Product Identity and Properties
Hydroxylamine hydrochloride (CAS 5470-11-1), also written hydroxylamine HCl, is the salt formed from hydroxylamine and hydrochloric acid, with the formula NH2OH.HCl and a molar mass of 69.49 g/mol. It is a colourless to white crystalline solid, very soluble in water, and it gives acidic solutions. On heating it softens and decomposes in the region of 150 C rather than melting cleanly, releasing nitrogen oxides and hydrogen chloride, so drying and thermal operations must be controlled carefully.
| Property | Value |
|---|---|
| Chemical name | hydroxylamine hydrochloride |
| CAS number | 5470-11-1 |
| Molecular formula | NH2OH.HCl |
| Molar mass | 69.49 g/mol |
| Appearance | colourless to white crystalline solid |
| Thermal behaviour | decomposes around 150 C |
| Density | about 1.67 g/cm3 |
| Solubility in water | high; solutions are acidic |
Chemical Behaviour and Main Reaction Routes
The compound is a strong reducing agent and a versatile source of the hydroxylamine group. Its most common industrial reaction is with aldehydes and ketones to form oximes, a step used to protect carbonyl groups and to produce intermediates for further synthesis. With acyl chlorides, esters or acid anhydrides it forms hydroxamic acids, and with metal ions it acts as a reducing agent, converting for example ferric salts to the ferrous state. Aqueous solutions are acidic and attack many metals, so glass-lined, plastic-lined or stainless steel equipment is used in handling. Because hydroxylamine and its salts can decompose exothermically when concentrated or heated, process safety studies look closely at pH, temperature and the presence of oxidising agents.
Uses in Pharmaceuticals and Agrochemicals
Hydroxylamine hydrochloride is a standard reagent in fine chemical manufacturing. It is used in the synthesis of oxime intermediates for active pharmaceutical ingredients, in the preparation of hydroxamic acid derivatives, and in the production of pesticides, herbicides and fungicides where an oxime or hydroxylamine function is required. In the caprolactam chain, cyclohexanone oxime is a key intermediate, and hydroxylamine chemistry is one of the routes to it. Because the reagent is water-soluble, reactions are often run in aqueous or aqueous-alcoholic media, which simplifies work-up and reduces solvent consumption compared with organic-phase alternatives.
Uses in Metals, Polymers and Water Treatment
Outside fine chemicals, the salt is used as a flotation reagent in mineral processing, where it modifies the surface of certain ores and improves selectivity. It serves as a corrosion inhibitor in some closed-loop systems, as an oxygen scavenger in boiler water treatment, and as a short-stop or polymerisation inhibitor in the manufacture of unsaturated monomers, where it terminates radical chains. In photographic processing it acts as a reducing component of developer formulations, and it is used as an antioxidant in laboratory and industrial preparation of sensitive compounds. Each of these uses exploits either its reducing power or its ability to bind and convert metal ions.
Handling, Storage and Quality Control
Hydroxylamine hydrochloride is harmful if swallowed or in contact with skin and is a skin sensitiser; it causes serious eye damage. The label therefore shows the exclamation mark together with the corrosion pictogram for eye effects. Workers should use chemical goggles or a face shield, gloves of a verified material, and respiratory protection where dust is generated, and all operations should be carried out with local exhaust ventilation. The solid must be kept away from oxidising agents, strong bases and heat, and stored in closed, labelled containers in a cool, dry, well-ventilated area. Quality control for commercial grades normally includes assay by oxidation-reduction titration, water content, residue on ignition, iron and heavy metals, and clarity of the aqueous solution. Buyers with pharmaceutical interest will additionally require a related-substances profile and a residual solvents statement. Grades are typically offered as technical, industrial and pharmaceutical intermediate qualities, in 25 kg fibre drums with an inner polyethylene liner.
Frequently Asked Questions
Q: What is hydroxylamine hydrochloride used for?
A: It is a reducing agent and a source of the hydroxylamine group, used to make oximes and hydroxamic acids, as an intermediate in pharmaceuticals and agrochemicals, in metal flotation, in boiler water treatment and in photographic developers.
Q: Is the substance hazardous?
A: Yes. It is harmful if swallowed or in contact with skin, it is a skin sensitiser, and it can cause serious eye damage, so eye protection, gloves and ventilation are required when handling it.
Q: How should hydroxylamine hydrochloride be stored?
A: In closed containers in a cool, dry, ventilated place away from oxidising agents, strong bases and heat sources, since heating or contact with oxidisers can lead to exothermic decomposition.
Q: Why is it supplied as the hydrochloride rather than as free hydroxylamine?
A: The free base is unstable and volatile, while the hydrochloride is a stable crystalline solid that dissolves readily in water and releases the hydroxylamine group in the reaction medium.
Q: Which methods are used to test commercial grades?
A: Assay by oxidation-reduction titration, water content, residue on ignition, iron and heavy metal limits, and clarity of the aqueous solution, with related substances and residual solvents added for pharmaceutical grades.
Q: What packaging is standard for export?
A: 25 kg fibre drums with an inner polyethylene liner, palletised and shrink-wrapped, with the appropriate hazard labelling and documentation for a harmful and corrosive material.