HYDROXYLAMINE, NH2OH

This article appears in Volume V14, Page 171 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: HOR-I25

HYDROXYLAMINE, NH2OH , 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

OXIDE

through a

series

SERIES (a Latin word from serere, to join)

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

HYDROXYLAMINE, NH2OH

hydrochloride and a little ammonium chloride; this last substance is removed as ammonium platinochloride, and the residual

hydroxylamine

HYDROXYLAMINE, NH2OH

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

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

OXIDE

from alkaline copper solutions at

ordinary

ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

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, C6HSNHOH, 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

WEIGHT

of ether containing a few cubic centimetres of water, and

heating

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

RECENT

Advances in Physical and Inorganic Chemistry, 1909).

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