Hazards of Phosphorus Compounds

Most of the crystalline and amorphous varieties of red phosphorus are usually considered to be non-toxic provided they are free from all traces of the white form above. 

Phosphoric acid is a colourless viscous liquid which, when concentrated, will cause bums to eyes or skin and severe internal irritation. Harmless when suitably diluted and non-toxic when life forms are in contact with reasonable (normal) quantities. Slightly bitter taste when pure. Polyphosphoric acids have roughly similar hazards. Food grades of H3PO4 must meet strict purity specifications (Chapter 12). 

The common form of laboratory and commerce, phosphorus pentoxide is a deliquescent white powder which reacts violently with water. Will cause severe bums. Hydrolyses to orthophosphoric acid. Other crystalline forms are polymers (P205) , which are somewhat less reactive, but all forms eventually produce orthophosphoric acid on hydrolysis. 

Phosphine, PH3, is a colourless gas with characteristic rotting-fish smell. Slightly soluble in water and usually spontaneously inflammable in air due to traces of diphosphine, P2H4. 

Extremely toxic at 10 ppm and can be rapidly fatal at 2000 ppm. Some compounds such as phosphonium salts emit phosphine on heating, and some metal phosphides do likewise when in contact with moisture. 

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