57
votes
Accepted
Why isn't the American nickel magnetic?
There are many types of magnetic properties, including ferromagnetism, paramagnetism, diamagnetism, antiferromagnetism, ferrimagnetism, superparamagnetism, metamagnetism, spin glasses, and ...
- 12.2k
38
votes
Why does mercury decolourise a gold ring?
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 ...
- 37.1k
34
votes
Is "stainless" a bulk or a surface property of stainless steel?
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 ...
- 14.2k
27
votes
Accepted
Will we ever run out of gold, silver, copper and other important conductors?
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 ...
- 5,462
25
votes
Why isn't the American nickel magnetic?
None of the US coins are magnetic (ferromagnetic), except for the 1943 Lincoln penny (Steel Cents, made in steel and zinc to save copper for ammunition during wartime), which are considered magnetic. ...
- 41.2k
21
votes
Accepted
Is "stainless" a bulk or a surface property of stainless steel?
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 (...
- 3,042
20
votes
How do manufacturer remove oxygen from metal during melting?
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 ...
- 31.4k
16
votes
How can steel be so different from iron, even if amount of carbon is small?
One of the key considerations is that much of the interesting mechanical behaviour doesn't occur within the bulk of the material - it occurs at the interfaces between crystals (known as grains). Grain ...
15
votes
How to separate Cu and Ni from alloy containing different metals such as Al, Cu, Ni, (Zn, Pb, Sn < 5%)?
First, the alloy $(0.5$ to $\pu{2 g})$ should be treated by $\pu{10 mL}$ nitric acid $32\,\%.$ All metals will get dissolved, except tin and silicon, which will be transformed into insoluble dioxide $\...
- 29.5k
13
votes
Accepted
What does it mean to 'fuse' ores and why do we use alkali metals in the process?
"To fuse" is another word for "to melt" (e.g. "heat of fusion"). Specifically, if you say you want to fuse two materials, you melt them in the hope that they will mix.
In this case, you melt the ...
- 12.2k
12
votes
Accepted
Why are the sulfide ores generally converted to an oxide and then reduced?
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.
...
- 31.4k
12
votes
Accepted
Does molten metal liquid chromatography exist?
An obstacle of implementation is that the blend of metals has to be kept liquid all the time the chromatography runs, top to bottom of the column, while the equipment around has to sustain the ...
- 30.6k
11
votes
Why does mercury decolourise a gold ring?
Once when I was doing an experiment I had the same experience; my ring was decolourised. I was afraid at first but we could reverse this process to achieve the gold colour once again.
There is no ...
- 465
11
votes
Accepted
Leaching of copper using zinc
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 ...
- 43.3k
11
votes
Is "stainless" a bulk or a surface property of stainless steel?
"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)...
- 3,777
11
votes
Why is the only natural source of radium compounds uranium minerals?
You can't find primordial radium because it's half life is too small compared to earths age.
Even the radium isotope with the longest half life, $\ce{^{226}Ra}$ has a half life of only 1600 years ...
- 3,151
11
votes
Why I am unable to see any electrical conductivity in Permalloy nano powders?
Nanoparticles are often pyrophoric, and may be coated to prevent spontaneous combustion. The particles' surface might be nitrided, or oxide coated, or coated with an organic chemical. Permalloy itself ...
- 34.8k
10
votes
Accepted
Obtaining 100% pure metal
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 ...
- 34.8k
10
votes
Which has more metallic character: aluminium or magnesium?
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:
...
- 9,089
10
votes
What does it mean to 'fuse' ores and why do we use alkali metals in the process?
As a comment of Karl's message, I would like to add that chromite $\ce{FeCr_2O_4}$ is the most important Chromium mineral. When mixed with $8$ times its weight of sodium carbonate, and heated to high ...
- 29.5k
9
votes
Accepted
What happens to the carbon in carbon steel when it rusts?
Cast iron has considerable free carbon as graphite, but carbon steel has iron carbide in cementite, $\ce{Fe3C}$ in a ferrite ($\ce{α-F}$e) matrix, along with other phases and additives. In a corrosive ...
- 34.8k
9
votes
Is "stainless" a bulk or a surface property of stainless steel?
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,...
- 91
9
votes
How can steel be so different from iron, even if amount of carbon is small?
Elastic deformation properties like stiffness (Young's Modulus) vary very little with alloying element concentration since we are only working on the pre-yield bond strength. A pure iron, a carbon ...
- 239
9
votes
Does molten metal liquid chromatography exist?
Molten liquid chromatography does not exist currently. However the problems you mentioned for purifying metals is very conveniently done using ion-exchange chromatography. A lot of difficult to ...
- 42.2k
8
votes
Reaction between alumina and aqueous sodium hydroxide, which one's right?
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) + ...
- 26.5k
8
votes
How do manufacturer remove oxygen from metal during melting?
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 ...
- 361
8
votes
Accepted
Does cold bluing steel prevent rust?
It provides limited corrosion protection. I would suggest just putting oil on it; more corrosion protection and it will not obscure the surface pattern which is most all that separates Damascus steel ...
- 3,777
8
votes
Accepted
Why do we use coke instead of coal in order to reduce FeO as basic reaction in ironmaking process?
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 ...
- 3,777
8
votes
Accepted
How can Ellingham diagrams be linked to Gibbs energies of formation?
The Ellingham diagram doesn't actually use molar Gibbs energies of formation $\Delta G_\mathrm{f}^\circ$ per se; it is more accurate to say that it uses molar Gibbs energies of reaction $\Delta G_\...
- 71.7k
8
votes
Accepted
Why are rare earth metals and platinum group metals are often found clustered together in ores
The factors that generate mineral concentrations are complex and often only partly known
Introduction: geology is complicated
The one thing we can be very certain about is is that the distribution of ...
- 37.1k
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