Solution :
Holme's signal uses calcium carbide and calcium phosphide. The spontaneous combustion of phosphine is technically used in Holme's signals. Containers containing a mixture of calcium carbide and calcium phosphide are pierced and thrown in the sea when the gases burn and serve as a Signal.
Releted MCQ Question on Inorganic Chemistry >> P - Block Elements
Releted Question 1
The reddish brown coloured gas formed when nitric oxide is oxidised by air is