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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1answer
405 views

Best place to take off vacuum for distillation

I have seen vacuum take-off adapters that are essentially plugs, which could be placed at the top of a three-way above the fractionating column, and also straight and bent vacuum take-offs with an ...
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1answer
752 views

Does caffeine isolated from coffee contain harmane?

I'm not sure whether the caffeine contained in otc caffeine pills is made synthetically or isolated from coffee and other plants, but if the latter is the case, is it likely that it contains the ...
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2answers
12k views

Azeotropes and separation by distillation?

I have just recently learnt the theory of fractional and normal distillations and the basics of maximum and minimum boiling azeotropes. Most books say that the components of the mixture forming an ...
16
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1answer
41k views

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 ...
6
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2answers
247 views

Removing titanium from tantalum crucible

I'm trying to remove titanium filling from a tantalum crucible for a high-temperature effusion cell. I've managed to get a majority of the material out with tweezers, but some remains and is ...
9
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1answer
861 views

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 ...
2
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2answers
405 views

How are pure substances (elements, compounds, etc) produced? [closed]

How are large quantities of the substances we use in the lab generally produced? (As in the process from getting the stuff out of the ground to use in the lab) How 'pure' are they? Also: is it ...
2
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1answer
120 views

How are arsenic compounds removed from drinking water?

I used to live near a volcano where the groundwater contains naturally occurring arsenic compound. Since $\ce{As2O3}$, $\ce{As2S3}$, and $\ce{As4S4}$ are predominantly occurring in drinking water, ...
0
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2answers
269 views

Crystallization from a solution

I was wondering if there is any other way to crystallize materials from a solution other than using supersaturation? Thanks,
5
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1answer
213 views

Drying a distillate liquid

So I'm carrying out the distillation of some essential oil and I have to remove the water content in it. The usual method is using diethyl ether but I'm looking for a greener method. What can I do?
5
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2answers
2k views

How to extract elemental bismuth from pepto bismol?

I was trying to isolate elemental bismuth from pepto bismol (bismuth subsalicylate) using the process seen here but after I added hydrochloric acid, instead of getting a pink foamy substance, I got a ...
8
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1answer
891 views

What is the process for purifying KOH?

I'm partnered with a jewelry production company whose plating baths require $\ce{KOH}$. We're located in Indonesia, where import fees are absurdly high, and reliable suppliers are rare. A local shop ...
8
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1answer
26k views

Acetic acid freezing distilation

How can acetic acid be distilled by freezing when its freezing point is above the freezing point of water. Examples on the web show the water portion of the vinegar as ice and the acid as a liquid ...
15
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1answer
2k views

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 (...
12
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1answer
1k views

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, ...
12
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3answers
13k views

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 ...
11
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3answers
30k views

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 ...
7
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1answer
329 views

Negative retention for chloride in hydrolysate filtration

I tried to fractionate proteins as a function of their size with an ultrafiltration membrane. I observed a higher concentration of chloride in my permeate than in my feed or retentate. The proteins do ...
7
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1answer
1k views

What is the behavior of a Zwitterion during ion exchange chromatography?

We're interested in purifying a protein that has an azide moiety using ion exchange chromatography. Due to its unique structure, the moiety is a Zwitterion with a novel chemical behavior. My question ...
24
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3answers
684 views

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: ...
26
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1answer
7k views

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 ...

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