Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [recrystallization]

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

2
votes
1answer
100 views
+50

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 ...
3
votes
1answer
42 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 ...
1
vote
0answers
27 views

Creating a pressure vessel to make emeralds and rubies/sapphires

So I understand that this is going to be a very difficult thing to properly do but I am looking to create a vessel for growing crystals. I am not looking to build a Verneuil furnace bit rather a ...
2
votes
2answers
108 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? ...
-1
votes
1answer
178 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 ...
1
vote
0answers
29 views

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, ...
0
votes
0answers
134 views

Why is recrystallisation used when filtration appears to be a better option?

Recrystallization: A solid containing the desired product and impurities are dissolved in a heated solvent. The reason this method works is because since the concentration of the desired product is ...
9
votes
1answer
1k 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 ...
3
votes
1answer
368 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 ...
1
vote
0answers
212 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 ...
4
votes
1answer
338 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 ...
3
votes
0answers
118 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 ...
3
votes
0answers
516 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 ...
1
vote
1answer
414 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 ...
1
vote
2answers
405 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 ...
1
vote
1answer
61 views

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 ...
0
votes
1answer
4k views

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 ...
2
votes
1answer
4k 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 ...
1
vote
1answer
205 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 ...
1
vote
1answer
630 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 ...
1
vote
1answer
154 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 ...
1
vote
0answers
27 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,...
5
votes
0answers
234 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? ...
0
votes
0answers
2k views

Which of the following solvent pairs could be used in a solvent pair recrystallization?

The question relates to the recrystallization of 4-bromoacetanilide using 1:9 ethanol. I feel like I a missing some important details. I used this for reference on a). What would be the most suitable ...
1
vote
1answer
3k 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 ...
3
votes
2answers
3k 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?
-1
votes
2answers
261 views

Making big crystals of oxalic acid crystals from powder [closed]

How to transform oxalic acid small crystals into large crystals?
4
votes
1answer
1k 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, ...
1
vote
1answer
7k views

What is the difference between hexanes and petroleum ether

I'm trying to use hexanes as the nonsolubilizing recrystallization solvent in a multisolvent recrystallization (benzene is the solubilizing solvent) that requires an oxygen free atmosphere and hexanes ...
5
votes
1answer
462 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 ...
2
votes
0answers
433 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 ...
5
votes
2answers
772 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 ...
2
votes
2answers
837 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 ...
1
vote
0answers
88 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) ...
0
votes
1answer
155 views

Crystallization Process

In my lab, my teacher asked me to not cover the beaker or crucible during the crystallization process of different solutions (e.g, FeSO4, NaCl etc). But on the internet, on Youtube, I've come across ...
3
votes
1answer
2k 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 ...
1
vote
1answer
119 views

Would a melted crystal recrystallize back into the same lattice structure when frozen?

Two things that I'm not sure about melted crystals: For a material that has only one possible crystal structure, would freezing cause it to recrystallize, or could it become amorphous upon freezing? ...
1
vote
0answers
46 views

Non-destructive solvents for cyan-salts

What dissolves cyan-salts (NaCN and KCN) without destroying them the way water does via hydrolysis? I have to make my own cyan-salts, so they're somewhat precious to me. Every time I have to ...
3
votes
1answer
1k 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 ...
1
vote
1answer
1k views

Tips for Improving Synthesis

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 ...
1
vote
2answers
389 views

Clarification on Recrystallization concept

Any help you could provide me would be greatly appreciated and I thank you for reading (even if you don't comment) I am in an organic laboratory and as a 3rd chemistry major these concepts usually ...
3
votes
1answer
160 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 ...
5
votes
1answer
1k 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 ...
3
votes
2answers
658 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 ...
5
votes
1answer
2k 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 ...
0
votes
3answers
18k 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 ...
3
votes
2answers
5k 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 ...
3
votes
1answer
1k 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 ...
0
votes
2answers
451 views

Best solvent for crystallization + mass recovered from crystallization + purity of the product

I have a chemistry final tomorrow and this question on my sample exam through me for a loop. I'm not entirely confident I can work out problems B and C, but those questions rely on the answer to A. ...
4
votes
1answer
321 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 ...