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41

The potassium is not added first because the potassium does not intrinsically make stronger glass, it is the substitution of a larger ion for a smaller one that does. To understand why ion exchange strengthens glass, you have to understand why the ion exchange makes the glass harder. The process of ion exchange hardening is done at a temperature that allows ...


26

Is it crystallization? You are correct. The main difference is that sand is crystalline and glass is not—it is amorphous. The main component (> 95%) of common yellow sand is quartz (the mineral whose composition is SiO2). Note that not all sand is quartz. There are white sands containing calcite (CaCO3) and black sand (containing various heavy minerals). ...


25

Chemically-strengthened glass is similar tempered glass in that the outside of the glass is under compression, while the inside is not compressed. If all the sodium in chemically-strengthened glass were to be replaced by potassium, there would be no difference in stress between the interior and the exterior layer. How does this difference between layers ...


18

Are there other ways of "chemical strengthening" besides cationic exchange that can be utilized to strengthen the glass, keeping it flexible and less fragile at the same time? In a word: No. To understand why ion exchange strengthens glass, you have to understand why the ion exchange makes the glass harder. The process ion exchange hardening, its done at ...


13

Obsidian This is a volcanic glass, formed when rhyolitic lavas cool too quickly for crystals to form. From a chemistry point of view, it's a mixture of silicon dioxide, aluminium oxide, with sodium ,potassium, calcium and iron oxides in various quantities. These lavas will also contain significant volatiles (water and $\ce{CO2}$) held in solution by ...


11

Rather than working on your technique, check whether other test tubes are available. Apparently, a glass-like material with a very low thermal expansion coefficent would be a good choice. The glassblowing shop at the University of Delaware provides a nice overview of the possible materials and their properties, and there are definitely additional online ...


11

$\ce{XeF_6}$ can't be stored in glass as it reacts with the silica that makes up the glass $\ce{2XeF_6 + SiO_2 -> 2XeOF_4 + SiF_4}$ This can proceed further to eventfully make $\ce{XeO_3}$: $\ce{2XeOF_4 + SiO_2 -> 2XeO_2F_2 + SiF_4}$ $\ce{2XeO_2F_2 + SiO_2 -> 2XeO_3 + SiF_4}$ Dry $\ce{XeO_3}$ is highly explosive ... That is why both $\ce{...


9

You could proceed from either end member of the olivine solid series and yield $\ce{SiO2}$ as you suggest. However, I'd consider mechanisms that have been researched in the course of studying so-called mineral sequestration in addition to what you've written, especially considering the energy requirements you propose: the mineral sequestration reactions are ...


8

Some rust and stain removers (like Whink) contain hydrofluoric acid* at low concentrations (1-2.3%) Here is the MSDS for Whink: https://www.whink.com/cmssites/ws0811www.whink.com/uploads/Documents/Rust%20Stain%20Remover%20SDS.pdf Now, at those concentrations it would probably take a while to dissolve silica, but it would be arguably quicker than a $\ce{NaOH}...


8

This is not a chemical process. Objects typically expand when heated. Think in railway profiles in the summer, think in loosening a stuck nut by heating it with a blowtorch. However, when the material is under stress and a bad heat conductor, unevenly heating will result in cracking. While it is a pity for the cup, the breaking of glassware to thousands ...


7

Yes, it’s coincidental. There is no expectation that prime (or near-prime) atomic weight means anything for the element itself. In fact, your affirmation is not even true: on the list given by Wikipedia, the first two examples are: $\ce{Au_75 Si_25}$, your assertion is true “an alloy of 77.5% palladium, 6% copper, and 16.5% silicon”, and your assertion isn’...


7

As Ivan explained, a glass is by definition amorphous. However, you can take a quartz crystal (silicon dioxide, which is the main ingredient of glass) if it is of high purity and optical quality, and machine it into a transparent object such as a window pane.


7

$\ce{HF}$ reacts with glass ($\ce{SiO2}$).[1] $$\ce{SiO2 + 4HF -> SiF4 + 2H2O}$$ $\ce{SiF4}$ is not a solid that consists of vertex-connected tetrahedra like $\ce{SiO2}$ but is a gas at room temperature. Technically, $\ce{HF}$ is not a solvent since in this case it reacts with the glass vessel. According to Spierings:[2] $\ce{HF2-}$ ions are ...


7

To really answer this, you need to characterize the glass in terms of its properties, and not something like its ability to resist being scratched. Scratch resistance is a behaviour, and not a property. There are many ways of making something more scratch resistant. "Hardness" itself is a behaviour, and not a property. In any case, it might be that they'...


7

Let's start out by covering the Why? Glasses used in automobiles are designed to break in tiny pieces. Imagine you're driving down a dark highway hitting dangerously high speeds and then suddenly you lose control and crash. If the glass used was not to shatter in tiny pieces rest assured you would not remain in one piece. Essentially it shatters for ...


7

Gold plating glass could probably be 99.99% complete. It would make a nice mirror and would probably stay unoxidized for a long time. However, if I wanted to remove the gold, I think I would rinse the glass with HF solution, or perhaps NaOH solution, either of which would find those teeny tiny gaps and undercut the whole gold plate. I don't think there ...


6

I'm not sure where you get the idea that glass is linear. What makes a glass is the lack of long range ordering, though in fused silica, the approximate tetrahedral structure of $\ce{SiO4}$ is maintained (this is a 2D section, the fourth oxygens are not shown): Source In normal glasses, there is no significant net dipole moment across the entire structure,...


6

The most common glass-etching powders are solid ammonium bifluoride and solid potassium bifluoride. See for example the Material Safety Data Sheet for “EtchON Acid-Frost Glass Frosting Powder”, or this one. This is not a definite identification, but it fits your description, and those two are the most commonly available such chemicals. Disposal is a bit ...


6

Borosilicate glasses are a family that has many members with differing properties. You can look up the provider for your glass, and check whether it is transparent in the near infrared. I think it would be in most cases (see here for one example).


6

As A.K. notes, it is the substitution of larger atoms for smaller atoms that adds stress to the glass, making it stronger. So you can't increase the stress by starting with a larger metal, but you could on the other hand start with a smaller metal: Chemically strengthened lithium aluminosilicate glass (Int. Patent Application)


5

Professional glass blowers use graphite paddles to "push" the glass around. But to bend a heated glass tube you need to know that glass is a very poor conductor of heat. Thus it is possible to grasp the heated tube six or so inches from the heated spot and just bend the glass. This works well for small bore tubing. Just be careful putting the bent tube ...


5

Regular test tube is not really a good choice for rapid cooling for two reasons: it is often cheap glass, it has a relatively thin wall, and large space for the sample inside. This later is important, because if you want to cool down something really quick, it should be relatively small, and have good contact with the wall. I assume you want to cool ...


5

The previous answer is not really helpful because you would need huge amounts of CO2 which are not available on the moon. You need 2 moles of CO2 to generate 1 moles of SiO2. You simply do not have that amounts of CO2. Furthermore, assuming you do someone get that CO2, you need to physically separate the Mg and Fe carbonates from the silica. One way would ...


5

It is very difficult to make a container that does not introduce impurities to a liquid you place into it. As mentioned in the comments to the question, storing in a glass bottle will result in ions in your formerly pure water. This is thought to proceed by a mechanism called ion exchange (source): $$\ce{ Glass.Na+ + H3O+ -> Glass.H3O+ + Na+}$$ The ...


4

In theory, yes it is possible. In practice, not really. First of all, the anorthite on the moon is never pure anorthite ($\ce{CaAl2Si2O8}$) but rather an anorthite-albite ($\ce{NaAlSi3O8}$) solid solution. That is, the single crystal contains both components. The diagram you added there, where it says "mole %"? The other stuff is albite. Now, back to glass ...


4

In $\ce{SiO2}$ etching, there are two active fluorine-containing species, $\ce{HF}$ and $\ce{HF2-}$. The rate of etching at 25 degrees C in Angstroms per second is: $$9.66[\ce{HF2-}] + 2.50 [\ce{HF}] -0.14$$ according to A Study of the Dissolution of SiO2 in Acidic Fluoride Solutions J. Electrochem. Soc. vol. 118, pp. 1772-1775. The relavent equilibrium ...


4

While a glass is generally considered to be a supercooled, configurationally frozen liquid, not all amorphous solids are glasses. For example, amorphous silicon is a four-fold coordinated semiconducting solid, much like crystal silicon. Liquid silicon is 8-12 fold coordinated with metallic bonding. Amorphous silicon has been shown to display a first-order ...


4

Yes, it is correct that the surface of glass has silanol ($\ce{Si-O-H}$) at the surface. This is because water will react at the surface to relieve bond strain of a $\ce{Si-O-Si}$ bond to form $\ce{Si-O-H H-O-Si}$ pairs. additionally there is sodium siloxide at the surface ($\ce{Si-O-Na}$) which will release sodium hydroxide on contact with water $(\ce{Si-O-...


4

Well, XPS analysis should detect atoms as light as Carbon, but not atoms as light as Hydrogen. Far be it from me to claim any expertise on microscope sliders, but I have used one or two in my career, and I am hazarding a guess. It is likely a pure glass ($\ce{SiO2}$) sheet laminated with some acrylic glass. The hydrogen in the acrylic polymer are too light ...


3

You are correct: it's not both. Why? What you've heard is nonsense. Very old window panes are thicker towards one side because of how they were made at the time. It became common practise to put the thicker edge at the bottom, because it was less likely to exceed the acceptable stress on the thinner area. Contemporary windows have been found with the ...


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