Home >> Encyclopedic Dictionary Of Photography >> Formula to Or Film Negative Process >> Hydroxylamine Hydrochloride

Hydroxylamine Hydrochloride

developer, solution and alkaline

HYDROXYLAMINE HYDROCHLORIDE (Formula, molecular weight, 69.5; synonym, oxyammonium tubular crystals, very soluble in water and alcohol.

The best method of preparing it is probably the following, given by Ruschig: Hydrogen sulphite in concentrated aqueous solution is added to an alkaline nitrate at a temperature not exceeding freezing if the soda salt be used, or 4o deg. of the potassium salt; or the same product is obtained by passing sulphurous anhydride to excess in a solution of the alkaline nitrate, containing also a carbonate or hydroxide. The resulting solutions being heated for a short time at 13o deg., or a longer period at loo deg., are resolved into hydroxylamine and alkaline sulphates, easily separable by fractional crystallization. It was recommended in 1884 by Messrs. Egli and Spiller as a developer claiming a wide latitude in exposure and permanency of the solution, unaffected by the air. Their formula runs as follows:

This developer will be found more suitable for chloride plates and bromide contact and enlarging papers.

The hydroxlamine is usually obtained by the reduction of nitric acid with tin and hydro chloric acid. Chapman Jones says* that a simple solution of this salt appears to be useless as a developer, and the addition of ammonia or sodium carbonate makes but little difference; with caustic potash or caustic soda, however, a solution can be prepared that will give as much detail as an ordinary pyrogallic developer.

In the production of the image the chemical changes that in all probability takes place are thus expressed : sNH2OHC1 + 6NaOH + 4AgBr = 4Ag + 4NaBr + 2NaC1 + + One of the principal drawbacks to this developer, besides its expensiveness, is its peculiar expanding action upon the gelatine film, causing frilling.