# Tag Info

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

The grey colour is an amalgam of mercury and gold. Mercury forms amalgams with many other metals. Some are used as chemical reagents in laboratory chemistry as they have different properties than the original metals involved. Gold amalgam is much greyer than gold. Silver amalgam has been used in dentistry. Mercury has been used in the extraction of gold in ...

27

How long will these reserves last? Short answer: longer than you think and will outlast me, you, our children and our grandchildren. Possibly last forever. Long answer: This is a fairly complex issue. There was a book published about this topic several years ago claiming that we are running out of metals. Turns out that the book had a major flaw in its ...

20

They use flux, that's how. That is, an inert substance which melts easier than the metal and floats on top, preventing it from oxidation in the air. Common fluxes for aluminum seem to be based on eutectic mixtures of various chlorides (say, $\ce{NaCl + KCl}$). Covering your crucible with a lid does not offer complete protection, and working in inert ...

18

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 ...

15

Above a $1000\ \mathrm K$, the $\Delta_\mathrm fG$ of $\ce {CO}$ from $\ce C$ is more negative than that of $\ce{CO2}$ formation from $\ce C$. Therefore, during smelting, when coke ($\ce C$) reacts with $\ce {SnO2}$, the formation of $\ce {CO}$ rather than $\ce {CO2}$ is thermodynamically preferable. Below that temperature, the reduction with carbon is not ...

13

AlMg3 is not the chemical formula of the alloy, it's the product name for a wrought alloy. Its technical sheet specifies the following composition: Product name AlMg3 Class of product Al-Mg alloy for MIG/TIG welding. Corresponding standards DIN 1732, SG-AlMg3, AWS A5.10, ER 5754 Nominal composition (weight %) Al: Bal. Si: 0.4 Mg: 3 ...

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

Why, it's simple: you heat a metal oxide with carbon, and you get the metal you were after, plus a byproduct of $\ce{CO}$ or $\ce{CO2}$ which easily flies away. Coal is still abundant on our planet. Try to pull that with a sulfide! I guess the reaction will not go in the first place, since $\ce{CS2}$ is a great deal less exothermic(*) than $\ce{CO2}$. In ...

10

We can. But I see few reasons why it is not used: Iron is much cheaper than zinc. There can be remaining residue of iron/zinc, coated by copper, or just being excessive. While copper can be melted away and iron stays, zinc would melt together with copper, causing unwanted impurity (unless wanted for making brass alloys) If we remove copper for ...

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

Two types of metallic character In fact, there are two type of metallic character if you look at the metal from the chemical point of view or if you look at the metal from the physical point of view: So it really depends on how do you define metallic character Chemical metallic character Since metallic character in chemistry is defined as: the ...

9

The only way to get a "100% pure" sample of an element is by mass spectroscopy, or something similar, which acts on each atom (or ion, actually) one at a time. So you could get a sample of pure rubidium of a few dozen atoms. Caveat: "100 % pure" applies only to those atoms actually observed... there could be other elements in the vicinity that have not been ...

9

Once when I was doing a experiment I have this experience, my ring was decolourised. I was afraid first but we can reverse it to the gold again. There is no reaction between gold and Hg and it is type of mixture such that NaCl is soluble in water. When the gold and Hg mixed they make a amalgam, and this thing is call as amalgamation.It also uses to allocate ...

8

My theory was to use electromagnetic separation, aka the Calutrons used in the Manhattan Project. Fine powder feedstock (check), into an arc discharge to vaporize and ionize (lots of good designs for high volume ion sources out there), electrostatic acceleration, then electromagnets to mass separate. Power with a solar panel array. No moving parts (except ...

8

According to A Conducting Crystal Based on A Single-Component Paramagnetic Molecule, [Cu(dmdt)2] (dmdt ) Dimethyltetrathiafulvalenedithiolate) J. Am. Chem. Soc., 2002, 124 (34), pp 10002–10003 : Single-component molecular metals should greatly extend the development of new types of molecular conductors. For example, while the first metallic molecule-...

8

Sigh - as pointed out by @user83678 some 3+ years after first writing this, I answered for Pd, not Pt. That will teach me to pay attention. But, the general answer remains the same. There are enough interactions of platinum with either lead, tin, or silver (a common component in lead-free solders) such that a platinum tip does not make metallurgical sense. ...

8

There are two aspects to this, firstly is actually reducing the pure metal from its oxides, usually called smelting, most metal ores are metal oxides so this is clearly an important part of primary metal production For example in iron production iron oxides are reduced by carbon, usually from coke which is also the fuel which provides the energy for the ...

8

The single most important factor is strength ( mechanical compressive ); coal is heated to make coke, the resulting coke is stronger than the original coal. Also, coke helps to make the charge of iron oxides and limestone more porous to permit gas flow up and droplets of liquid iron and slag down. The coke oven heating drives off volatiles from the coal, ...

7

An alloy is purely a mixture of metals (and sometimes non-metals) which are non-chemically bonded. So yes, you could mix steel and silver to create an alloy. There would be nothing stopping you from doing this, but I cannot say whether or not it would produce any desirable results. Mixing alloys with other materials is merely creating another alloy. ...

7

Much of this answer is based on a document available from NIST at Properties of Ternary Copper-Silver Systems [originally J. Phys. Chem. Ref. Data, 6(3) 621-673 (1977)] - this has an equivalent to the diagram in the question (which is just the surface of the liquidus). Now, since you are talking about balances of solid phases, it is also worth looking at the ...

7

Sort of, if you define metals as substances that exhibit some metallic behaviour Metallic elements are, well, the metals. But other substances can exhibit many of the properties of those metals. One well-known example if what you get when you dissolve a lot of sodium in liquid ammonia. Beyond a certain concentration, a new metallic-like phase if formed ...

7

Quoting from chemguide (emphasis mine): With hot concentrated sodium hydroxide solution, aluminium oxide reacts to give a solution of sodium tetrahydroxoaluminate. $$\ce{Al2O3(s) + 2NaOH(aq) + 3H2O(l) -> 2NaAl(OH)4}$$ Note: You may find all sorts of other formulae given for the product from this reaction. These range from $\ce{NaAlO2}$ (which ...

7

Both $\ce{Cu2S.Fe2S3}$ and $\ce{CuFeS2}$ are the equivalent means to denote chalcopyrite. The first notation, $\ce{Cu2S.Fe2S3}$, commonly used a few decades ago, shows that two sulfides are not just a mechanical mix, but form a chemical compound (same as for crystallohydrates, e.g. $\ce{CuSO4 * 5 H2O}$). The second one, $\ce{CuFeS2}$, is a formula unit, a ...

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

Reasons why Titanium is hard to extract and purify: The +4 oxidation state of $Ti$ is the most stable (due to its noble gas configuration) and so reducing $TiO_2$ to $Ti$ is quite difficult. $Ti$ has chemical properties which are similar to its neighbouring elements (Vanadium, Zirconium, Chromium) and the presence of compounds containing these elements in ...

6

I thought you asked a great question, one that I have wondered about myself. The answer, as best I could determine, is that the iron does oxidize. A good description of the Basic Oxygen Steelmaking process, today's descendent of the Bessamer process, says so anyway. The BOS process uses pure oxygen instead of the original Bessamer processes's air. It ...

6

There are no general conditions- indeed there no general conditions for the any of the forms of corrosion. Solubility is a factor and many other factors but it just comes down the actual interactions between a given liquid metal and another metal and the service conditions such as temperature, velocity, impurities. Liquid-metal attack has the following ...

6

One of the reasons why non reactive metals are good conductors is that they are good at staying as metals. Most metals react with the atmosphere to form oxides. And the majority of oxides are insulators or semiconductors. Of course there are few exceptions to this rule. Also, just a note: calcium and iron have better conductivities than platinum.

6

When we start talking about Fineness of metals we can deal with some misunderstanding. We generally have to make a distinction between absolute purity and the common metals basis purity. The first refers to all the impurities (all the elements of the periodic table) the second refers only to metals. On industrial level is not possible to reach 100% absolute ...

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