The chemials used in Holme’s signals are

Holmes signal is a chemical mixture commonly used as a signal for ships in the sea, especially when visibility is poor or in emergency situations. The chemicals involved in Holmes signal are calcium carbide (CaC2) and calcium phosphide (Ca3P2). When these substances come into contact with water, they undergo chemical reactions that produce two highly flammable gases: phosphine (PH3) and acetylene (C2H2).

Here’s a breakdown of the reaction:

• Calcium carbide reacts with water to form acetylene gas (C2H2) and calcium hydroxide (Ca(OH)2).
• Calcium phosphide reacts with water to form phosphine gas (PH3) and calcium hydroxide (Ca(OH)2).

The acetylene and phosphine gases that are produced are both highly flammable and, when ignited, burn with a bright flame. This combustion helps to guide ships through dark or foggy waters. The reaction is simple but highly effective for maritime navigation under challenging conditions, particularly in low visibility areas such as fog or during night time.

Thus, this mixture of calcium carbide and calcium phosphide serves as an important signaling tool for ships, especially in emergency situations or when traditional signals like lights are not available.