# Tag Info

37

Other than a nuclear reactor, the only other chance is to dump it into a volcano. Having a much higher density than magma, it will just fall through until it hits earth's mantle. Then it's really gone. OK, dissolved and diluted in the Atlantic is also quite safe. P.S. Warning: If the bullion gets stuck in the volcano, which later explodes Krakatau-style, ...

30

As other answers have pointed out, you can't 'destroy' gold chemically. Putting it in a nuclear reactor for an extended period of time will functionally convert most of it to an isotope of mercury. If you really want to get rid of it, and you have lots of funding, you could launch it on a rocket into the sun (or another star, or better yet a black hole). ...

30

Let's divide the steel world into two classes: 1) rusting steel and 2) stainless steel. Rusting steel, in the presence of oxygen and moisture, will oxidize, forming hydrated iron oxides/hydroxides which have a greater volume than the original iron, and which have relatively little adhesion to the metal. They curl up and continue to expose bare metal, and so ...

29

Not destroying gold, but still giving a good appearance, is this time-honored story of how two golden Nobel prizes were "hidden" from the Nazis by dissolving the gold into aqua regia. The aqua regia, of couse, had only a limited shelf life; but the soluble gold species it produced could be retained indefinitely. After the war the gold was reduced, ...

19

It is usually a bulk property though you would need to know exact regulations for your country to be certain. Stainless steel is steel (i.e. iron + a little bit of carbon) alloyed with another metal which makes it resistant to oxidation by atmospheric oxygen (usually chromium). It does not mean though that it would resist to strong acids (e.g. concentrated ...

14

Step one: trap $\ce{CO2}$. This can be done using specially selected amines, like triethanolamine. Aminosilicones (a common chemical used in hair conditioner), can also do this. Step two: release trapped $\ce{CO2}$. In case of triethanolamine you'll have to boil mixture. Step three: mix $\ce{CO2}$ with hydrogen (hydrogen is produced by electrolysis of ...

13

There are lots, and I mean lots of methods and software programs to produce partial charges. See Wikipedia for a small (incomplete list) Let's start with the basics. The idea of a partial atomic charge, while useful for concept, can not be defined uniquely. Quantum chemical methods (whether wavefunction or DFT) produce some sort of electron density. ...

12

This is a nice question. Although I do not speak with authority on diamonds, most crystal surfaces have several imperfections which mitigate the hanging valencies that would otherwise appear for the atoms (constituents in general) at the surface. Impurities. This is the primary method which helps satisfy the unfulfilled valencies at the surface. Many ...

12

There are two common arguments presented as for why $\Delta H < 0$: Argument (1): Well, indeed I see nothing wrong with the argument presented by the textbook. If adsorption takes place spontaneously, then one can conclude that the change in Gibbs free energy of the process is indeed negative. Since, the entropy change associated with process is ...

11

The second law of thermodynamics states that the entropy of the universe always increases. $$\mathrm{d}S > 0$$ In the case of adsorption the entropy of the system; the gas being adsorbed; decreases but the entropy of the surroundings;the rest of the gas and the surface (and everything else in the universe); increases and this outweighs the decrease in ...

11

If you don't use any nuclear technology, you can't destroy gold. Everything that you can do to the gold, can be undone.1 What you can do: you can make its reconstruction economically infeasible. However, gold is Valuable Very stable (chemically) and non-reactive. Because of these, gold can be easily extracted from practically any gold compound. What ...

10

Coagulation is a process which involves coming together of colloidal particles so as to change into large sized particles which ultimately settle as a precipitate or float on the surface. Coagulation is generally brought about by the addition of electrolytes. When an electrolyte is added to a colloidal solution, the particles of the sol take up the ions ...

10

TL;DR Note that the passive layer forms on the surface, there needn't be any change to lattice constant. Chromium needn't migrate , the Cr present on the surface will form the layer to protect it. The key point is how the layer develops from say a single-atom layer of oxide to the usual/maximum width by migration of electron and oxygen in the oxide ...

10

In my fab experience, the answer is no, you are not going to inhibit deposition of silicon with some other material. You might well change the final grain size, but it will deposit. Furthermore, LPCVD generally has good sidewall coverage, so you can't use a lift-off mask either. The OP asked for references, so lets dig in to those. First, it is somewhat ...

10

"Stainless" is not a specific definition. The stainless steel with the least alloy is $5\% \; \ce{Cr}$ ( grade 501) according to AISI (It can't be cut with an oxygen/acetylene torch-like regular steel). API considers $\ce{Cr :Mo}$ (9:1) as stainless for oil well tubulars. SAE consider $12\% \; \ce{Cr}$ as stainless (most modern auto exhaust pipe). Stainless ...

9

Activated charcoal is a great adsorbent because of it's huge surface area. While it doesn't bind very many ions/atoms/molecules per surface area (which is the characteristic of a 'good' adsorbent), due to very big surface area per unit of mass it can adsorb a lot of particles. Actually, process of 'activating' charcoal is designed to maximize the surface ...

9

You did the right thing by neutralizing with a base. The best solution is to let time heal the stain. The surface is obviously damaged, but there is no way to reverse that damage. The stain will only go away if someone keeps on scrubbing the area until a new surface is exposed. The good news is that dirt, soil, and water will slowly remove and even scrub ...

8

At the surface of a diamond, the carbon atoms are generally bound to various other atoms (or groups of atoms) with lower valence. In principle, pretty much anything that could act as a substituent group in organic chemistry could also be bonded to the surface of diamond, but in practice, you're most likely to see simple groups with low reactivity, mostly ...

7

The curling up has a simple reason: the burning was not uniform. Paper contains water (really!), and heating it makes it lose the water. Now, paper is a bad conductor of heat. When you burn it, inevitably the flame will be mainly on one side(the side that's pointing up). The flame will transfer heat to nearby regions of paper, and evaporate some (or ...

7

Quick and simple: Steel = iron + carbon (less than 2%; also called "forgeable iron") Adding chromium (min. 12 %) makes it stainless. These chromium atoms are spread over the full volume of your block, also on the surface of it. There they create a thin layer of oxygen atoms. This layer makes the steel stainless. So when you cut your block in half, a new ...

6

Charcoal isn't a particularly good adsorbent even though it is chemically very similar to activated carbon. Activated carbon is usually made by more specialised processes that guarantee the final product will have a very large surface area (often >1,000m2/g). Manufacture usually involves pyrolysation with hot gasses, but many forms are also further ...

6

I see three reasons: Activated carbon is commonly used to adsorb organics, that should bind well on coal. For many purposes, activated carbon is treated with potassium or iodine to provide ions for charged centers. Charring organic stuff is a cheap and easy way to create large surfaces for adsorption.

6

Here's two links (1, 2) that show the simple scheme on forming monolayers. The essential figure is also shown here. For the second part of your question... I can only point out this article that describes which properties change, if you make the molecules more bulky or add chloride, etc. I would guess that APTES has well known properties and they are "...

6

There's actually two questions being asked here: What is holding ink on paper? and Why do some inks take longer to dry? Ink sticks to paper because it has a high affinity for the medium it's being applied to. To group things into simple categories we could say, there are hydrophobic inks (non-polar inks that don't like water) and hydrophilic inks (...

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

As acknowledged in your question, there are a large number of factors at play here. The most basic of these is that there are three fundamental mechanisms by which freezing of a droplet can initiate when in contact with a superhydrophobic surface: 1) heterogeneous nucleation where an ice freezing nucleus (IFN) is present in the water droplet, 2) ...

6

Gold is extremely difficult to get rid of, either chemically or physically. Gold is produced when a massive star goes supernova. Every single atom of gold in the entire universe is the result of the death of a star. So, a lot of energy went into the actual creation of the gold to begin with. More energy will be needed to destroy it's very atomic structure. ...

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

In order to explain the Schuze-Hardy rule, you have to take into account that you are working with a colloidal dispersions stabilized electrostatically. The stability of this dispersions is well described by the DLVO theory. According to this theory, the particles interaction potential can be expressed as the sum of two contributions, $$V_T = V_A + V_R$$ ...

5

It's always good to clean glass surfaces with oxygen plasma or UV ozone treatment before silianizing, but 108° is pretty good with an alkylsilane. The best you will be able to do with this type of surface treatment is using fluorosilanes. Silanization agents are basically made of three parts, a functional group, a linker and a coupling group: The coupling ...

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