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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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31 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. ...
uhoh's user avatar
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26 votes
1 answer
8k 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 ...
Mad Scientist's user avatar
14 votes
1 answer
518 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 ...
Gonçalo Peres's user avatar
13 votes
1 answer
9k 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 ...
user57230's user avatar
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11 votes
3 answers
820 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 ...
BeginTheBeguine's user avatar
9 votes
3 answers
3k views

What is the correct name for this lab technique in crystallization?

Take a glass rod and rub vigorously the wall of the flask, the substance will crystallize out of the solution. Take a fire polished stirring rod and etch (scratch) the glass of your beaker. The small ...
Joseph's user avatar
  • 191
8 votes
2 answers
3k views

Saturation of multiple solutes

Can a liquid which is saturated with a single solute, dissolve a different solute, or is saturation a universal thing? I ask because I’ve seen that different solutes have different points (amounts) at ...
Yurelle's user avatar
  • 191
7 votes
5 answers
3k views

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 ...
user2617804's user avatar
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7 votes
1 answer
1k 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 ...
HaLo2FrEeEk's user avatar
7 votes
2 answers
5k 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 ...
Tan Yong Boon's user avatar
6 votes
3 answers
1k views

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 ...
Avrohom 's user avatar
6 votes
1 answer
2k views

Is it possible to separate salt from food, or at least convert it into something that doesn't taste salty?

A couple months ago, one of my room mates accidentally used a cup of salt to make apple crumble. She asked if there was any way to separate it, probably because I had recently reduced the acidity of a ...
Dan Ross's user avatar
  • 161
6 votes
1 answer
458 views

Can uranium be used to color aluminium oxide based gemstones, and/or diamonds?

Re-hosting this question from Physics to Chemistry, lightly edited. Rubies and sapphires are chemically equivalent to the mineral corundum, with the exception of transition metal impurities that ...
jpt4's user avatar
  • 69
6 votes
1 answer
2k 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 ...
Galen's user avatar
  • 673
6 votes
1 answer
5k views

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, ...
ManRow's user avatar
  • 1,546
6 votes
1 answer
720 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? ...
The Garage Chemist's user avatar
6 votes
1 answer
5k views

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 ...
Ramy's user avatar
  • 61
5 votes
1 answer
1k 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 ...
user50190's user avatar
5 votes
2 answers
2k 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 ...
Salicylica's user avatar
4 votes
1 answer
231 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 ...
uhoh's user avatar
  • 5,888
4 votes
2 answers
1k 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 ...
zetaprime's user avatar
  • 145
4 votes
1 answer
607 views

Why polymorphs form?

We always hear about the different arrangements of molecules that lead to the formation of polymorphs, my question here is why would a polymorph form in the first place? The material was given enough ...
Error404's user avatar
  • 283
4 votes
1 answer
3k views

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 ...
Mahbad Abdulla's user avatar
4 votes
3 answers
11k 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?
SinisterSine's user avatar
4 votes
0 answers
471 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 ...
Boo's user avatar
  • 71
3 votes
2 answers
2k views

Prevent crystal growth by adding a chemical to a solution?

If I have a solution of dissolved $\ce{NaCl}$ or sugar (or some other ionic compound), is there a chemical I could add to it that would prevent crystal growth if I boil it down? I'm looking for it to ...
Amber Goose's user avatar
3 votes
1 answer
4k 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 ...
Quark's user avatar
  • 946
3 votes
2 answers
2k 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 ...
Johnny Dollard's user avatar
3 votes
1 answer
5k 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 ...
Flyingfenix's user avatar
3 votes
1 answer
35k 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 ...
Mathematician's user avatar
3 votes
1 answer
3k views

Sublimation and recrystallization of caffeine

I'm looking to do an extraction of caffeine from energy drinks. I want to use both sublimation and recrystallization in my experiment for advanced purity. My question is which should happen first, ...
Rida's user avatar
  • 31
3 votes
1 answer
2k 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 ...
Pepria's user avatar
  • 567
3 votes
1 answer
4k 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 ...
Galen's user avatar
  • 673
3 votes
1 answer
2k views

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 ...
Rick T's user avatar
  • 386
3 votes
2 answers
8k 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 ...
Siddart Fredrick's user avatar
3 votes
1 answer
267 views

Crystallization issue

For solid-liquid mixtures, cooling crystallization process can be used to separate the solute substances from each other. Assume that we have two salts that have very close solubility in a certain ...
Pınar's user avatar
  • 303
3 votes
0 answers
2k views

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 ...
uhoh's user avatar
  • 5,888
2 votes
2 answers
314 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? ...
SF.'s user avatar
  • 641
2 votes
2 answers
2k 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 ...
Aeolus's user avatar
  • 405
2 votes
1 answer
2k 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 ...
Mathematician's user avatar
2 votes
1 answer
883 views

Crystallization of solutions and liquids

The process of crystallization of a liquid or any solute occurs when its concentration exceeds the maximum concentration which the solvent can carry or when the temperature drops below the freezing ...
stochastic13's user avatar
  • 6,805
2 votes
2 answers
2k 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 ...
QuarterShotofEspresso's user avatar
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 ...
Joseph Hirsch's user avatar
2 votes
1 answer
427 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 $x$...
nikhilelite 's user avatar
2 votes
1 answer
499 views

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 ...
Justanotherchemist's user avatar
2 votes
1 answer
10k 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 ...
Nanoputian's user avatar
  • 7,412
2 votes
0 answers
181 views

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 ...
eisd's user avatar
  • 148
2 votes
0 answers
394 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 ...
Quartz man's user avatar
2 votes
0 answers
404 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 ...
User2341's user avatar
  • 276
2 votes
0 answers
110 views

What do DNA crystals look like?

I had about 5 ug DNA suspended in water, which I dried thoroughly in a vacufuge. I obtained a whitish crystal (very similar to table salt, although the structure seems uneven and it's hard to tell) ...
Superbest's user avatar
  • 607