Phosphorus is involved in the ignition of matches, but the type used and its location have changed dramatically since matches were first invented due to safety concerns. Modern match technology has evolved into two distinct categories, each using different phosphorus compounds to achieve a controlled flame. This evolution involved replacing highly reactive and toxic chemicals with more stable alternatives.
The Toxic Legacy of Early White Phosphorus Matches
The earliest reliable friction matches, popular in the 19th century, relied on white phosphorus. This highly reactive chemical was mixed into the match head because its low ignition temperature allowed the match to be lit easily on any rough surface. This made “strike-anywhere” matches commercially successful.
However, the use of white phosphorus caused a devastating occupational disease among factory workers. Exposure to the toxic vapor caused phosphorus necrosis of the jaw, or “phossy jaw.” This ailment progressed to severe necrosis of the jawbone, often requiring surgical removal.
The severe health hazards led to widespread public outcry and international regulation. Countries began banning the substance in the early 20th century. The International Berne Convention of 1906 prohibited the manufacture, importation, and sale of white phosphorus matches, forcing manufacturers to develop safer chemical alternatives.
How Modern “Strike Anywhere” Matches Ignite Without Head Phosphorus
The modern “strike anywhere” match contains all necessary ignition chemicals in the match head without using pure white or red phosphorus. Instead, the head typically contains a stable phosphorus compound called tetraphosphorus trisulfide (\(\text{P}_4\text{S}_3\)). This compound is significantly less volatile and toxic than white phosphorus, eliminating the associated health risks.
The match head is a complex mixture of components that work together when friction is applied:
- The oxidizer, often potassium chlorate (\(\text{KClO}_3\)), provides the oxygen necessary to sustain combustion.
- The fuel, such as sulfur or starch, ignites once the initial spark is generated.
- The friction agent, typically powdered glass, is embedded in the composition.
When the match is struck against a rough surface, the friction generates enough heat to decompose and ignite the phosphorus trisulfide. This rapid ignition is immediately fueled by the oxygen released from the potassium chlorate, causing the sulfur fuel to burn and establish the main flame.
The Segregated Role of Red Phosphorus in Safety Matches
The most common type of match, the safety match, differs from the strike-anywhere variety by physically separating the most reactive chemicals. The match head itself does not contain elemental phosphorus. It is composed of an oxidizer, such as potassium chlorate, along with a fuel like sulfur and an abrasive material.
The phosphorus component is isolated on the striking strip, typically located on the side of the matchbox. This strip contains the more stable allotrope, red phosphorus, mixed with a binder and a friction agent. Red phosphorus is non-toxic and has a much higher ignition temperature than white phosphorus, preventing accidental ignition.
When the match is rubbed against the striking surface, the friction generates heat. This heat causes red phosphorus to convert into highly reactive white phosphorus, which immediately ignites. This spontaneous ignition initiates a reaction with the potassium chlorate in the match head, igniting the sulfur fuel and creating a stable flame. This segregation ensures the match can only be lit when intentionally struck.