Yes it was. when people where transported to the Concentration camps the SS officers would spread quicklime on the floors of the carts burning the skin on contact. There was nothing to soothe the...
If limestone is heated strongly, it breaks down to form calcium oxide and carbon dioxide. Calcium oxide is also called quicklime. It is yellow when hot, but white when cold.
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Canisters were dropped into rooms to gas jews, it sometimes even came from the shower heads. (and it was also still used for its original purpose as a pesticide)