Sodium Hypophosphite: Calcium Hypophosphite and Soda

Sodium hypophosphite is the reducing agent of electroless nickel plating. US Dispensatory (1907): mix solutions of calcium hypophosphite and soda; chalk falls out and sodium hypophosphite stays in solution. Filter and evaporate. It has exploded when evaporated hot: keep it well below 100 °C, behind a face shield, and away from nitrates and chlorates. The picture: sodium hypophosphite crystals (Wikimedia Commons).