Halifax Explosion

Saturday, December 6th, 2014

On 6 December 1917, the largest man-made explosion in history (to that point) took place, not along the front lines of ongoing Great War, but in a Halifax, Nova Scotia:

The French ship Mont Blanc had just been loaded with a cargo of high explosive in New York: over five million pounds of explosives and inflammables, most of it highly unstable picric acid (Benzol, an octane booster then used in aviation fuel, and guncotton, a primitive explosive, were also aboard). Mont Blanc intended to join a convoy from Halifax to England, but on its way in to the harbor collided with an empty vessel, Imo, that normally ferried humanitarian aid to Belgium. Imo, with a Norwegian crew, was wrong-side-driving out of the harbor as Mont Blanc stood in, on the normal inbound side of the channel.

The crew and harbor pilot of Mont Blanc abandoned ship and fled when their hazardous cargo took fire; the ship drifted to land, drawing curious onlookers, then exploded. The city was devastated, especially the shoreline, the shipyards and docks, and other ships making ready for the next England convoys on the 7th and 11th (a single convoy would leave on the 11th).

Most of the convoy ships were in Bedford Basin, the most protected part of the harbor when Mont Blanc blew up in what locals call The Narrows. Fortunately, Mont Blanc was not near any of the other explosives-laden vessels when it went up.

At least 1,500 hundred lives were snuffed out in the blast and the following tsunami, and hundreds more died in the days ahead. Hundreds of remains were never identified. Some lasting results of the accident were standardization of fire hydrant and hose threads (responding fire departments found that the decimated Halifax department’s hydrants didn’t match their gear), more advance warning required for hazmat transits, and stricter maritime rules of the road in the harbor. There was a long series of saboteur hunts, enquiries, criminal trials, and private lawsuits, but in the end no one was singled out as solely to blame, or punished. It was a terrible accident, but in the end, just an accident.

Halifax Ground Zero

The manifest of the ill-starred Mont Blanc bares the spoor of the probable cause of the disaster — picric acid. This chemical was the first high explosive; its name comes from the Greek for “bitter.” Discovered and initially developed in the 18th Century, it became a dominant explosive and shell filling in the late 19th, when it was discovered initially by British scientist Sprengel. Picric acid was more powerful than the explosive that would come to replace it in most nations’ armories, TNT.

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Because unlike fairly stable TNT, picric acid and its salts — which form spontaneously on contact with common bases — are highly unstable; they tend to detonate when exposed to shock, friction, or flame. Picric acid corrodes metals and becomes more unstable in their presence, making it impossible to contain in metal cans or drums, and requiring special procedures for shell filling.

Before World War I, the German military had begun to shift to TNT. It was made by the same process that yields picric acid, just using a different feedstock; it’s only a little less explosive; and it’s vastly more stable. Over time all armies would follow suit, and fear of a repeat of the Halifax Explosion would be one reason (there were many other industrial and military accidents worldwide with picric acid that soured militaries on the chemical). Later, better HEs would be developed, both from the standpoint of stability and of energy, but it says something that TNT, which the Germans first put into shells in 1902, still is practically useful today.

The reason for going backwards in the power of explosive fillings was safety, and the far more stable TNT would have been unlikely to yield the Halifax Explosion. Even today, found Lyddite or Mélinite shells from WWI pose a threat.

Comments

  1. Grasspunk says:

    There’s a book, Aftermath, which has a section on the risky job of de-mining WWI battlefields in France. Not the safest of jobs. Luckily there are no WWI battlefields out here in the SW else I’d have to be a lot more careful when working the fields.

    Looks like they made a film about it, too.

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