Phosphine (PH3) is used in Holme’s signals in deep seas and oceans for signalling danger points to steamers. Containers containing a mixture of calcium phosphide and calcium carbide are pierced and thrown into the sea.
In contact with water, a mixture of acetylene and phosphine is produced. Phosphine contains traces of highly inflammable P2H4 which catches five spontaneously. This ignites acetylene with a luminous flame and thus serves as a signal to the approaching ship.
