What is the decomposition temperature and residue of sodium hypophosphite?

Sodium hypophosphite is a common chemical, not a hazardous chemical. It is relatively stable at room temperature, with a decomposition temperature generally around 200℃. The decomposition products are complex, and the sodium hypophosphite content and impurities vary. The decomposition residues vary at different temperatures and stages of decomposition. There are no special storage requirements; just keep the warehouse dry and cool, and store away from other chemicals, especially strong oxidizers. Below is a brief introduction from several aspects.

Decomposition Stage:

Sodium hypophosphite begins to decompose when the ambient temperature exceeds 200℃. At this point, phosphorus (+1) begins to convert to phosphorus (+3), decomposing into sodium phosphite, sodium hydrogen phosphite, and phosphine (PH3). The reaction equation is: 3 NaH2PO2 (heated) ---- Na2HPO3 + NaH2PO3 + PH3↑

Therefore, store away from sources of fire and high temperatures.

Second Decomposition Stage:

Sodium phosphite and sodium hydrogen phosphite decompose into sodium phosphate and phosphine. Trivalent phosphorus is then gradually oxidized to pentavalent phosphorus, using the reaction equation: 3Na2HPO3----2Na3PO4+PH3↑. The first and second decomposition stages may occur simultaneously under conditions of sufficient oxygen and a rapid temperature increase. Decomposition does not necessarily follow the order described above.

The decomposition temperature of sodium hypophosphite is related to its purity. Decomposition products of varying purities exhibit varying thermal stability and thermal conductivity. Generally speaking, a higher content of other metal ions results in a lower decomposition temperature, primarily due to the thermal catalytic effect of some metal ions. High-content, high-purity sodium hypophosphite exhibits strong intermolecular crystalline interactions, resulting in melting upon heating. This results in improved thermal stability and a higher decomposition temperature. For every 5% decrease in the effective content, the decomposition temperature decreases by approximately 15℃.