– These idiots placed a porcelain container with “jelly” in a special chamber, extremely isolated ... That is, they thought that the chamber was extremely isolated, but when they opened the container with manipulators, the “jelly” went through metal and plastic, like water through a blotter, escaped outside, and everything with which he came into contact, again turned into a "jelly". Thirty-five people died, more than a hundred were mutilated, and the entire building of the laboratory was brought into complete disrepair. Have you ever been there? Magnificent building! And now the “jelly” is stacked in the basements and lower floors ... Here is the prelude to contact.
- A. Strugatsky, B. Strugatsky "Roadside Picnic"
Hey %%username%!
The fact that I'm still writing something - blame . He came up with the idea.
It's just that, after some thought, I decided that a little digression into caustic substances would come out relatively quickly. Maybe someone will be interested. And for some it's useful.
Come on.
Let's define the terms right away.
Corrosive - 1. Chemically corrosive. 2. Sharp, causing irritation, pain. 3. Biting, caustic.
Ozhegov S.I. Dictionary of the Russian language. - M.: Rus.yaz., 1990. - 921 p.
So, we discard the last two meanings of the word at once. We also discard the "caustic" lachrymators - which are not so much caustic as they cause lacrimation, and sternites - which cause coughing. Yes, below there will be substances that have these properties, but they are the main thing! - do corrode materials, and sometimes flesh.
We will not consider substances that are caustic only for humans and the like - in view of the specific destruction of cell membranes. And therefore mustard gas will remain out of work.
We will consider compounds that are liquids at room conditions. Therefore, liquid oxygen and nitrogen, as well as gases such as fluorine, will not be considered, although they can be considered caustic, yes.
As usual, the view will be purely subjective, based on my own experience. And yes - it is quite possible that I won’t even mention someone - write comments,% username%, within three days from the date of publication, I will supplement the article with what was forgotten from the very beginning!
And yes - I don’t have the time and energy to build a hit parade, so there will be a hodgepodge. And with all the exceptions, it came out pretty short.
Caustic alkalis
Specifically, alkali metal hydroxides: lithium, sodium, potassium, rubidium, cesium, francium, thallium (I) hydroxide and barium hydroxide. But:
- We discard lithium, cesium, rubidium and barium - expensive and rare
- If you, %username%, come across francium hydroxide, then the causticity will be the last thing you care about - it is terribly radioactive
- The same with thallium - it is poisonous to horror.
That left sodium and potassium. But let's be honest - the properties of all caustic alkalis are very similar.
Sodium hydroxide - as "caustic soda" - is known to everyone. Potassium hydroxide as a food additive E525 - too. Both are similar in properties: they are highly hygroscopic, that is, they draw water, they “blur” in the air. They dissolve well in water, while a large amount of heat is released.
“Spreading” in air is, in fact, the formation of very concentrated solutions of alkalis. And therefore, if you put a piece of caustic alkali on paper, leather, some metals (the same aluminum), then after a while it turns out that the material has eaten up well! What was shown in the "Fight Club" is very similar to the truth: indeed, sweaty hands - yes, in alkali - it will hurt! Personally, it seemed to me more painful than from hydrochloric acid (more on that below).
However, if your hands are very dry, you most likely won’t feel anything in dry alkali.
Caustic alkalis perfectly break down fats into glycerin and salts of fatty acids - they cook soap (hello, “Fight Club!”) A little longer, but proteins break down just as effectively - that is, in principle, alkalis dissolve flesh, especially strong solutions - yes when heated . The disadvantage in comparison with the same perchloric acid (about it, too, below) is that all alkalis draw carbon dioxide from the atmosphere, and therefore the force will gradually decrease. In addition, alkalis also react with glass components - the glass becomes cloudy, although in order to dissolve it all - here, of course, you need to try.
Tetraalkylammonium hydroxides are sometimes referred to as caustic alkalis, for example
Tetramethylammonium hydroxide
In fact, these substances combined the properties of cationic surfactants (well, it’s like ordinary soap - only cationic: here the active particle is an amphiphilic particle with a “+” charge, and in soap with a “-” charge) and a relatively high basicity. If it gets on your hands, you can lather it in water and wash it like soap, if you warm your hair, skin or nails in an aqueous solution, they will dissolve. "Causticity" against the background of sodium and potassium hydroxides is so-so.
Sulfuric acid
H2SO4
Probably the most popular in all stories. Not the most caustic, but quite unpleasant: concentrated sulfuric acid (which is 98%) is an oily liquid that loves water very much, and therefore takes it away from everyone. Taking water away from cellulose and sugar, carbonizes them. In the same way, she will happily take water from you, %username%, especially if you pour it on the delicate skin of your face or in your eyes (well, everything will actually get into your eyes with adventures). Particularly kind people mix sulfuric acid with oil so that it is more difficult to wash off and better absorbed into the skin.
By the way, taking water, sulfuric acid warms up healthy, which makes the picture even more juicy. Therefore, washing it off with water is a very bad idea. Better - with oil (wash off, not rub - and then rinse with water). Well, or a large stream of water to immediately cool.
"First water, and then acid - otherwise a big disaster will happen!" - this is about sulfuric acid, although for some reason everyone thinks that about any acid.
Being an oxidizing agent, sulfuric acid oxidizes the surface of metals to oxides. And since the interaction of oxides with acids takes place with the participation of water as a catalyst - and sulfuric acid does not give up water - an effect called passivation occurs: a dense, insoluble and impermeable film of metal oxide protects it from further dissolution.
According to this mechanism, concentrated sulfuric acid is sent to distant places by iron and aluminum. It is noteworthy that if the acid is diluted, water appears, and it cannot be sent - the metals dissolve.
By the way, sulfur oxide SO3 dissolves in sulfuric acid and oleum is obtained - which is sometimes mistakenly written as H2S2O7, but this is not entirely true. Oleum has an even greater craving for water.
My own feelings from getting sulfuric acid on my hand: a little warm, then a little baked - I washed it off under the tap, it's okay. Do not believe in films, but I do not advise dripping on your face.
Organics often use chromic or "chromium mixture" - this is potassium bichromate dissolved in sulfuric acid. In fact, this is a solution of chromic acid, it is good for washing dishes from organic residues. When it hits the hand, it also burns, but in fact - sulfuric acid plus toxic hexavalent chromium. You will not wait for holes in your hand, except perhaps on clothes.
The author of these lines knows an idiot who used potassium permanganate instead of potassium bichromate. On contact with organic matter, it sighed a little. Those present managed to get off with a slight fright.
Hydrochloric acid
HCl
Above 38% in water does not happen. One of the most popular acids for dissolution - in this it is more abruptly than the others, because technologically it can be very pure, and in addition to acting as an acid, it also forms complex chlorides, which increase solubility. By the way, it is for this reason that insoluble silver chloride is very soluble in concentrated hydrochloric acid.
This one, when it comes into contact with the skin, burns a little harder, subjectively - it also itches, and it also stinks: if you work a lot with concentrated hydrochloric acid in a laboratory with a bad extract, your dentist will say “thank you” to you: you will make him rich on fillings. By the way, chewing gum helps. But not much. Better - extractor.
Since it is not oily and does not get very hot with water, causticity is only to metals, and even then not to all. By the way, steel in concentrated hydrochloric acid is passivated and says “no!” to it. What is used during transportation.
Nitric acid
HNO3
Also very popular, for some reason they are also afraid of her - but in vain. Concentrated - this is up to 70% - it is the most popular, higher - it is "smoking", most often no one needs it. There is also an anhydrous one - so that one also explodes.
Being an oxidizing agent, it passivates many metals that are covered with an insoluble film and say: “goodbye” - these are chromium, iron, aluminum, cobalt, nickel and others.
It instantly reacts with the skin according to the principle of a xantoprotein reaction - there will be a yellow spot, which means that you, %username%, are still made of protein! After some time, the yellow skin will peel off, as if burned. At the same time, it stings less than hydrochloric acid, although it stinks no worse - and this time it is more toxic: flying nitrogen oxides are not very good for the body.
In chemistry, the so-called "nitrating mixture" is used - the most popular consists of sulfuric and nitric acids. It is used in syntheses, in particular in obtaining a cheerful substance - pyroxylin. By causticity - the same hrompek plus beautiful yellow skin.
There is also "royal water" - this is a part of nitric acid to three parts of hydrochloric acid. It is used to dissolve some metals, mainly precious ones. The drip method for checking the samples of gold items is based on a different ratio and the addition of water - by the way, it is very difficult to fool specialists in this method with a fake. In terms of causticity for the skin - the same “nitrating mixture” plus stinks excellently, the smell cannot be confused with anything, it is also quite toxic.
There is also "reverse aqua regia" - when the ratio is reversed, but this is a rare specificity.
Phosphoric acid
H3PO4
In fact, I gave the formula of phosphoric acid - the most common. And there is also metaphosphoric, polyphosphoric, ultraphosphoric - in short, enough, but it doesn’t matter.
Concentrated phosphoric acid (85%) is such a syrup. It is an average acid in itself, it is often used in the food industry, by the way - when you get fillings, the tooth surface is first etched with phosphoric acid.
Her corrosivity is so-so, but there is an unpleasant nuance: this syrup is well absorbed. Therefore, if it drops on things, it will be absorbed, and then it will slowly corrode. And if there is a stain or a hole from nitric and hydrochloric acid, then from phosphoric acid the thing will fall apart, it is especially colorful on shoes, when the hole seems to crumble until it turns right through.
Well, in general, it is difficult to call it caustic.
Hydrofluoric acid
HF
Concentrated hydrofluoric acid is about 38%, although there are strange exceptions.
A weak acid that takes fluoride ions with a fierce love to form stable complexes with everything with whom it is possible. Therefore, it surprisingly dissolves what other, stronger friends cannot, and therefore it is very often used in various mixtures for dissolution. When it gets on the hand, the sensations will be greater from other components of such mixtures, but there is a nuance.
Hydrofluoric acid dissolves SiO2. That is sand. That is glass. That is quartz. Well, and so on. No, if you splash this acid on the window, it will not dissolve, but the cloudy spot will remain. To dissolve - you need to hold for a long time, and even better - heat it up. When dissolved, SiF4 is released, which is so beneficial to health that it is better to do it under a hood.
A small but nice nuance: you, %username%, have silicon in your nails. So, if hydrofluoric acid gets under your nails, you won't notice anything. But you won’t be able to sleep at night - it will hurt SO much that sometimes there is a desire to tear off your finger. Trust me friend, I know.
In general, hydrofluoric acid is toxic, carcinogenic, absorbed through the skin and a lot of everything - but we are talking about causticity today, right?
Remember, we agreed at the very beginning that there would be no fluorine? He will not be. But they will...
Inert gas fluorides
In fact, fluorine is a tough guy, you don’t really show off with it, and therefore some inert gases form fluorides with it. Such stable fluorides are known: KrF2, XeF2, XeF4, XeF6. All these are crystals, which in the air with different speeds and willingly decompose by moisture to hydrofluoric acid. Acidity is appropriate.
Hydroiodic acid
HI
The strongest (according to the degree of dissociation in water) binary acid. A strong reducing agent, which is used by organic chemists. It oxidizes in air and turns brown, which stains upon contact. Feelings on contact - like salt. All.
Perchloric acid
HClO4
One of the strongest (according to the degree of dissociation in water) acids in general (superacids compete with it - about them below) - the Hammett acidity function (a numerical expression of the ability of the medium to be a proton donor with respect to an arbitrary base, the less - the stronger the acid) is - 13. Anhydrous is a strong oxidizing agent, likes to explode, and is generally unstable. Concentrated (70% -72%) - an oxidizing agent is not worse, often used in the decomposition of biological objects. Decomposition is interesting and exciting in that it can explode in the process: care must be taken that there are no particles of coal, so that it does not boil too violently, etc. Perchloric acid is also quite dirty - it cannot be purified by subdistillation, the infection explodes! Therefore, it is rarely used.
On contact with the skin it burns, feels like salt. It stinks. When you see in films that someone threw a corpse into a container of perchloric acid - and it dissolved, then yes, this is possible - but for a long time or warm it up. If you heat it, it can explode (see above). So be critical of the cinematography (I think I saw it in 10 Cloverfield).
By the way, the causticity of chlorine oxide (VII) Cl2O7 and chlorine oxide (VI) Cl2O6 is the result of the fact that these oxides form perchloric acid with water.
And now let's imagine that we decided to combine the strong acidity - and the causticity of fluorine in one compound: let's take a molecule of perchloric or sulfuric acid - and replace all of its hydroxyl groups with fluorine! The rubbish will turn out to be rare: it will interact with water and similar compounds - and a strong acid and hydrofluoric acid will immediately be obtained at the reaction site. A?
Sulfur, bromine and iodine fluorides
Remember we agreed to consider only liquids? For this reason, it was not included in our article. chlorine trifluoride ClF3, which boils at +12 ° C, although all the horror stories that it is terribly toxic, ignites glass, a gas mask, and when pouring 900 kilograms - eats through 30 cm of concrete and a meter of gravel - all this is true. But we agreed - liquids.
However, there is a yellow liquid - iodine pentafluoride IF5, colorless liquid bromine trifluoride BrF3, light yellow bromine pentafluoride BrF5which are no worse. BrF5, for example, also dissolves glass, metals and concrete.
Similarly, among all sulfur fluorides, only disulfur decafluoride (sometimes also called sulfur pentafluoride) is a colorless liquid with the formula S2F10. But this compound at ordinary temperatures is quite stable, does not decompose with water - and therefore is not particularly caustic. True, it is 4 times more toxic than phosgene with a similar mechanism of action.
By the way, it is said that iodine pentafluoride was the "special gas" to fill the atmosphere in the escape shuttle in the last shots of the 1979 film Alien. Well, I honestly don't remember.
Superacids
The term "superacid" was coined by James Conant in 1927 to classify acids that are stronger than ordinary mineral acids. In some sources, perchloric acid is classified as a superacid, although this is not the case - it is an ordinary mineral.
A number of superacids are mineral, to which a halogen has been picked up: the halogen pulls electrons onto itself, all the atoms are very angry, and everything goes to hydrogen as usual: it falls off in the form of H + - bang: now the acid has become stronger.
Examples are fluorosulphuric and chlorosulfuric acids
Fluorosulfuric acid has a Hammett function of -15,1, by the way, thanks to fluorine, this acid gradually dissolves the test tube in which it is stored.
Then one of the smart ones thought: let's take a Lewis acid (a substance that can accept a pair of electrons from another substance) and mix it with Bronsted acid (a substance that can donate a proton)! Mixed antimony pentafluoride with hydrofluoric acid - got hexafluoroantimony acid HSbF6. In this system, hydrofluoric acid releases a proton (H+), and the conjugate base (F−) is isolated by a coordination bond with antimony pentafluoride. This forms a large octahedral anion (SbF6−), which is a very weak nucleophile and a very weak base. Having become "free", the proton causes the super-acidity of the system - the Hammett function -28!
And then others came and said, why did they take weak acid from Bernstead - and came up with this.
Tetrafluoromethanesulfonic acid
- in itself is already a superacid (Hammet function - 14,1). So, antimony pentafluoride was added to it again - they got a decrease to -16,8! The same focus with fluorosulfuric acid gave a reduction to -23.
And then a group of scientists from the Department of Chemistry at the American University of California, led by Professor Christopher Reed, hung out with colleagues from the Institute of Catalysis of the Siberian Branch of the Russian Academy of Sciences (Novosibirsk) and came up with carborane acid H (CHB11Cl11). Well, “carborane” was named for ordinary people, and if you want to feel like a scientist, say “2,3,4,5,6,7,8,9,10,11,12-undecachlor-1-carba-closo-dodecaborane (12)" three times and quickly.
This is what this beauty looks like
It is a dry powder that is soluble in water. This is the Strongest Acid at the moment. Carborane acid is about a million times stronger than concentrated sulfuric acid. It is not possible to measure the strength of an acid on conventional scales, since the acid protonates all known weak bases and all solvents in which it dissolves, including water, benzene, fullerene-60, sulfur dioxide.
Subsequently, Christopher Reed, in an interview with the Nature news service, said: "The idea of synthesizing carborane acid was born from fantasies" about molecules that have never been created before. Together with colleagues, he wants to use carborane acid to oxidize atoms of the inert gas xenon - simply because no one has done it before. What to say is original.
Well, since superacids are ordinary acids, they usually act, only a little stronger. It is clear that the skin will be burned, but this does not mean what to dissolve. Fluorosulfonic is a separate case, but everything is due to fluorine, as in hydrofluoric.
Trihaloacetic acids
Specifically, trifluoroacetic and trichloroacetic acid
Nice and pleasant combination of the properties of an organic polar solvent and a fairly strong acid. They stink - like vinegar.
The most lovable is trifluoroacetic acid: a 20% solution destroys metals, cork, rubber, bakelite, polyethylene. The skin burns and forms dry ulcers reaching the muscle layer.
Trichloroacetic in this regard is the younger brother, but also nothing. By the way, applause for the weaker sex: in pursuit of beauty, some go for the so-called TCA peeling procedure (TCA is TetraChloroAcetate) - when the upper coarsened layer of the skin is dissolved with this same tetrachloroacetic acid.
True, if the beautician talks on the phone, a fail is possible.
Well, something like this, if we talk about liquid and about causticity. Will there be more additions?
Source: habr.com