Mercury (Hg) is a liquid metal used in everyday life and technology as a working fluid for various measuring instruments and electrical position relays. Due to its unique properties, as well as the ease of obtaining in its pure form, mercury has become widespread. Around this metal, especially recently, a lot of conjectures and myths have appeared, based mostly on ignorance of school chemistry and physics, and not on the real properties of mercury.
Mercury is highly toxic. Even a broken medical thermometer can cause instant poisoning. Metallic mercury is just as poisonous as any other heavy metal (such as copper). In the Middle Ages, alchemists even took mercury internally as "medicinal" pills and, nevertheless, remained alive. It should be noted that when it enters the digestive system, it is metallic mercury that is relatively safe, and not its salts! The notorious "toxicity" is due to its vapors contained in the air. At a temperature of 18 ° C, intensive evaporation of mercury into the atmosphere begins, inhalation of such air contributes to its accumulation in the body from where it is no longer excreted (like other heavy metals). However, in order to accumulate a significant proportion of mercury in the body, it is necessary for several months or years to regularly stay indoors with a serious excess of the MPC for this metal in the air.
There is so little mercury in a medical thermometer that you can ignore it if you break it. A ball of mercury the size of a pinhead is enough for the concentration of mercury vapor in a medium-sized room with closed windows and working ventilation to exceed the MPC by hundreds, or even thousands of times (however, with intensive ventilation, the norm will be established almost immediately). Therefore, you should not neglect the spill of mercury even in small quantities.
You can prevent the evaporation of mercury by storing it under a layer of water. The solubility of mercury in water, although small, is much higher than the solubility of mercury in air. Therefore, it is obvious that mercury from an aqueous solution will still evaporate into the air.
The mercury balls can be collected with a vacuum cleaner. In no case should this be done. First, it is not very effective, since mercury has a very high density, and most vacuum cleaners simply cannot remove the balls from hard-to-reach places. Secondly, the air passing through the nozzles heats up, which leads to an even more intense evaporation of the mercury that has got into the bag, and the spread of these vapors throughout the volume of the room. In fact, a very efficient "vaporizer" of mercury is obtained from a vacuum cleaner. Thirdly, after such "processing" you will also have to throw out the vacuum cleaner.
Mercury can be poured down the drain (toilet, sink). By doing this, you will harm, first of all, yourself, since the mercury will simply remain at the bottom of the water seal (pipe bend), from where it will evaporate back into the apartment for years. It's best to just throw the collected mercury into a street trash can (not a garbage chute!).
Mercury is radioactive. Mercury has radioactive isotopes, but they, of course, are not used in the manufacture of household thermometers, and indeed in all cases where it is not necessary. But for some reason we regularly hear statements about the radiation hazard of mercury.
Mercury is expensive. The cost of mercury is in the same order of magnitude as that of other metals. The market price depends on the purity of the mercury offered and the volume of the supplied batch. Naturally, it is not available on free sale, since mercury belongs to hazardous chemicals (emergency chemical-hazardous toxic substances). In everyday life, in order for the mercury to be taken for disposal, you will also have to pay to the relevant organizations.
Mercury is collected using sophisticated means available only to specialists. Demercurization (collection of mercury) is carried out in two stages. First, all visible metallic mercury is removed mechanically (scooping, sweeping with a stiff brush, suction with a syringe or syringe, picking up balls on tape, etc.). Then a chemical surface treatment is carried out (if this surface cannot be removed by itself, like carpet or topsoil). Of a wide range of chemical demercurizers, ferric chloride (FeCl3, with which radio amateurs etch printed circuit boards), as well as a solution of potassium permanganate (potassium permanganate), but always with the addition of hydrochloric acid (HCl). Industrial-scale spills use sulfur to bind the mercury, converting the mercury to sulfide.
There are special solutions that completely "destroy" mercury. Any demercurization solution simply converts mercury from a metallic state to a bound one (usually in HgCl2 chloride). The volatility of mercury salts is much lower than the volatility in the free state, which is the basis of the effect of chemical treatment (therefore, it is always better to get rid of the contaminated surface than to treat it).