Answer:
The poisoned substance was mixed with arsenic-free zinc and sulfuric acid, resulting in arsine gas.
The gas was later ignited and decomposed into pure metallic arsenic. This test was highly sensitive and could detect even one-fiftieth of a milligram of arsenic. It was a remarkable discovery, since before that, arsenic was widely used as poison in enormous amounts of murders, impossible to detect and trace.
The historians that came of age during the middle to late twentieth century tended to turn their attention toward : Social and cultural events and themes
This refer to the period between 1960 - 1999. many of them refer to the events that happen before this as 'history from below'
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The attack of the twin towers.
<span>swift rivers provided power for machines</span>