Sulphonic Derivatives of Hydroxylamine

The potassium salt of hydroxylamine αββ-trisulphonic acid is made by oxidising that of the ββ-disulphonic acid with lead peroxide or silver oxide in alkaline solution. Thus:

3HO-N(SO₃K)₂ + KOH + PbO₂ = 2{(SO₃.K)-O-N(SO₃K)₂} + KNO₃ + 2Pb(OH)₂.

The reaction probably proceeds through an intermediate violet-coloured nitroso-disulphonate,

ON-(SO₃K)₂ or (KSO₃)₂-NO-NO-(SO₃K)₂.

A preparation of the potassium salt of the trisulphonic acid has been described in detail. 1200 c.c. of 5N sodium bisulphite is added with stirring to a mixture of 1000 grams of ice and 150 grams of commercial sodium nitrite, the temperature not being allowed to rise above 5° C. The solution is well shaken with 600 grams of lead peroxide and warmed on a water-bath, with continued shaking. The solution is filtered, the filtrate warmed with 800 grams of technical potassium chloride, and the precipitated PbCl₂ filtered off. The filtrate, after three days, deposits the potassium salt in monoclinic prisms. It is dried on porous plates and over calcium chloride.

The salt crystallises with 1½ mols. of water and is easily soluble in water. The sodium salt crystallises with 2 mols. of water (monoclinic) and the ammonium salt with 1½ mols. of water (rhombic). The neutral or alkaline solutions are stable. The acid solutions are hydrolysed on warming, giving as a first product a salt of the αβ-disulphonic acid, KO-SO₂-O-NH-SO₃K. This is isomeric with the ββ-disulphonate, but differs from it by crystallising anhydrous, and giving no colour with alkaline lead peroxide. It is distinguished from the trisulphonate by its stability at 100° C. The sodium and ammonium salts are also known.

The preparation of the αβ-sulphonate is effected by dissolving 423 grams of the dry trisulphonate in 800 c.c. of boiling water which contains 1 c.c. of dilute HCl. Any lead sulphate is removed, and the filtrate deposits the potassium salt in colourless crystals, the yield being about 90 per cent, of the theoretical. The salts contain three atoms of alkali metal per molecule of compound or atom of nitrogen, and it is therefore to be supposed that the hydrogen of the imino-group is also replaced, giving, e.g., SO₃K-O-NK-SO₃K.2H₂O. The partial hydrolysis of this compound may possibly give the mono-α-sulphonic acid, (SO₃H)-O-NH₂, since the solution at one stage sets free iodine from potassium iodide, a reaction which does not take place with hydroxylamine itself or with the β-acid. The α-acid might, however, behave as an oxidising agent, since it may be regarded as the amide of permono-sulphuric acid, (SO₃H)-O-OH. This a, or isosulphonic acid has been prepared as a microcrystalline powder by the action of chlorsulphonic acid on hydroxylamine hydrochloride.