Fun with mercury

In recent years, mercury has required a bad reputation as a toxic chemical that one should avoid. Back in the day when I was a schoolboy, mercury was the element that was the most fun. We would handle it with bare hands in science classes to measure atmospheric pressure and rejoice when a mercury thermometer broke and we could play with this fascinating liquid metal and its strange properties that would try to form itself into a sphere if possible and would slide over surfaces so easily.

In this video from Cody’s Lab, Cody has about 350 pounds of mercury at his disposal and he looks at what happens when he tries to stand in a vat containing the liquid. In theory he should float because the density of mercury is 13.6 times that of water and that of the human body is almost the same as that of water. So floating is easy but staying upright is hard because you only sink as far as slightly above your ankles and this makes you highly unstable.

Watch Cody try his best.


  1. John Morales says

    Hm. Mercury has a very low vapor pressure if cool (I notice he mentioned it was at around -1C), but it is rather effectively absorbed by the lungs.

  2. jazzlet says

    When Cody was talking about floating a battleship on a glass of water I remembered a wonderful piece of … I suppose art, that is in a square in Bracknell. It’s a polished ball of granite may be six foot across set in a polished bowl of granite with water pumped up from the bottom of the bowl so it genty overflows. The ball floats and you can spin it with just a light touch, after playing with it for a while we went to a pub at the edge of the square and watched as all sorts of people went out of their way to play with it. Great fun!

  3. says


    I still have a vial of mercury that I inherited from my paternal grandfather. (His older brother, my Uncle Frederick, was a dentist and my grandfather—who had an 8th grade education—did a lot of his lab work in the teens and twenties.)

    When I was about eight or so, my grandfather put a tiny amount of the metal on a silver quarter. The mercury quickly covered the the whole coin and gave the quarter a slippery feel.

    Today he’d be locked up for endangering the health of a child, I suppose.


  4. VolcanoMan says

    Yup, not exactly “safe” but as a frequent viewer of Cody and his experiments, it’s not only not the most dangerous thing he’s ever done (not by a long shot) but he’s actually gotten blood tested for mercury at least once (and made a video about it of course) after having played with a LOT of Hg*; the test found normal levels, not even slightly elevated. Let’s see what else he’s done that is not exactly safe:

    1) Drink a sodium cyanide solution of concentration well below LD50 levels (although he did ingest enough CN- to notice slight hypoxia). YouTube age-restricted that video, for obvious reasons, but it was a nice demonstration of the “everything is poisonous/safe at the right dose” concept (while there are some substances that are considered bad at any dose because of bioaccumulative effects, NaCN isn’t one of them).

    2) Blow stuff up. He made a bomb to commemorate his channel’s 500,000th subscriber. A copper (II) thermite bomb (for those in the know, Cu thermites can be classed as low explosives because the temperature of reaction exceeds the boiling point of copper, and the expansion of copper from liquid to gas is quite fast and dramatic).

    3) Blow more stuff up. He tested one element of the idea (ideal for a show like Mythbusters actually) that the US may have inadvertently beaten the Soviets to putting an object into orbit during one of their early nuclear tests, when a manhole-cover-like flat cylinder was blasted out of a shaft during the (underground) test due to the pressure wave (the high-speed imagery the US scientists took showed it in one frame immediately after the explosion, but it was gone the next, and the frame-rates on the cameras capturing nuclear detonations were pretty insane). The idea is that if it stayed flat, air-resistance would probably stop it after a few kilometers, while if it deformed into a convex shape, it would be more aerodynamic and would have enough energy to leave the atmosphere. Using ANFO, he did a small-scale experiment which showed that the setup of the explosion would have resulted in higher pressure hitting the middle of the metal cylinder than the outside, resulting in deformation that would have made it more likely to travel farther, perhaps even into outer space. It’s by no means proof, but it adds credibility to the story.

    4) He tested Avogadro’s limit by diluting the fairly toxic mercury nitrate over and over again until you could only describe the concentration probabilistically (i.e. there’s a 10% chance that a solution contains one atom of Hg++). Obviously the water he drank to prove its safety was safe to drink, but it was also a neat demonstration of the idiocy of homeopathy, since he’d theoretically made a compound that homeopaths would call powerful medicine. Still, playing with ionic mercury isn’t really safe – that stuff is extremely bioavailable and should be avoided at all costs.

    5) He used lithium metal to reduce cesium chloride to cesium metal, and then made a YouTube play button out of the cesium (easily 250 grams of it). Cesium, for non-chemistry nuts, is a highly explosive, gold-colored metal that melts barely above room temperature; even leaving it exposed to air for a couple seconds will cause it to ignite (it reacts with water, even water vapor, violently). Having that much in one place is a recipe for disaster, but he chucked it into a large pond to blow it up and safely deal with it at the same time.

    6) Blow even more stuff up. He plays with nitroglycerine a lot. And he routinely makes his own black powder (and fires weapons with it, including homemade weapons like cannons). Once, he used his own urine to make KNO3, which was pure enough to make decent black powder. And he made nitrocellulose (gun cotton) out of an old pair of underpants.

    I will note that he treats the chemicals with the respect they deserve and I’ve only seen him hurt himself once through apparent carelessness (flicking a small amount of nitroglycerine with the tip of a knife caused the knife to shatter and a piece of it pierced his fingernail), but even there, he was wearing thick gloves and eye protection, so he was protected from the worst of it. A lot of commenters keep expecting him to blow himself up sometime (a fact he made fun of in a slightly inappropriate April Fool’s video that left relatives frantically calling his parents to find out if he was really dead), but he does generally have the knowledge to keep himself safe, and he does stress in videos that while he can’t stop anyone from copying him, he recommends they refrain from doing so.

    Fun stuff; I recommend watching his videos since they’re all entertaining, educational and sometimes explosive.

    *He did several experiments including answering a) “can Hg be flushed down a toilet* with water under normal conditions?” (answer = partially) and b) “can you make a toilet flush with ONLY Hg in the upper and lower tanks?” (answer = yes if you manually raise the stopper in the upper tank because the chain connected to the lever is not strong enough to work against the weight of the Hg). These experiments were conducted under closed-system conditions obviously – no mercury was actually flushed into a sewer system. He set up his toilet to flush into a basin, and had the whole setup in a large, almost swimming-pool like container to stop spills from getting into the environment. Sure, some Hg certainly ended up in the air meaning it wasn’t a completely closed-system, but for an appreciable amount of Hg to evaporate, it would take days at subalpine Utah temperatures.

  5. says

    Yup, for many years now I have blamed those big, enticing bottles of Mercury on every one of my high school Physics Lab benches for the fact that I don’t rival Einstein*.
    * or for that matter surpass him.

  6. Reginald Selkirk says

    JAMuse: The Johnson Museum Turns 40

    The course of construction went smoothly save for one discovery: When crews broke through to the basement of the old Morse Hall, they discovered thirty pounds of mercury near an old drainage pipe, a remnant from the chemistry building in the 1920s. Safe removal of the mercury delayed progress for several weeks.

  7. jazzlet says

    chigau #3
    Thank you I’d no idea they were so widespread or that the proper name was kugel fountain.

    VolcanoMan #5
    I don’t know about mercury, but I know getting the barium from a barium meal to flush away is difficult. Of course you are trying to flush it away with water, then when you realise that won’t work brush it away with a toilet brush while also flushing.

  8. VolcanoMan says

    @Reginald Selkirk

    30 lbs of Hg sounds like a lot, but volumetrically it’s only about a liter. You can check my math if you want, I know it sounds like a ridiculously small amount, but I’m pretty sure I did the calculation correctly.

    30 lbs * 454 g/lb = 13,620 g = 13.620 kg
    Density of Hg = 13.534 kg/L

    Dividing one by the other gives you about 1006 mL.

    To put that into perspective, when Cody did the toilet experiment, he used about 300 lb of Hg, or 10 L, which is enough to fill an old-style toilet (i.e. non-water efficient) reservoir tank to the brim. I was actually shocked that the porcelain withstood the pressure of that much mass pressing on the sides, but it held, and lifting the valve manually sent discrete streams of Hg running into the bowl, creating an effect that I can only say looked like I imagine a 50-legged spider would look. It was pretty badass, although I don’t want to think about how hard it was to clean up, and later to re-distill all of that mercury (and he did say he was planning on re-distilling it all since he also tried – successfully – to flush a small bar, maybe 4-6 oz, of 24-carat gold with the pure mercury flush, and some of the gold would have dissolved into the Hg; he wanted to recover this gold, and the only way is evaporation and condensation of the entire load of mercury).


    Interesting; is the lingering effect primarily due to the mass of the barium sulfate salt, or its adhesive properties when combined with the porcelain bowl? I’d imagine it’s the latter since BaSO4 has a density of just 4.5 g/cm3. For comparison, lead bullets are hard to flush down a toilet but the density of lead is 2.5 times that of BaSO4. Flushing powdered hematite (iron (III) oxide, a form of rust) would be analogous to flushing BaSO4 (actually, hematite is a bit denser still) – if hematite flushes no problem (since it shouldn’t interact with the toilet bowl at all, its density would be the only thing to prevent flushing), then the barium salt must have other properties that make it hard to flush.

  9. says

    I’ve seen it in science classes but was never allowed to touch it. One of the dangers most people don’t realize is that it leaves traces behind, even if it does adhere to itself. Many think it behaves like magnets.

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