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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26
votes
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 ...
24
votes
3answers
682 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: ...
20
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3answers
14k views

What makes oceanic desalination so expensive?

What specifically makes oceanic desalination so expensive?
18
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6answers
9k views

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 °...
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 ...
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 (...
14
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1answer
455 views

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?
13
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3answers
11k views

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 ...
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 ...
11
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1answer
292 views

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 ...
9
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1answer
858 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 ...
9
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1answer
849 views

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 ...
8
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2answers
1k views

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 ...
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 ...
8
votes
1answer
890 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 ...
7
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2answers
4k views

Removal of tetrabutylammonium from an organic reaction

I need to synthesize some organic compound for my Ph.D. research. Everything went OK during the synthetic route but got messed up at the very end. In my final step (once the final compound has been ...
7
votes
1answer
562 views

How does activated carbon trap impurities?

I've tried and I've tried to find an answer to this all over the web, but I can't seem to find an in depth explanation. To the best of my knowledge, activated carbon has a very microporous structure ...
7
votes
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 ...
7
votes
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 ...
6
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2answers
734 views

Remove salt from dirt

I have a mixture that contains out of dirt/sand and salt. I want to extract and measure the salt. What would be the best way to extract the salt from this mixture?
6
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2answers
2k views

Recrystallisation of dibenzylideneacetone

Recently, I carried out the synthesis of dibenzylideneacetone. I had a lot of problems with the purification process, especially the part involving recrystallisation. I was instructed to carry out the ...
6
votes
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 ...
6
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1answer
1k views

Why are 'table salt and sugar are both terrible candidates for recrystallization'?

I received a comment on one of my other chemistry questions stating that table salt and sugar are both terrible candidates for recrystallization, albeit for different reasons. Why are salt and ...
6
votes
1answer
2k views

How to make artificial sea water

My 7th grader is embarking on a long-term science project and I'm on tap to "help." He is showing a strong interest into finding ways to get drinking water to the masses. His idea is that we need to ...
6
votes
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 ...
5
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3answers
1k views

How to extract pure potassium carbonate from ash?

In our village, lots of ash is produced which is thrown off. I want to extract pure potassium carbonate from that ash. I am able to extract the potassium compound and a soluble compound by ...
5
votes
1answer
774 views

Purification of Ethanol

In Vogel's organic book, they have mentioned that in the Lund and Bjerrum method of purification of ethanol, magnesium is added, which forms ethanolate. But they said to activate the magnesium first ...
5
votes
1answer
913 views

HCl/diethyl ether + Nitrogen?

Just wondering if anyone can tell me why bubbling nitrogen through a solution of $\ce{HCl}$/diethyl ether catalyst would remove said mix from my solution. My current thought is that the $\ce{N2}$ ...
5
votes
1answer
28k views

Why is crystalline aspirin washed with chilled water in the purification process?

Take as example this or even better this: Wash the crystals with 2-3 ml of chilled water. Why does the aspirin need to be cooled down? And why do we wash the aspirin with chilled water?
5
votes
4answers
287 views

To heat or not to heat; distillation?

One of the questions in a recent past paper I completed was: One way to make water from the reservoir suitable for drinking is by distillation. Describe how water is distilled. And I answered ...
5
votes
1answer
89 views

Protein purification with Cobalt

Cobalt exhibits a more specific interaction with histidine tags, resulting in less nonspecific interaction than nickel. For this reason, cobalt is the preferred divalent cation for purifying His-...
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 ...
5
votes
1answer
273 views

How to make a sephadex slurry

I want to purify crude alpha-amylase with column chromatography. I am using a spehadex 75, but for some reason I can't find any information on how to make the slurry. I can quickly find a lot of ...
5
votes
2answers
1k views

Calculating the theoretical percent purity of a recrystallization

The sample contains some percent A and some percent B with A being the majority. The solubility for both is given at two different temperatures. One where both are very soluble and one where both are ...
5
votes
1answer
212 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?
4
votes
1answer
2k views

Mechanism of protein precipitation with TCA

In practice, TCA (trichloroacetic acid) is widely used for quantitative protein precipitation, but so far I have failed to discover the exact mechanism of TCA action. I highly doubt it's just the ...
4
votes
2answers
633 views

Shea Stearin Extraction by Dry Fractionation

I have been able fractionate palm oil and extract palm stearin using the following method: Melt the palm oil (over 80 °C) Keep the melted oil at 33.5 °C for 24 hours (using an immersion circulated ...
4
votes
2answers
54 views

Should I do solvent extraction for Buchwald–Hartwig amination?

I am conducting a synthesis involving Buchwald–Hartwig amination. Catalyst is $\ce{Pd2(dba)3},$ ligand is $\ce{P(o-tol)3},$ base is $\ce{Et3N},$ and solvent is toluene. Image below is the proposed ...
4
votes
1answer
777 views

Removal of octadecanoic acid from paraffin wax

I have some very plain candles. I don't think they contain anything but paraffin wax and octadecanoic (stearic) acid, since they are odorless and very hard to bend, tending to crack instead (even at ...
4
votes
1answer
151 views

Purification of primary amines using Schiff base immobilization

I want to purify all primary amines containing compounds in a complex mixture (cell-extracted metabolites). I'm unaware of any published methods to do so. So I am thinking of making my own using a ...
4
votes
1answer
126 views

How to remove nitrose gasses from ozone gas mixture?

I produce ozone gas with an ozone generator based on corona discharge principle. These kind of ozone generators have the disadvantage that if $\ce{N2}$ is present, a bit of $\ce{NO}$ and $\ce{NO2}$ ...
4
votes
3answers
7k views

What are disadvantages of using sublimation vs. recrystallization as a method of purification?

I can only think that a small sample can be sublimed while a bigger sample size can be recrystallized. Are there more?
4
votes
0answers
171 views

How can should one separate and purify benzophenone from salicylic acid?

I am working with two solids and I know that they are benzophenone (s)(ketone) and salicylic acid (s) (carboxylic acid). I am curious to know what is/are the best method of extraction and ...
4
votes
0answers
297 views

Refining Tin (Sn)

I am a Copper Cookware Tinner & have a problem in reusing much of the tin that I end up sweeping off the floor etc. Prob about 5kg over the year & it would be great to save this? Now, my ...
4
votes
0answers
5k views

Role of hydrochloric acid and sodium hydroxide in isolation of citric acid from lemon juice

I'm trying to extract citric acid from squeezed lemons. After studying the subject, I found a lab manual [1, p. 68]: ISOLATION OF CITRIC ACID Reagents: Lemon juice (ca. $\pu{100 mL}$ – 3 lemons) $\...
3
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3answers
998 views

Is there a method to separate iron from mercury?

The mercury is contaminated with iron. Is there any way to remove iron from mercury?
3
votes
3answers
889 views

Obtain precipitated iron?

Is it possible to obtain pure, precipitated iron with no oxidation by some chemical process? Alternatively is it possible to electrically purify iron using an anode and cathode?
3
votes
1answer
393 views

Textbook chemistry vs Real life chemistry and impurities

Long ago when I took chemistry courses in high school and lower, chemistry seemed so simple and elegant. All equations and exercises involved pure elements, pure compounds, with a very clean ...