Calcium phosphide

• Phosphorus calcium
• Tricalciumdiphosphid
• Calcium phosphide

Malodorous ( " after carbide " ), flammable, brown-red amorphous mass

Fixed

2.51 g · cm -3

~ 1600 ° C

Soluble with decomposition in water

Risk

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Occurrence

Calcium phosphide found as a contaminant present in calcium carbide.

Production and representation

Calcium phosphide can be prepared by reaction of burnt lime with the vaporous phosphorus. Also during the melting of phosphorus with calcium under petroleum or vacuum formed calcium phosphide.

In addition, the reduction of calcium phosphate to calcium phosphide with carbon at high temperatures is possible ( side reaction in the calcium carbide ).

In the reaction, the substitution of carbon by aluminum is possible.

Properties

Calcium phosphide is a red-brown solid. In moist air it decomposes slowly with water to calcium hydroxide and lively monophosphane. Concentrated acids attack calcium phosphide in contrast to the dilute acids especially in the cold, almost not at all. With potassium permanganate calcium phosphide reacts explosively. Anhydrous alcohol, ether and benzene do not react at ordinary temperatures with calcium phosphide.

Use

Calcium phosphide can be used for the production of phosphine:

It is used against voles in this sense, as a fumigant ( rodenticide ).

Main field of application: For pest control in grain storage and grain shipments (eg ships), the grain is mixed with calcium phosphide tablets. The residual moisture of the grain is sufficient to hydrolyze the calcium phosphide then gradually, with phosphine is free, grain beetles and other pests kills reliably.

In the Navy, this reaction is used ( by formation of diphosphine Autoignition ) for operation of beacons.

Safety

Calcium phosphide is formed upon contact with water or damp air, evolve highly flammable gases in the form of toxic and malodorous phosphine PH3 and diphosphine ( P2H4 ). The gaseous mixture of phosphine PH3/Diphosphin can with external ignition - similar oxyhydrogen - decompose explosively.

On contact with acids explosive decomposition is possible. In the hydrolysis produced a very toxic for humans gas mixture ( phosphine PH3 and diphosphine P2H4 ). In mills and grain stores, there were already several times by misapplication of calcium phosphide and seal or lack of ventilation deaths.