Questions tagged [recrystallization]

For questions related to dissolving and subsequently precipitating as substance. The purpose may be for purifying, creating polymorphs, or other reasons.

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Recovery of Urea from aqueous solution [closed]

When adding Urea to water, the reaction is highly endothermic. I was playing with the idea of using that for a Desktop cooling system, but for that, I'd of course have to recover that Urea from the ...
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7 votes
5 answers
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How can I roughly measure a fraction of a gram?

My son got a crystal making kit (from a relative) and it lists seed crystal weights of 0.5g for a small crystal solution and 0.75 g for a large crystal solution. The trouble is I (his father) don't ...
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How do I crystallize Sodium Acetate w/o a crystal? [duplicate]

I made some sodium acetate. Definitely not pure or anything close. But I just did it as a quick experiment. Just some vinegar and baking powder. When I search how to make $\ce{NaOAc}$ crystals, people ...
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11 votes
3 answers
762 views

Why is it so difficult to crystallise anything in a glass capillary?

I'm talking about very fine glass capillaries with a diameter under 1 mm. I've found that if I carry out melting point analysis, the material in the capillary doesn't crystallise again. I did wonder ...
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6 votes
3 answers
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Why is sea salt coarse?

What makes sea salt coarser than other salt? I have tried checking online but no one seems to discuss this. It seems that the grain of sea salt is larger, but I don't understand since the salt is ...
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-3 votes
1 answer
295 views

Best solvent for recrystallization of acetanilide? [closed]

How would you recrystallize acetanilide using ethanol and hexanes? I know this compound is not soluble with the hexanes solvent. But, where would I include ethanol in the procedure? Would I heat up ...
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14 votes
1 answer
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What factors promote honey's crystallisation?

Honey is a complex mixture containing, probably, more than hundred compounds. I understand that the % of those components will affect the crystallisation. However, I am wondering what factors may ...
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2 votes
1 answer
167 views

How to read mutual solubility curves of salts with a common ion?

Came across a few graphs that represent the mutual solubility of two compounds in a solvent, for e.g., solubility of $\ce{KCl}$, and $\ce{NaCl}$ in $\ce{H2O}$. On these particular graphs, I can see $x$...
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0 votes
1 answer
176 views

How to differentiate hydrous and anhydrous compound? [closed]

For an experiment, my teacher gave me containers of hydrates and their corresponding anhydrous compounds, but I have a feeling that for one of the compounds she switched the hydrate and anhydrous ...
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1 vote
2 answers
277 views

If stirring negatively affects crystal purity, why is it so?

My Intellectual Expectations Intuitively, I would expect strong stirring to improve crystal purity during the process of crystalization. My rationale is that strong stirring would increase contact ...
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3 votes
1 answer
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Are precipitation and crystallization both analogous between Chemistry and Meteorology?

A comment under the Space SE question Is there really precipitation on Mars? Does frost count? brings up the use of the term "precipitation" in chemistry and we wonder if precipitation in ...
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3 votes
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How does a shock, such as the snap of the disk in a reusable hand warmer, trigger the re-crystalization of a supersaturated solution?

Reusable handwarmers are made of something dissolved nearly to its saturation point in hot water (Sodium Acetate in the case of HotSnapz) at a high temperature, and then cooled to a temperature at ...
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1 vote
1 answer
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Will these K-alum crystals combine into a "cohesive/well-glued" mass?

The attempt to make a single solid mass of K-alum, using over 125 grams of McCormick K-alum powder, has resulted, in less than 2 hours, in: So besides the growth around the loop of the seed "...
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-4 votes
1 answer
122 views

Potassium tetraoxalate preparation [closed]

How is potassium tetraoxalate produced industrially? In fact How I can limit the reaction of $\ce{H2C2O4}$ and $\ce{KOH}$? Or is there any other route for this purpose?
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Drying sodium tetraborate for use as a standard

I am currently attempting to purify technical grade sodium tetraborate decahydrate by recrystallization for use as a titration standard. I don't have a requirement for a specific grade or purity. I'm ...
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1 vote
1 answer
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How can I purify Ferric or Ferrous acetate with a very basic lab?

I’ve been trying to make Ferric acetate by mixing vinegar with steel wool and allowing it to react. The result is successful in dying leather or wood black and acting as a mordant. Theoretically there ...
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4 votes
0 answers
309 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 ...
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1 answer
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What is this copper compound I made?

I started with copper (II) sulfate solution left over from a recrystallization. I added sodium carbonate (definitely an excess) and about 200 of water and got a lot of bubbling. I heated it, for no ...
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-1 votes
2 answers
752 views

What happens if the filter paper in vacuum filtration is BIGGER than the buchner funnel diameter? [closed]

I’m wondering what would happen if the filter paper in a vacuum filtration process is bigger than the buchner funnel diameter? I mean would some differences occurs? Or would the whole experiment ...
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Why are colloidal dispersions stable? [closed]

Smaller particles in a colloidal dispersion are less stable than larger ones due to their higher surface to volume ratio. Therefore Ostwald ripening occurs, a process which promotes growth of larger ...
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Anhydrous Chromium Alum production

I recently started a small project of making home-made chromium alum crystals, as can be found on many sites, videos and recipes all around the internet. I tried calculating the amount of salt I ...
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0 answers
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Why does cobalt(II) chloride (CoCl2) crystal melts?

I made $\ce{CoCl2}$ crystals by making a concentrated solution. After the crystals formed I took them out of the solution for drying. After a time I noticed that they were still wet so I dried off ...
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-3 votes
1 answer
663 views

Lead nitrate and sodium iodide [closed]

As we know that if you mix lead nitrate and sodium iodide solutions together, a yellow precipitate forms. Can you maybe add nitrate in water that may or may not have lead in it and then mix it with a ...
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2 votes
0 answers
202 views

Could you form quartz crystals by melting and cooling sand very slowly?

Since glass is amorphous quartz and when you slow the cooling of something enough it will crystallize, couldn’t you melt $\ce{SiO2}$ (sand) and then very slowly cool it to cause spontaneous nucleation ...
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6 votes
1 answer
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Are electronic descalers a scam?

It seems there are some electronic kits sold around nowadays by major retailers (e.g., Home Depot and Amazon) claimed to remove built-up scale from water pipes. But, do they actually work? If so, ...
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Steps of crystallization

An excess of copper(II) oxide is added to dilute sulfuric acid to make crystals of hydrated copper(II) sulfate. The processes listed may be used to obtain crystals of hydrated copper(II) sulfate. ...
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30 votes
2 answers
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Is honey really a supersaturated solution? Does heating to un-crystalize redissolve it or melt it?

In the SciShow video Honey: Bacteria's Worst Enemy after about 00:30 the narrator says: Honey is only about 17% water. Most, but not all of what remains is sugar. ...
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6 votes
2 answers
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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 ...
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4 votes
2 answers
810 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 ...
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3 votes
1 answer
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Solubility of Potassium Dichromate in Water

According to Wikipedia, the solubility of Potassium Dichromate increases very significantly with the temperature. At 20°C, 13g/100ml, and at 100°C, 104g/100ml. Therefore, it should be possible to ...
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2 votes
2 answers
232 views

Does hydrazine crystallize when freezing?

When discussing problems of keeping hydrazine from freezing on spacecraft we stumbled upon a question: can pure hydrazine separate through fraction-freezing from the stabilizing substances like UDMH? ...
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-1 votes
1 answer
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How does recrystallization work to purify if compounds have equal solubilities, but one is present in a greater quantity?

Every article or text I've read on crystallization states that it works by taking advantage primarily of differences in solubilities, but I've also been told that it can purify compounds with ...
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1 vote
0 answers
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Readings about chiral resolutions at the undergraduate level

Does anyone know of a resource which clearly explains the scientific theory and experimental methods involved in chiral resolutions? I have access to the American Chemical Society, Tetrahedron, ...
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11 votes
1 answer
7k views

How to make pyramid-shaped NaCl salt crystals

I'm attempting to make sea salt pyramids like the one below. I understand this needs to be evaporated at a reasonable speed to stop the crystals forming a cube, as the when formed quickly, the edges ...
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3 votes
1 answer
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Questions regarding the preparation and recrystallisation of methyl 3-nitrobenzoate

I have a procedure for the synthesis of methyl 3-nitrobenzoate (via nitration of methyl benzoate): Weigh 2.0 g of methyl benzoate into a dry 50 cm3 conical flask. Add 4 cm3 of concentrated ...
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1 vote
0 answers
331 views

Multi-solvent recrystallization to extract solute from glycerol?

I have compound A contaminated with impurity B. Recrystallization in water would not yield pure compound A since impurity B is less soluble in it. The only solvent in which substances A and B have ...
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5 votes
1 answer
880 views

Crystallization of zinc sulfate monohydrate

I'm currently running an electrolysis experiment and I have a few questions regarding crystallization of zinc sulfate monohydrate $\ce{ZnSO4 * H2O}$. I have prepared a saturated solution of zinc ...
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2 votes
0 answers
358 views

What determines the maximum size of salt crystals as grown in flux growth?

Like many other children, I grew single crystal salt crystals in a salt solution. This is a common and fun experiment for children. However, with both this experiment, and with flux growth methods ...
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3 votes
0 answers
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Scratching the inside of a flask to crystallize aspirin - what is it called and has it been scaled up? [duplicate]

I've just watched the Periodic Table of Videos on Aspirin and saw some "tricks" used to induce crystallization after the synthesis. Rapid heating with a heat gun followed by rapid cooling in ice was ...
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1 vote
1 answer
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Crystallization in a solution of 2 or more solutes

This is a very basic question I found myself wondering. For simplicity's sake, we'll say it is a super saturated aqueous solution of an equivalent measure of sugar and salt. As the solution cools and ...
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1 vote
2 answers
1k views

Recrystallizing Sodium Acetate from solution

I made sodium acetate using the following reaction: $$\ce{NaHCO3 + CH3COOH ->CH3COONa + H2O + CO2}$$ The resulting solution of sodium acetate isn't pure, it has impurities. I want to crystallize ...
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1 vote
1 answer
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Determining the chemicals in potash and crystallizing them

I have made potash by leaching wood ash in water. The potash in solution has a high pH indicating it is alkaline, and reacts with acetic and citric acid. Is there an easy way to determine the ...
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0 votes
1 answer
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Solvent for recrystallization of benzoic acid?

Which is best solvent for recrystallization of benzoic acid? Water $\ce{CH3Cl}$ $\ce{CCl3COOH}$ $\pu{0.1 M}\ \ce{NaOH}$ I understand the solute/solvent should be soluble at high temperature, and ...
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3 votes
1 answer
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Why is the solid product washed with ice-cold solvent during in the last stages of recrystallisation?

Why is the solid product washed with ice-cold solvent during in the last stages of recrystallisation? Is this to remove soluble impurities? (for example) Well, what if the impurities were also ...
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1 vote
1 answer
1k views

Why is the addition of methanol during the prepartion of the liquid crystal cholesteryl benzoate necesary

Here's one way to prepare cholesteryl benzoate crystals: Step 1 Dissolve 1.0 g of cholesterol in 3 cm3 of pyridine in a conical flask. Step 2 Add 0.40 cm3 of benzoyl chloride. Step 3 Heat the ...
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1 vote
1 answer
1k views

Recrystallization Process Questions [closed]

Should a crude compound should be dissolved completely in cold solvent and then heated up? I think non-polar solvents are best choice for recrystallization of polar compounds, no? Recrystallized ...
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2 votes
1 answer
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DSC Metal hysteresis (melt/cryst)

So we were analyzing Polymers using DSC and calibrated the system using Indium. I expected it to be a single transition only as Indium only has 1 known crystal structure and as I never worked with DSC ...
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1 vote
0 answers
51 views

Pressure/ vacuum on preciptation of a borax saturated solution

Trying to go back to my collage chem/physics. We put a supersaturated solution of borax on the stove. (heated water, added borax till it would not take more borax). Placed them under vacuum 15 inhg,...
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6 votes
1 answer
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How do native sulfur crystals form?

I was visiting an elements exhibition in the Ulster Museum (Northern Ireland) and there were these native sulfur crystals on display. My question is how do sulfur crystals like these form in nature? ...
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2 votes
1 answer
7k views

Is it correct to say that SOME iodine undergoes sublimation at 1 ATM

The triple point of Iodine occurs at 0.12 atm and at standard temperature it is a solid on the phase diagram. I understand that therefore, when heating iodine at 1 atm, it (at least some of it) will ...
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