The process of rendering something pure, clean of foreign or undesired elements.

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What makes oceanic desalination so expensive?

What specifically makes oceanic desalination so expensive?
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120 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 ...
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Comparing purity grades for ethanol

I am trying to determine if the following two grades of ethanol are equivalent: Ethanol absolute, 99.8% Normapur AR (Analytical Reagent) Ethanol alcohol, pure ACS reagent, ≥99.5% Information on ...
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How can I purify ethanol from formic / boric / salicylic acid?

I need some ethanol pure and strong enough for technical purposes (fuel, solvent, cleaning agent, dissolving rosin for soldering flux, etc.). Food quality is not required though, denaturated one is ...
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104 views

Old, red 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?
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45 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?
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28 views

Make pure phthalocyanines from phthalocyanine dyes

We need a pure copper phthalocyanine for our experiments. Of course, we can buy it from Sigma Aldrich, but this means we'll have to wait a while. In local area we can buy only dyes which are about 98% ...
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55 views

Is the following paragraph about steam distillation accurate?

I've been struggling with the various methods of purification of organic compounds. If a question comes up in my examination, asking me to explain steam distillation in my own words, I'd like to know ...
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65 views

How does the production of pure, crystalline silicon via the Czochralsky or Siemens process?

I have a few questions regarding the production of pure, crystalline silicon: As far as I know Silicon usually appears in nature in the form of sand or $\ce{SiO2}$ and then is split apart and brought ...
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58 views

Removing trace amounts of water from agricultural grade anhydrous ammonia

Agricultural grade anhydrous ammonia (liquefied gas) contains 2000 ppm $\ce{H2O}$. What would be the process to remove this water to obtain refrigeration grade (<100 ppm $\ce{H2O}$) anhydrous ...
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57 views

How to purify water with activated carbon?

If I am not mistaken, distilling water does not remove all possible impurities. Chemicals with boiling points less than $100\ \mathrm{^\circ C}$ will be transferred as well. Does the usual tap water ...
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64 views

How do I purify the resulting compound after a nitro- to amine-group reduction?

I have an aromatic compound that I reduced with either $\ce{Fe + HCl}$ or $\ce{Sn + HCl}$. How would you choose to go about extracting the compound? I'm thinking to dry off all the $\ce{HCl}$, ...
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766 views

What would be the most suitable solvent for a single-solvent recrystallization?

The compound in question is acetanilide, and the solvents in question are: water, ethanol, and ethyl acetate I was thinking all three would be suitable since upon experimentation, acetanilide ...
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377 views

Recrystallization and purification techniques for getting a pure sample

Could someone explain in detail as to why exactly recrystallization gives a more pure solid solid sample? As well as why is would be better 'technique' to allow for the crystal to form slowly? I was ...
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80 views

Chlorination of Water

Does passing chlorine gas through water form hydrochloric acid or bleach? Also, will a mixture of hydrogen and chlorine gas from electrolysis of brine do the same?
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378 views

How to obtain pure aniline from a mixture of phenol and aniline?

There is a mixture of aniline and phenol. I need to obtain (just the procedure) pure aniline. So I think the mixture should heat with Zn powder(to convert phenol to benzene) and then I thought to ...
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154 views

How to crystallize out reaction mixture from DMF?

Reaction was carried out in DMF, and TLC shows that the reaction has completed. But how to separate reaction mixture i.e. product from DMF? Edit Steglich Esterification was carried out and the ...
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78 views

Solar still and how it works

I use a solar still that holds 182 cubic feet of water. Here is how it works: There is an insulator on both sides of the metal bowl. On the outside it covers the whole thing. on the inside it covers ...
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165 views

Recrystallization of two unknown compounds?

I managed to separate a binary mixture(in solid form) of two unknown substances into two individual solid compounds. For the separation, I used an acid-base extraction with dichloromethane, NaOH, and ...
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277 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?
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What is a good way for a laymen to purify alcohol to near 200 proof?

I'm making herbal and medicinal mushroom tinctures and extracts. Normally I'll use everclear but it isn't cheap and 95% alcohol. Also I don't know what that other 5% is. Is it just water? Is ...
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97 views

Different techniques of distillations

I know that fractional distillation is used to separate two liquids that are miscible in one another and have close boiling points. However, I am really confused about vacuum and steam distillation - ...
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35 views

The proteins “eluted” or “were eluted”?

In describing proteins, I've written "the proteins detached from the [Ni-IDA] matrix and were eluted from the column" Should I use "were" or can something simply "elute" ?
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557 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 ...
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126 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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338 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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3k 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 ...
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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 ...
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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 ...
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386 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 ...
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189 views

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

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 ...
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67 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 $\ce{As_20_3}$, $\ce{As_2S_3}$, and $\ce{As_4S_4}$ are predominantly occurring in drinking ...
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160 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,
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355 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 the HCl, instead of getting a pink foamy substance I got a white ...
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167 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 ...
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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 ...
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449 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 ...
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366 views

Isolating salt from sea water using filters

Could a filter be used to isolating 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 ...
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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 ...
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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 ...
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128 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 ...
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431 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 ...
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Silver, its bactericidal features and 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: ...
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Are there any general rules for choosing solvents for recrystallization?

Recrystallization 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 ...
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How does Polytetrafluoroethylene (Teflon) differ from Polyvinylidene fluoride (PVDF) as a protein binding membrane material?

PTFE and PVDF (durapore) are both used in protein binding filter membranes (Millipore specifically). Chemically speaking the two polymers differ quite significantly due to the additional fluorides and ...