Mercury has been dropped on my floor and I want to collect it back in container. What is the best and easiest way to pick up mercury drops from the floor?
Mercury cleanup is not simple or easy. Though you can pick up the biggest droplets with a pipette (medicine dropper), do not use a vacuum cleaner, because it spreads the highly toxic mercury vapor throughout a room, or even a building.
The New York Department of Health has an online guide. In particular, after removing all droplets you can find, then rub powdered sulfur in the area of the spill, which will, over time, combine with mercury to form the less toxic mercury sulfide. The guide also lists sources for cleanup kits; Amazon carries a few for US$30 and more. A guide may also be downloaded from the US CDC.
The biggest danger is from long-term exposure to mercury vapor, or to organic mercury compounds that could be formed through bacterial action. Commercial hazardous waste specialists have meters to detect minuscule amounts of mercury vapor which can help track remaining particles in flooring. If the spill is large, definitely use professional cleanup service.
To collect bulk amounts a thin sheet of paper can be used. Lay the paper on the surface, then use another piece of paper to coax the blob of mercury onto the paper. Once the blob is in the center of the paper, make a thick ring of glue around it and put a second sheet of paper on top and let it dry. The mercury will be trapped. Take the envelope to the container and puncture a hole through it, allowing the mercury to flow back into the container.
Note that the mercury will now be "dirty" and useless for many purposes because it will have absorbed dust and dirt. For this reason, spilled mercury is not usually re-used.
Whether you collect a blob or not, you still need to clean the surface where it dropped, because the mercury will be in the crevices.
Use a copper or brass wire brush of the thinest gage you can find. Jewelry supply houses (and Amazon) have fine brass wire brushes. Also, you can find copper "scourers" that are useful if the surface has no crevices. You can even use steel wool in crevices. If you use steel wool, I would recommend etching it first in vinegar. Soak the steel wool in vinegar for about an hour. Rinse and dry. Then use it on the mercury gently.
You can also make a brush. Get the finest copper wires you can find (by stripping braided electrical wire for example), then fold the wires over and over, then cut. Glue the wires to a little piece of wood or something so you have a brush. Now carefully brush all the places where the mercury was. The mercury will amalgamate into the copper. As long as the copper touches it, the mercury will flow into the copper perfectly and every last microgram will be absorbed.
Discard the brush in a well-sealed container.
Note: a good copper wire brush can also be used to collect blobs of spilled mercury as an alternative to the paper method; if your brush is good, the mercury will glom onto it in globules and can be shaken off into a container. In the old days, this was the standard method to recover significant quantities of spilled mercury.