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HYDROXYLAMINE.

Free hydroxylamine, NH_{2}OH, has been isolated by M. Lobry de Bruyn, and a preliminary account of its mode of preparation and properties is published by him in the current number of the Recueil des travaux chimiques des Pays-Bas (1891, 10, 101).  The manner in which the free base was obtained was briefly as follows.  About a hundred grammes of hydroxylamine hydrochloride, NH_{2}OH.HCl, were dissolved in six hundred cubic centimeters of warm methyl alcohol.  To this solution a quantity of sodium dissolved in methyl alcohol was added, in such proportion that the hydrochloride of hydroxylamine was present in slight excess over and above that required to convert it to sodium chloride.  After deposition of the separated sodium chloride the solution was decanted and filtered.

The greater portion of the methyl alcohol was next removed by distillation under the reduced pressure of 160-200 mm.  The remainder was then treated with anhydrous ether, in order to completely precipitate the last traces of dissolved sodium chloride.  The liquid eventually separated into two layers, an upper ethereal layer containing about 5 per cent. of hydroxylamine, and a lower layer containing over 50 per cent. of hydroxylamine, the remainder of the methyl alcohol, and a little dissolved salt.  By subjecting this lower layer to fractional distillation under 60 mm. pressure, it was separated into three fractions, of which the first contained 27 per cent. of hydroxylamine, the second 60 per cent., and the third crystallized in the ice-cooled receiver in long needles.  This third fraction consisted of free solid NH_{2}OH.  Hydroxylamine as thus isolated in the free state is a very hygroscopic substance, which rapidly liquefies when exposed to air, owing to the absorption of water.

The crystals melt at 33 deg., and the fused substance appears to possess the capability of readily dissolving metallic salts.  Sodium chloride is very largely soluble in the liquid; powdered niter melts at once in contact with it, and the two liquids then mix.  Free hydroxylamine is without odor.  It is heavier than water.  When rapidly heated upon platinum foil it suddenly decomposes in a most violent manner, with production of a large sheet of bright yellow flame.  It is only very slightly soluble in liquid carbon compounds, such as chloroform, benzene, ether, acetic ether, and carbon bisulphide.  The vapor attacks corks, so that the solid requires to be preserved in glass-stoppered bottles.  The free base appears also to act upon cellulose, for, upon placing a few drops of the melted substance upon filter paper, a considerable amount of heat is evolved.  The pure crystals are very stable, the base in the free state appearing to possess much greater stability than when dissolved in water.  The instability of the solution appears, however, to be influenced to a considerable extent by the alkalinity of the glass of the containing vessel, for concentrated solutions free from dissolved alkali are found to be perfectly stable.  Bromine and iodine react in a remarkable manner with free hydroxylamine.