit to remove unchanged dinitrochlorobenzene, and then with 50 ml. of hot water. The resulting 2 4-dinitrophenylhydrazine (30 g.) melts at 191-192° (decomp.), and is pure enough for most purposes. Distil oflF half the alcohol from the filtrate and thus obtain a less pure second crop (about 12 g.) recrystallise this from n-butyl alcohol (30 ml. per gram). If pure 2 4-dinitrophenylhydrazine is required, recrystallise the total yield from n-butyl alcohol or from dioxan (10 ml. per gram) this melts at 200° (decomp.). 

The following alternative method of preparation is recommended. Dissolve 50 g. of purified 2 4-dinitrochlorobenzene (1) in 100 ml. of triethylene glycol (gentle warming nia be necessary alternatively, 125 ml. of warm diethylene glycol may be used) in a 600 ml. beaker and cool, with mechanical stirring, in an ice bath to 15-18°. Place 15 ml. of commercial 60-65 per cent, hydrazine solution in a small separatory funnel supported over the beaker. Add the hydrazine solution to the stirred solution in the beaker at such a rate that the temperature is maintained between 15° and 20° (20-30 minutes). When... 

Benzil monohydrazone. Method 1. Boil a mixture of 26 g. of hydrazine sulphate, 55 g. of crystallised sodium acetate and 125 ml. of water for 5 minutes, cool to about 50°, and add 115 ml. of methyl alcohol. Filter off the precipitated sodium sulphate and wash with a little alcohol. Dissolve 25 g. of benzil (Section IV,126) in 40 ml. of hot methyl alcohol and add the above hydrazine solution, heated to 60°. Most of the benzil hydrazone separates immediately, but reflux for 30 minutes in order to increase the yield. Allow to cool, filter the hydrazone and wash it with a httle ether to remove the yellow colour. The yield is 25 g., m.p. 149-151° (decomp.). 

The estimated world production capacity for hydrazine solutions is 44,100 t on a N2H4 basis (Table 6). About 60% is made by the hypochlorite—ketazine process, 25% by the peroxide—ketazine route, and the remainder by the Raschig and urea processes. In addition there is anhydrous hydrazine capacity for propellant appHcations. In the United States, one plant dedicated to fuels production (Olin Corp., Raschig process), has a nominal capacity of 3200 t. This facihty also produces the two other hydrazine fuels, monomethyUiydrazine and unsymmetrical dimethyUiydrazine. Other hydrazine fuels capacity includes AH in the PRC, Japan, and Russia MMH in France and Japan and UDMH in France, Russia, and the PRC. 

Table 6. 1992 Hydrazine Solutions Production Capacity, N2H4, t...

World demand for hydrazine solutions is about 31,000 t N2H4, excluding Eastern Europe, Russia, and mainland China. The demand is ne ady... 

Shipment of hydrazine solutions is regulated in the United States by the Department of Transportation (DOT) which classifies all aqueous solutions between 64.4 and 37% N2H4 as "Corrosive" materials with a subsidiary risk of "Poison". Hydrazine has been identified by both the Environmental Protection Agency and the DOT as a hazardous material and has been assigned a reportable quantity (RQ) of 0.450 kg (1 lb) if spilled. Dmms for the shipment of these solutions must bear both the DOT specification "Corrosive" and "Poison" labels in association with the markings "RQ Hydrazine Aqueous Solution UN 2030." Aqueous solutions of 37% concentration or less are a hazard Class 6.1, UN 3293, Packing Group III and require "Keep Away From Food" placards and labels. 

Table 10. Materials Compatibility for Aqueous Hydrazine Solutions ...

Oxygen scavengers other than hydrazine are also used, especially catalyzed sodium sulfite, which reacts rapidly with oxygen even at room temperatures to form sodium sulfate. Catalyzed hydrazine formulations are now commercially available that react with oxygen at ambient temperatures at rates comparable to catalyzed sulfite (189). At elevated temperatures, the reaction rates are all similar. Table 14 Hsts the standard hydrazine solution products offered by Olin Corp. for sale to the water-treatment market. Other concentrations are available and other companies offer similar products. 

World production capacity of hydrazine solutions in 1995 (expressed as N2H4) was about 40000 tonnes, predominantly in USA 165(X) t, Germany 6400 t, Japan 6600 t and France 6KX) t. In addition some 32(X) t of anhydrous N2H4 was manufactured in USA for rocket fuels. 

The major commercial applications of hydrazine solutions are as blowing agents ( 40%), agricultural chemicals ( 25%), medicinals ( 5%), and — increasingly — in boiler water treatment now as much as 20%. The detailed pattern of usage, of course, depends to some extent on the country concerned. 

Historically, the most important ruthenium(II) ammine species is [Ru(NH3)5N2]2+, the first stable dinitrogen complex to be isolated (1965). It was initially obtained by refluxing RuC13 in hydrazine solution (but many... 

A 35% solution is colorless, has a pH level of 10.0, and has no flash point or fire point (important). A 65% hydrazine solution is approximately 100% hydrazine hydrate. Global producers include Bayer A.G., Elf Atochem S.A., and Olin Mathieson Corporation. 

Ammonia/hydrazine passivator An alkaline hydrazine solution (pH over 9.0, 0.5% N2H2) provides a useful passivator. If there are concerns over the use of hydrazine, diethylhydroxylamine (DEHA), erythorbate, or carbohydrazide may be substituted. Air blowing improves the passivating effect. 

In a factory manufacturing organo-iron and organo-manganese catalysts, use of cotton waste to mop up a spill of dilute hydrazine solution led to a spontaneous fire later. The fire was attributed to onset of rapid metal-catalysed decomposition of the hydrazine after sufficient water had evaporated from the waste, the traces of heavy metals originating from dust contamination, etc. 

B. t-Bulyl carbazate. In a 1-1. Erlenmeyer flask are placed 388.4 g. (2.0 moles) of phenyl <-butyl carbonate and 120.2 g. (2.4 moles) of a 64% hydrazine solution (Note 6). The mixture is swirled by hand and heated on a hot plate. When the internal temperature reaches 75-80°, it then rises rapidly and spontaneously to 104—110°, the two layers forming a dear solution. The solution is allowed to cool overnight. The mixture is then diluted with 500 ml. of ether and transferred to a separatory funnel in which it is shaken vigorously for about 10 minutes with a solution prepared from 160 g. (4.0 moles) of sodium hydroxide and 1.2 1. of water. The resulting two layers are placed in a 2-1. continuous extractor and extracted for 48 hours with ether. The ether solution is dried over magnesium sulfate, and the ether is removed by distillation from a water bath. The last portions of ether are removed with the aid of a water aspirator. The residual oil is then distilled using a Claisen flask with an air bath maintained at 115-125°. After 1 or 2 drops of fore-run the carbazate is collected at 61-65° (1.2 mm.), 24d 1.4518. The yield is 235-256 g. (89-97%) (Note 7). 

Aqueous hydrazine solutions, materials compatibility for, 13 587t Aqueous hydrazine specifications, 13 586t Aqueous hydrochloric acid reaction with metals, 13 826 thermodynamic functions of, 13 816t uses for, 13 834-835... 

Hydrazine perchlorate, 78 278 Hydrazine-sensitive detector, 3 812 Hydrazine solutions... 

In order to obtain a pure white hydrazine sulfate as the first precipitate, it is necessary to cool the hydrazine solution thoroughly and filter it twice before the sulfuric acid is added. Moreover, the sulfuric acid must be added slowly and with stirring. If these conditions are not followed, material containing brown particles results. 

It has been postulated that in the hydrazine solution (pH 8) the N-amino-4,6-dimethylpyrimidinium ion is partly deprotonated into its conjugate base, the resonance-stabilized ylide 31, so that in fact in this solution two equilibrated active species, 30 and 31, are present (62TL387 63AG604).The formation of an ylide intermediate was experimentally supported by the isolation of the dimer 2,4,7,9-tetramethyldipyrimido[l,2-fe r,2 -c]hexahydrotetrazine (32), which is formed when the pyrimidinium salt 30 is treated with liquid ammonia (Scheme III. 19). 

The action of an active intermediate oxidation product would explain another feature of the reaction. The reduction of silver ions by hydrazine is extremely sensitive to the presence of small amounts of copper. For example, a solution containing a mixture of silver nitrate, sodium sulfite and hydrazine which normally showed no sign of reduced silver for several minutes underwent almost immediate reaction when merely stirred with a clean copper rod. In the presence of gum arabic as stabilizer, streamers of colloidal silver passed out from the copper surface. Similarly, the addition of small amounts of cupric sulfate to a hydrazine solution eliminated the induction period of the reaction with silver chloride. 

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 hydrate is prepared by treating hydrazine sulfate, N2H4 H2SO4 with sodium hydroxide. The product is collected by distillation under nitrogen. It also is obtained as a by-product in the Bayer Ketazine process for producing hydrazine in which hydrazine solution is hydrolysed under pressure in a ketazine column. 

Hydrazine sulfate may be synthesized from aqueous ammonia and sodium hypochlorite solution in a two-step process. In the first stage, aqueous solution of ammonia is boiled with a normal solution of sodium hypochlorite in the presence of 10% gelatin solution to yield hydrazine. In the second stage, the hydrazine solution is ice-cooled followed by slow addition of concentrated sulfuric acid (Adams, R., and B.K. Brown. 1964. In Organic Synthesis, Collective Volume I, ed. H. Gilman and A. H. Blatt, 2nd ed. pp 309-310, New York John Wiley Sons). The reaction steps are as follows ... 

The electrochemical reduction behavior of 1102 was also studied in a nitric acid-hydrazine solution at a titanium electrode because of its resistance to corrosion in nitric acid [59]. It was necessary to pretreat the titanium electrode, to remove surface oxide, through cathodic... 

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