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Mercury in a vacuum

Posted by Conservators on Feb 4, 2014 10:40:05 PM

Author: Josiah Wagener

Date: 05/02/14

Temperature: -2C

Sunrise: None. It's up all the time

Sunset: 20 February 2014

 


This summer I spent several days conserving the Fleuss vacuum pump found on the bench in the science corner of the Cape Evans hut. This is a hand powered single cylinder vacuum pump made of cast iron and cast brass.
Pump before treatment (Small).JPG

Fleuss vacuum pump before treatment © AHT/Josiah Wagener


The pump would most likely have been used for drawing a vacuum in a bell jar in order to run chemical experiments at 0 pressure, or to draw chemicals through a filter system for experiments. It was made by the Pulsometer Engineering Co. of Reading, England, from a design patented by Henri Fleuss who was famous for inventing self contained diving apparatus in the late 19th century. He called this model the Geryk after the German scientist who invented the general style of vacuum pump in the 17th century.
Makers plate (Small).JPG

Makers plate © AHT/Josiah Wagener

 


The pump was heavily corroded, having been exposed to over a century of high humidity and regular freeze/thaw cycles. Most of the ironwork had been painted black at one time and part of the vacuum bulb and the pump cylinder had been painted red, however, only flaking traces of the paint remained.
Pump after treatment (Small).JPG

Fleuss vacuum pump after treatment © AHT/Josiah Wagener

 

Remnants of mercury in the bottom of the bulb and the valve chamber of the pump has resulted in chemical degradation amalgamation leaving some of the metal porous and crumbly. We are unsure of the purpose of the mercury, and would be interested in any knowledge our readers can give us as to its purpose within the pump.


One unfortunate side effect of contact with mercury is that the solder and brass of the vacuum bulb has become very fragile and has cracked around the base.
Cracked bulb (Small).JPG

Cracked bulb © AHT/Josiah Wagener


To conserve the item, the rust was reduced with hand tools and abrasive pads then the remaining rust was converted with a tannic acid solution. The resulting dark surface was coated first with acrylic lacquer and then with microcrystalline wax. A brass rod splint was fashioned to hold the cracked bulb in place.


The treated pump will resume its place on the end of the science bench, now stable and protected for many more years.
Pump on workbench (Small).JPG

Fleuss vacuum pump on workbench © AHT/Josiah Wagener

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