How To Dissolve Glass With Acid?

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Do not repeat the experiments shown in this video!

So, today I want to tell you about such a substance as hydrofluoric acid, which is one of a few acids that can dissolve glass.
This acid, unlike other corrosive substances, is stored in polyethylene bottles, as it does not corrode them (and obviously cannot be stored in glass bottles because spoiler alert it dissolves glass).
This acid is obtained from fluorspar by the use of concentrated sulfuric acid on it.
Looking at this substance from the outside, it’s a transparent liquid with a pungent smell, slightly fuming in air due to the forming aerosol from the water in air.
You need to be extremely cautious when working with such substance, since when exposed to the skin, hydrofluoric acid behaves extremely treacherously.
Burns caused by the hydrofluoric acid heal very poorly.
By the way, the method of dissolving corpses with this acid that is shown in the Breaking Bad series would have hardly worked, since though hydrofluoric acid dissolves the bones well it doesn’t dissolve well the living tissues.
To demonstrate the dissolving glass property of hydrofluoric acid, I decided to grab a piece of glass that is used for microscopes and covered it with a layer of tape, after which I cut out the name of our channel, therefore revealing the glass in that area.
Now I’m moving the piece of the glass into a plastic cup with the solution of acid.
Remember that It is only possible to work with hydrofluoric acid in plastic vessels.
Also, I decided to pour some of the hydrofluoric acid into a regular silicate glass jar to see how much glass it would eat in one hour.
Let's see now, how much this acid corrodes metals, and let’s start with zinc.
As an example, in hydrochloric acid, zinc reacts very actively, but here in the concentrated hydrofluoric acid zinc dissolves rather sluggishly.
All because of the huge difference in the electronegativity of the fluorine and hydrogen atoms that make up this acid, and also because of the small size of the fluorine atom.
In the solution, the fluorine atom does not release the hydrogen atom from itself, which prevents the formation of free protons in the solution.
It is the ability to form free protons in a solution that can tell us the strength of an acid.
However, if instead of zinc we will use titanium, which practically is not really dissolved in other acids, however it will dissolve much more actively in this acid.
All due to the fact that fluoride ions from the acid contribute to the formation of complexes that are highly soluble with titanium.
Let's take another low-active metal - hafnium, which in chemical activity is similar to glass due to the strong oxide film covering this metal.
As we can see, it dissolves in the hydrofluoric acid even better than titanium, again due to the fact that being in this acid the oxide film immediately dissolves from the surface of hafnium, and so the unprotected metal begins to actively dissolve.
These reactions reminded me very much of the reaction of aluminum and sodium hydroxide, in which, also because of the dissolution of the oxide film from the aluminum surface, the latter begins to actively dissolve in water.
Additionally, if you mix the hydrofluoric acid with nitric acid, you will get a mixture that can dissolve the most stable metals, such as, for example, tantalum, or platinum.
Now, let's go back to our dissolving glass jar.
After an hour of etching the glass with hydrofluoric acid, we can now check the damage done to the glass.
The glass jar got covered with a white coating consisting of sodium and calcium fluorosilicates, this coating is easily removed, after which you can feel the etched glass is now rough.
This reaction is sometimes used by artists to apply beautiful matte patterns on the glass.
By the way, speaking of patterns, now it's time to check our inscription on the glass.
You can see that the letters are made of the same coating as the coating in our jar, I also managed to remove it quite easily.
Using macro photography, we can see the thickness of the glass layer that got dissolved by the hydrofluoric acid in just one hour, which is somewhat impressive. The inscription looks very distinct, with beautiful blurriness on the affected area which reminds me of crystals.
Nowadays, hydrofluoric acid is being used for creating catalysts in oil refining, in the production of Teflon, and also for the creation of cryolite, which is an indispensable additive in the production of aluminum from ore.
To conclude, hydrofluoric acid is a rather dangerous and an unusual substance, though, despite all the danger, is an indispensable substance in modern chemical industry.