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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964 views

Why add specifically hot solvent during recrystallization procedures instead of heating it up after?

Recrystallization methods that I have seen online and in manuals involve adding a minimum amount hot solvent to the solid mixture. Is there a reason I should do this instead of adding an equivalent ...
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Inorganic Exclusion Rate to Expect During Recrystalization?

In the following context, what approximate exclusion rate can I expect towards all combined inorganic ions (metals, ...) per recrystalization cycle? Can I expect it to radically evolve along the ...
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1answer
87 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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1answer
3k views

Tips for maximizing yield, purity and crystal size during recrystallization

I have already asked a similar question on titrations before. In a few months, I have a test on chemical synthesis. It is marked on the percentage yield, purity and crystal size of the product. I do ...
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1answer
444 views

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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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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1answer
68 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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1answer
68 views

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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1answer
457 views

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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2answers
7k 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 sample? As well as why is would be better 'technique' to allow for the crystal to form slowly? I was ...
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1answer
124 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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2answers
114 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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1answer
119 views

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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217 views

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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2answers
1k views

Potassium Alum Crystals

This is a question regarding the crystallization of $\ce{KAl(SO4)2 . 12 H2O}$. I have an idea of what to do (I'll explain later in the explanation), but I would like to hear other suggestions encase ...
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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?
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2answers
639 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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1answer
84 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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172 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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1answer
78 views

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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1answer
993 views

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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392 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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0answers
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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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50 views

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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1answer
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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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1answer
20k views

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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1answer
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Growing crystals that are in a magnetic field or subjected to an electric field

I know different crystals resonant at different frequencies but is it possible to grow crystal at a certain frequency. An example would be growing crystals using Epsom salt or Alum in a magnetic ...
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1answer
616 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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164 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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1answer
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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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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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2answers
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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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1answer
3k views

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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2answers
211 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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1answer
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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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1answer
850 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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1answer
485 views

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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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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1answer
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How to recrystallize boric acid into flakes?

I am putting 100 g of boric acid, 400 g of water and trying to crystallize at low temperature and letting cool slowly, however it recrystallizes as needle like texture. I need soft large crystals like ...
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3answers
27k 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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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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1answer
793 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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339 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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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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1answer
3k views

Why do we scratch the walls of test tube in test for magnesium or calcium basic radicals?

In test for calcium ion, we add ammonium carbonate in presence of ammonium hydroxide and then white precipitate (of $\ce{CaCO3}$) is formed which is dissolved in acetic acid and then reacted with ...
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1answer
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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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1answer
953 views

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 ...