Mercury ??

RichB

Senior Member
Location
Tacoma, Wa
When I was in third grade some kid brought in a mercury switch which he said that he got from the furnace at home :rolleyes:.
It was just like the one pictured below. We were all passing it between each other, and then there was a crash and the mercury spread out across the floor in many tiny droplets. The teacher's solution was to hand out index cards to the kids, and we all crouched down trying to round up all the little droplets and gather them to together into one big blob. I don't remember what happened then, but the teacher probably just tossed it into the local garbage pail and that was that.
View attachment 2552290
Nowadays I'm sure they'd call in a hazmat team and close the whole school to do a remediation/cleanup.
While in the shipyard in Bremerton in 82 we had a yardbird drop a fluorescent tube--old t12 48 inch, all the yard birds walked out. about 30 minutes later in walks a hazmat clean up team in full gear--those of us that had the watch just sat there and observed thinking " it's just a tube --whats the big deal".

I always told our new guys that the reason we no longer broke the old tubes against the side of the boat was that, since fluorescent lighting worked like refrigeration--doesn't put out cold removes heat, they don't put out light but removes dark-ons, is because the environmentalists got after us because it let the dark ons out and the fish couldn't see to eat or escape predators:rolleyes:
 

paulengr

Senior Member
But the mercury vapor pressure is very low at room temperature, so it isn't the high risk some people believe. If you left a small drop on the back shelf I'll bet that in 50 years you couldn't tell the difference, and could only weight it with precision scales.
Back in the day when they used it to separate gold, and then burned it off, that was a different story.
This is correct. Mercury is not absorbed through the skin. Mercury is basically harmless. Until you vaporize it. Even then it’s not nearly as bad as a lot of mercury compounds (nitrates) that are easily absorbed through the lungs and straight into the blood stream. It isn’t recognized by the body so it accumulates over time.

Quicksilver is an old name because that’s what it looks like.

They did not burn off the mercury. That would be stupidly expensive and inefficient. Plus mercury does not burn. Whoever told you that knows nothing about metallurgy. Take it from a metallurgist. There is an early crusher/grinder called a stamp mill and mercury was used to capture the loose gold particles in a process called mercury amalgamation. Harmless to people.


This fell out of favor around a hundred years ago as stamp mills are horrible in terms of energy efficiency. For true grinding it went to crushers followed by rod/ball mills but today many mines are converting to SAG or fully autogenous mills or high pressure roll crushers where rocks grind rocks.

In modern gold making though we don’t even grind usually. First we crush only. Then we dissolve the gold (effective down to about 1 gram per ton) with cyanide solution either in piles (heap leaching) or large vats (Pachuca tanks). Then we strip the cyanide with activated carbon (older process uses zinc). At this point the cyanide gets reused 100%. This sounds dangerous but as long as the pH stays high the cyanide stays in solution and is harmless. Bleach easily destroys it if needed. The carbon can either be burned or hot acid washed to strip the gold off the carbon. The wash solution if used is evaporated to release gold or it can be separated by electrolysis.

What was not so harmless was felt making. They would treat hair from beaver or rabbits with mercury nitrate. Once treated they would pack the hair into felt then dry it in an oven. The mercury nitrate fumes caused Erethism aka mad hatter disease.
 
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