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Dmitry Shintyakov
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It takes twice the man to ride half the bike
It takes twice the man to ride half the bike

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I thought that I have solid grasp of basic mechanics, but let me confess: I could not predict the outcome of this simple experiment.

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New crystals of sugar alcohol mannitol.
They are hard and brittle, making glassy sound if hit.

All crystals grown in 2 weeks from slightly supersaturated solution (several grams of additional compound per 100ml of solution).

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A successful experiment: by crystallizing a mixture of sodium and potassium ferrioxalates. I unexpectedly produced a compound with different crystal shape and (apparently) structure. Its stability to dehydration suggests that it is an anhydrous compound.
Literature gives formula K2.5Na0.5[Fe(C2O4)3], while my experiment suggests that K:Na ratio is closer to 2:1.

This is a test crystal, grown in 5 days. Will try to make a bigger one indeed.

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New crystal: ammonium alum with 10% of chromium ammonium alum, formula is

NH4 Al0.9 Cr0.1 (SO4)2 · 12H2O

it was grown using slow evaporation method, growth time is 2 weeks. To protect the crystal from dehydration and as safety measure, I covered it with a transparent layer of a pure ammonium alum, without chromium.


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Here are crystals of erythritol, grown in a month using slow evaporation method.

Crystal shape is complex, its base is flat rectangular prism with multiple additional facets on both bases. According to the literature, they have tetragonal symmetry.

Erythritol solubility in water at room temperature is around 50..60g/100ml (I don't have exact data). The method is:

* Prepare saturated solution:
* Dissolve 63g of erythritol in 100g hot water,
* Let it cool down to a room temperature. You'll get a slightly supersaturated solution.
* Put a few small crystals of erythritol in it and let it stay for a day. Crystals will grow and solution will become saturated.

* Attach a seed to a thin thread (I use nylon filaments), suspend it in the solution, and let it evaporate slowly. Over time, crystal will grow.

Clarity of the biggest specimen allows to observe unusual optical property of erythritol: birefringence. The strength of the effect depends on direction.


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Crystals of ammonium aluminum sulfate, also known as ammonium alum. The formula for this compound is NH4Al(SO4)2*12H2O

Crystals on the photo were grown in 6 months, using the usual slow evaporation method.

Chemically, this compound is very similar to the more well known potassium alum. It also crystallizes in large transparent octahedrons, but a bit more soluble: 15g/100ml versus 11g/100ml for potassium analog.

I have prepared it by mixing equimolar amounts of aluminum sulfate Al2SO4 and ammonium sulfate (NH4)2SO4.

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Sweet crystals of saccharin: artificial sweetener 300 times more sweet than sucrose.

Saccharin was the first successful chemical sugar substitute; it gained its popularity during the time of WW2 and is still in use nowadays, though to a much lesser extent: we have tastier and safer substitutes now.

Strictly speaking, saccharin is a weak acid, that is almost insoluble in water. Soluble saccharin is a sodium salt of this acid.

Sodium saccharin is well soluble in water (around 100g per 100ml), it easily forms large, well-formed crystals. Their shape is straight prism with rhombic base (this suggests orthorhombic crystal system, but I am not sure). My specimens were grown in 2 weeks, total mass of source compound was 18g.

Crystals are hydrated (sometimes this compound is referenced as dihydrate, though it is not exactly right). Exposed to dry air, they slowly dehydrate, losing transparency in several days, so they must be stored in a tightly closed container.

After growing the main specimens, I converted (by reacting with an acid) remaining compound into free saccharin, which is almost insoluble in water, and tried to make a crystal of it too. I have found that acetone is a good solvent for crystallizing it. Photos at the end show a small crystal of a free saccharin, grown from the acetone solution.

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Here are crystals of a double sulfate of zinc and potassium. Its chemical formula is K2Zn(SO4)2*6H2O, it belongs to a large family of double sulfates called Tutton's salts or schoenites. These compounds are water-soluble and very well suited for growing large crystals.

All crystals on this photo were grown in 1 month, using slow evaporation method ("glass and pencil" setup). They have the same base shape: slant prism with faceted corners.

There is a secret in getting very clear crystals of this compound: after preparing saturated solution, add baking soda (NaHCO3) to it, 0.5g of soda per 100g solution, and stir. The reaction will start, producing some gas (CO2) and sediment (mostly ZnCO3). Let it stay for a day, then filter the solution and use it for growing. The mechanism is not clear, presumably this removes impurities.

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New crystal of xylitol. I finally managed to make a completely clear sample.
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