At first, picric acid was used as a booster to detonate TNT, though it was superseded due to the inherent danger of picrate formation. Tetryl replaced picric acid because it is more stable, and was once a very popular chemical for booster charges, particularly during World War II. However, since then, tetryl has largely been replaced by other compositions, e.g. a small cylinder or pellet of phlegmatized RDX (e.g. CH-6 or Composition A-5) or PETN (slightly larger than the actual detonator) into which the detonator itself is inserted.
