thumb | right | Armstrong’s Mixture
Armstrong's mixture is a highly shock and friction sensitive explosive. Formulations vary, but one consists of 67% potassium chlorate, 27% red phosphorus, 3% sulfur, and 3% calcium carbonate. It is named for Sir William Armstrong, who invented it sometime prior to 1872 for use in explosive shells.
Toys
Armstrong's mixture can be used as ammunition for toy cap guns. The mixture is suspended in water with some gum arabic or similar binder and deposited in drops, each containing a few milligrams of explosive, to dry between layers of paper backing. The dots explode with some smoke when struck. This use as primer for artillery propellants may have been Armstrong's original purpose.
It also was seen in various patents for matches, novelty fireworks, and signalling devices. Such toy caps and fireworks typically contain no more than 10 milligrams each, but gram quantities can cause maiming hand injuries.
The mixture is likely to explode if mixed dry and is even dangerous wet. If the pH is not made neutral, phosphoric acids that may have been generated by oxidized phosphorus on contact with the water could cause it to deteriorate while slowly drying. Generally the wet slurry or paste is loaded into the final casing while wet and was heat-dried in rotating drums prior to being coated with water glass to securely protect them from leakage when globe torpedoes were still in production commercially.