NH2OH

HYDROXYLAMINE  , or hydroxy-ammonia, a compound prepared in 1865 by W . C . Lossen by the reduction of ethyl nitrate with tin and hydrochloric acid . In 187o E . Ludwig and T . H . Hein (Chem . Centralblatt, 187o, 1, p . 340) obtained it by passing nitric oxide through a series of bottles containing tinand hydrochloric acid, to which a small quantity of platinum tetrachloride has been added; the acid liquid is poured off when the operation is completed, and sulphuretted hydrogen is passed in; the tin sulphide is filtered off and the filtrate evaporated . The residue is extracted by absolute alcohol, which dissolves the hydroxylamine hydrochloride and a little ammonium chloride; this last substance is removed as ammonium platinochloride, and the residual hydroxylamine hydrochloride is recrystallized . E . Divers obtains it by mixing cold saturated solutions containing one molecular proportion of sodium nitrate, and two molecular proportions of acid sodium sulphite, and then adding a saturated solution of potassium chloride to the mixture .

After

standing for twenty-four hours, hydroxylamine potassium disulphonate crystallizes out . This is boiled for some hours with water and the solution cooled, when potassium sulphate separates first, and then hydroxylamine sulphate . E . Tafel (Zeit. anorg . Chem., 1902, 31, p . 289) patented an electrolytic process, wherein 5o% sulphuric acid is treated in a divided cell provided with a cathode of amalgamated lead, 5o% nitric acid being gradually run into the cathode compartment . Pure anhydrous hydroxylamine has been obtained by C . A . Lobry de Bruyn from the hydrochloride, by dissolving it in absolute methyl alcohol and then adding sodium methylate . The precipitated sodium chloride is filtered, and the solution of hydroxyl-amine distilled in order to remove methyl alcohol, and finally fractionated under reduced pressure . The free base is a colourless, odourless, crystalline solid, melting at about 3o° C., and boiling at 58° C . (under a pressure of 22 mm.) .

It deliquesces and oxidizes on exposure, inflames in dry

chlorine and is reduced to ammonia by zinc dust . Its aqueous solution is strongly alkaline, and with acids it forms well-defined stable salts . E . Ebler and E . Schott (J. pr . Chem., r9o8, 78, p . 289) regard it as acting with the formula NH2.OH towards bases, and as NH3:0 towards acids, the salts in the latter case being of the oxonium type . It is a strong reducing agent, giving a precipitate of cuprous oxide from alkaline copper solutions at ordinary temperature, converting mercuric chloride to mercurous chloride, and precipitating metallic silver from solutions of silver salts . With aldehydes and ketones it forms oximes (q.v.) . W . R . Dunstan (Jour .

Chem .

Soc., 1899, 75, p . 792) found that the addition of methyl iodide to a methyl alcohol solution of hydroxylamine resulted in the formation of trimethyloxamine, N(CH3)30 . Many substituted hydroxylamines are known, substitution taking place either in the a or # position (NH2.OH) . 9-phenylhydroxylamine, C6HSNH•OH•, is obtained in the reduction of nitrobenzene in neutral solution (e.g. by the action of the aluminium-mercury couple and water), but better, according to C . Goldschmidt (Ber., 1896, 29, p . 2307) by dissolving nitrobenzene in ten times its weight of ether containing a few cubic centimetres of water, and heating with excess of zinc dust and anhydrous calcium chloride for three hours on a water bath . It also appears as an intermediate product in the electrolytic reduction of nitrobenzene in sulphuric acid solution . By gentle oxidation it yields nitrosobenzene . Derivatives of the type R2N.OH result in the action of the Grignard reagent on amyl nitrite . Dihydroxy-ammonia or nitroxyl, NH(OH)2, a very unstable and highly reactive substance, has been especially studied by A . Angeli (see A .

W .

Stewart, Recent Advances in Physical and Inorganic Chemistry, 1909) .