Strontium Arsenide, Sr3As2, may be prepared by the
reaction of the elements or by the reduction of strontium
arsenate. The latter method is best accomplished by
rapidly heating with carbon to 1500 to 1600 °C. If the
heating is slow, reduction begins at about 800 °C
yielding first the arsenite, arsenic then being lost and
strontium oxide formed:
3Sr + 2As + heat ? Sr3As2
2Sr3AsO4 + 4C + heat ? Sr3As2 + 3SrO + 3CO + CO2
Strontium arsenide forms reddish-brown crystals,
transparent in thin sections, with a density of 3.23 g/
cm3. It has the CAS number 39297-24-0. Its molecular
weight is 1167.9668 g/mol. It decomposes in contact
with water, forming strontium hydroxide with liberation
of arsine. It burns brilliantly when heated in oxygen or
sulfur vapor. It reacts with fluorine at room temperature
with incandescence and formation of arsenic trifluoride.
Similar reactions occur with chlorine at 160°C, with
bromine at 200 °C, and with iodine vapor at a higher
temperature. It is a powerful reducing agent and attacks
most metallic oxides and oxidizing agents.
It is considered as a “Dangerous Substance for the
Environment” and is prohibited in Europe by the EEC.
