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Questions tagged [purification]

For questions about purification - the process of rendering something pure, clean of foreign or undesired elements. Not to be confused with [metallurgy] or [chromatography].

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Are there any general rules for choosing solvents for recrystallization?

Re-crystallization is a nice way of purifying a product, but choosing a suitable solvent, if you can't rely on the literature, seems like a lot of trial-and-error. Are there any general rules on which kind of solvents could be used for…
Mad Scientist
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What is the origin of the bactericidal properties of silver in water?

I often hear that water gets purified by being in a silver vessel, which sounds plausible because of bactericidal feature of silver. What doesn't sound plausible, though, is the way it's explained: that silver releases ions into the water. Since…
Evgeni
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What makes oceanic desalination so expensive?

What specifically makes oceanic desalination so expensive?
Lora Wesley
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Un-denaturing industrial alcohol

I have a question regarding the denaturation of industrial ethanol with methanol to discourage its consumption. The boiling point of methanol is 64.7 °C, while the boiling point of ethanol is 78.37 °C. Wouldn't it be trivial then, to separate the…
René
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How does alum improve the settling of particles to produce 'clean' water?

How does the addition of alum — potassium aluminium sulfate or $\ce{KAl(SO4)2}$ — help settle the dust particles in water? There was such a statement in my Year 9 textbook, and so I was wondering how exactly alum does it. Edit: I have posted an…
Yatharth Agarwal
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What happens during cleaning silverware?

I know two distinct recipes for cleaning silver: Put them into a pot with some club soda and a piece of aluminium foil and pour over a hot water. Gently clean silverware with a fine chalk powder (obtained from a pharmacy). I'd be happy to…
Petr
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Copper Chloride: neutralizing and disposal

I plan on etching some PCBs with hydrochloric acid and hydrogen peroxide, which will therefore produce some kind of copper chloride (green color) which is highly toxic if released into the environnement (it may be useful as an herbicide, but I don't…
user51166
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Old sample of sodium tetraphenylborate—why it is red?

I have a really old sample of sodium tetraphenylborate. It should be white, but it is red. Does anyone know what was formed and how it influences precipitation of cations in water?
BalticMusicFan
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What does it mean for meth or any other compound to be 'pure'?

In Breaking Bad, Walter White can cook $99.1\%$ pure meth. In general what does it mean for a substance to be pure? In this case, what exactly does it mean for meth to be pure? Does higher purity mean less unhealthy? More addictive? Giving more…
BCLC
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Difference between lab-grade and food-grade purity?

What is the difference in purity betwen lab-grade and food-grade when talking about potentially consumable compounds? As an example let's take ascorbic acid powder: if it's marked as lab-grade, does that mean it is also fit for consumption? In…
Casper
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How do chemists measure purity in high purity metals and other reagents?

I have noticed that gold bars are often marked "999.9" fine: Whenever I have metallurgical assays done, they always seem to do them with ISP or DSP or whatever, some spectrometer-based system. These systems have errors of 1% to 2%. When I complain…
Shaka Boom
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Isolating salt from sea water using filters

Could a filter be used to isolate salt from sea water? Could we say that the water molecules are smaller than the molecules of salt dissolved in the water. I have no relation to chemistry or physics, so pardon the question if it's too naive.
NoChance
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Is it safe to condense water into a liquid nitrogen trap?

I'm trying to remove water from an imidazolium salt (i.e. dry the salt). However I want to know if it is safe to remove the water under vacuum. Is it safe to condense water into a liquid nitrogen trap? Wouldn't the water freeze in the trap since…
Amadi
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Purification/Extraction of Sodium Permanganate

I read this question and answer, and it seemed like a rather nice way to make sodium permanganate. Using the method with sodium hydroxide, I produced a solution. Once filtered and decanted, it was dark green. At first this seemed somewhat strange,…
ChemBird
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What acid can dissolve thorium dioxide?

In one of my projects (which is about alpha-voltaic cells, don't worry, I know that thorium isn't a strong alpha source, it's only for measurements) I would need to get water soluble thorium compound from a small sample of thorium dioxide for…
L.Gyula
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