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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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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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 ...
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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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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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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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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 ...
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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 ...
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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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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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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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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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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 ...
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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 ...
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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 ...
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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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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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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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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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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 ...
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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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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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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 ...
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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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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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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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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 ...
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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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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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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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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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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, ...
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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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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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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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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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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 ...
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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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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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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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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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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 ...
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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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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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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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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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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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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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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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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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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) ...
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