Credit: Research paper, ACS Omega Building on this breakthrough, the scientists combined the acetate-based salt with various compounds including a surfactant, silicon dioxide, sodium bicarbonate ...

The liquid in the hand warmer is a very concentrated solution of a salt called sodium acetate. The sodium and acetate ions are ready to bond with each other and with water molecules to form a crystal.

A seed crystal can be dropped into a saturated solution of sodium acetate. The solution will suddenly crystallize and turn to solid. Alternately, the solution may be slowly poured out onto a seed ...

The first contains a fine iron powder, salt, and water in a pouch that is permeable to air. When it is exposed to air, the iron begins to rust. This rusting process produces heat. The second contains ...