Arsenic

Metalloid with steel-gray, metallic color.

SymbolAs
Atomic number33
Atomic weight74.91
Specific weight at 20 °C5.7 g/cm3
Melting point814 °C
Boiling point610 °C
Melting heat370 kJ/kg
Specific thermal capacity at 20 °C0.33 kJ/(kg·K)
Thermal conductivity370 kJ/(m·K)
Therm. coefficient for linear expansion4.7·10-6/K

At atmospheric pressure, arsenic does not get to the point of melting, since the vapor pressure of solid arsenic is already 1 bar at a temperature of 610 °C; at this temperature, arsenic undergoes sublimation. The element and its compounds are highly poisonous. The working materials regulation prohibits unrestricted use.

Arsenic in steel
At 830 °C iron may contain up to 7 % As in solid solution, predominantly in the form of iron arsenide (FeAs2). In alloyed steels with rather high nickel and chromium contents, aresenides of these metals may be formed. In the presence of cementite, ternery aresenide carbide eutectics are formed.

Arsenic in cast iron
Various types of pig iron may contain up to 0.01 % As. These arsenic quantities have a strongly perlite-stabilizing effect on the structure, with increasing tensile strength and hardness but decreasing elongation at failure. Today, addition of metallic arsenic to nodular graphite cast iron is no longer a possibility.

 

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