Mercury rectifiers were invented in 1902 by American electrical engineer Peter Cooper Hewitt. A rectifier is a device that converts Alternating Current (AC), which periodically changes direction, into Direct Current (DC), which travels only in one direction. AC is a much better means for distributing electrical power over long distances, but almost everything that runs on electricity requires DC to operate, and Hewitt’s invention was the first that could “rectify” AC in to DC without highly inefficient mechanical processes. Their use was widespread, powering everything from trains, trolleys, lighting systems, industrial motors, and more. In the 1970s, they were phased out in favor of semiconductor rectifiers. Only a handful are still in use today.
There were no labels or property tags related to its use at Rice, and no one at the Woodson knows what the ‘Y4C’ on the little brown tag means. The number on the glass envelope appears in a General Electric catalog from 1913. This model appears to have been used for charging batteries.
That’s real mercury in there, but never fear! Despite its age, this rectifier is still safe to handle.
by Jeff Warner