Ammonium hypophosphite

Preparation

1. One-step method: This method involves the direct reaction of yellow phosphorus with ammonia. However, the reaction conditions are difficult to control, often resulting in the formation of ammonium hypophosphite as a byproduct. Furthermore, this method produces toxic PH3 gas, which is flammable in air and extremely dangerous.
2. Neutralization method: Passing ammonia gas into high-purity hypophosphite produces an ammonium hypophosphite solution, which is then evaporated and crystallized to obtain the final product. This method is more complex in its operational steps.
3. Adding ammonium carbonate, an ammonium salt containing an anion that can be precipitated by calcium ions, to a calcium hypophosphite solution produces an ammonium hypophosphite solution. This solution is then concentrated to obtain solid ammonium hypophosphite.

Chemical Properties

white crystals

Uses

As catalyst in polyamide manufacture.

General Description

White crystalline solid. Sinks and mixes with water.

Air & Water Reactions

Water soluble. Ammonium hypophosphite liberates spontaneously flammable phosphine at about 240°C [Mellor 8:880 1946-47].

Reactivity Profile

Ammonium hypophosphite liberates spontaneously flammable phosphine at about 240°C [Mellor 8:880 1946-47]. Some inorganic materials, such as hypophosphites, tend to form explosive mixtures with perchloric acid when hot [Analyst 84:215 1959].

Hazard

Evolves flammable and toxic fumes on heating.

Health Hazard

Non-toxic or low toxicity unless heated to decomposition (240°C).

Flammability and Explosibility

Not classified

Purification Methods

Crystallise it from hot EtOH.