An ammonium-salt fertilizer pile explosion killed hundreds in 1921

Evidence

On September 21, 1921, a silo storing 4500 tons of a mixture of ammonium sulfate and ammonium nitrate fertilizer exploded at a BASF plant in Oppau, now part of Ludwigshafen, Germany. It was not known that this mixture was explosive. Dynamite was used to loosen the fertilizer, which becomes clumped because it is hygroscopic (attracts moisture). Apparently, the dynamite had worked thousands of times without mishap, but not this time. The 20-meter-high pile exploded, killing 400 to 600 people—the equivalent of one or two thousand tons of TNT. More than 25,000 people were left homeless. — Eric J. Heller, Why You Hear What You Hear- An…, 2604