Calcium hydride

This grey powder (white if pure, which is rare) reacts vigorously with water, liberating hydrogen gas.

The compound has, however, been widely used for decades as a safe and convenient means to inflate weather balloons.

Likewise, it is regularly used in laboratories to produce small quantities of highly pure hydrogen for experiments.

[4] The reaction of CaH2 with water can be represented as follows: The two hydrolysis products, gaseous H2 and Ca(OH)2, are readily separated from the dried solvent.

[2] Despite its convenience, CaH2 has a few drawbacks: During the Battle of the Atlantic, German submarines used calcium hydride as a sonar decoy called bold.

Calcium hydride
Calcium hydride
NFPA 704 four-colored diamond Health 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gas Flammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasoline Instability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorus Special hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid