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CRYSTALS LARGE AND SMALL

 

About growing crystals written so much, and these experiments are so effective and easy-to-use, sure you set at least once and know what the principle is. Actually, nothing tricky here: it is necessary to prepare a hot saturated solution of any salt (sodium chloride, copper sulfate or iron, alum, potassium bichromate, and so on - the list is very large, gently to cool it, so the excess solute is not knocked out (such a solution is called supersaturated), and, finally, to enter the seed-crystal of the same salt, suspended by a thread. Then you just cover the container with a piece of paper, put it in a secluded place and wait until you grow a large crystal, which can take weeks or even months; only that it is necessary occasionally to do is pour a little saturated solution as evaporation.

All that is really known. But variants of the experience very much, and we will choose not the most common, for example, lead nitrate and potassium iodide. Mix equal volumes of 10%solutions of these salts, and the vessel will fall precipitate of iodide of lead. Carefully drain the fluid from it. Boil water in any transparent vessel, pocketlite her and vinegar until it boils, add the still moist precipitate of iodide of lead, usbatm it. At slow cooling fluid in it will grow Golden crystals.

A variation on the same theme: pour into a test tube solutions of lead nitrate and potassium iodide, boil the contents together with the sediment, so he dissolved, and then quickly cool under the tap. In this case produces tiny gold crystals suspended in liquid.

In General, the size of the crystals depends strongly on the cooling rate. Add 20 g of potassium nitrate in small portions in a container with 25 ml of water. After adding the next portion shake the mixture to dissolve the salt, and then pour the next batch. When the salt will no longer dissolve, slightly heat the vessel, pour another drink, shake, heat again. And so up until all taken salt are dissolved. Now pour the solution in two vessels, and one leave to cool in the air (for even more slow cooling, you can cover it with several layers of thick fabric). This vessel is formed by a few large crystals, and with luck - and a single crystal. Another vessel immediately put in a saucepan with cold water, and it will generate many small crystals. This General rule.

These two experiences are so impressive that they can show the audience, of course, careful preparing. The first is the experience of Pelago. Cylinder height 25-30 cm wash the inside with hot water and through the funnel on the wall, fill it with hot concentrated solution of hyposulphite, to fill the cylinder by 1/3. This solution is prepared: 450 g of hyposulphite dissolve when heated in 45 ml of water.

A second solution of sodium acetate (300 g in 45 ml of water) is also hot pour through the same funnel for another 1/3 of the cylinder. Pour very carefully, this solution should not be mixed with previously nality solution. Finally, the upper third of the cylinder so carefully fill with hot water, which will prevent a saturated solution from premature crystallization.

In a vessel of three layers: water, supersaturated solution of sodium acetate, supersaturated solution of hyposulphite. Cover with cylinder glass, allow to cool to room temperature, and then you can start to experience.

By the end of the glass rod attach a piece of wax small, inconspicuous crystal hyposulfite (wax slightly melt, heat it over the flame). In the eyes of the audience quickly dip the wand in the bottom layer. The salt concentration is so high that immediately around the crystal will pile up a lot of new crystals, forming a kind of flower. And in the middle layer "foreign" substance around crystal hyposulphite to crystallize will not.

Another, the exact same wand with wax, but with a small crystal of sodium acetate (audience shouldn't notice the difference) lower in the middle layer-here, too, will grow a flower, but very different! Cylinder, if you handle it carefully, it is possible to use several times.

A different experience, reminiscent of focus, with only one sodium acetate. Dissolve 100-150 grams of salt in hot water (preferably in enamelware) and slowly boil it put within, just trying to catch the moment when you need to stop evaporation: fan from time to time PA surface of the hot solution, and as soon as will receive the film, reminiscent of fat, it means that the concentration of salt that is required for the formation of crystalline structure CH3COONa*3H2o Pour the liquid into a clean thin glass, close it and put it to cool. In the cooled liquid enough to make a small number of seed - sodium acetate, so that it instantly secretaryshall and turned into a hard mass resembling ice. If you've nidderdale liquid fire and water it too much, over the solidified mass will be some water that must be drained. If there is not enough water on the surface will be a residue of salt. To remove it makes no sense, it's easier to add a little water.

Melting it in a water bath and cooling it, the experience can be repeated many times, including in the eyes of the astonished audience,and who would not be astonished to see how the water on the eyes freezes without cooling? On the contrary, the glass even warmed up is the heat of crystallization. The glass can be reversed, and it will not pour out a single drop.

Showing experience as the focus, try to shake off a grain of salt unnoticed - for example, with the tip of your magic wand." And be sure to tightly close the glass between experiments, or even a random speck of dust can cause unexpected crystallization.

The reagent for this experience - sodium acetate can be obtained from acetic acid and soda. If you cook it yourself, acetic acid, dilute with water about three times and pour it in the baking soda in small portions, gradually, so when it stops foaming from the previous serving of soda. Without this reaction will go so rapidly that the liquid can be thrown out of the vessel.

And even unusual crystals - metal. Will grow crystals of copper.

Small copper crystals you have already got, when I put a nail in a copper sulfate solution. They are so small that the film of copper on the surface seems to be almost continuous. And to make large crystals, it is necessary to slow down the reaction that would be emitted in the reaction of copper had time to settle to the crystals and built on them. Slow cooling is a possible way, but in that case, when there is a chemical reaction...

Brake for the reaction will serve as table salt. Put on the bottom of the vessel (for example, glass jars) a few crystals of copper sulphate and fill them with salt, if possible, fine. Cover them with a circle cut out of the blotting paper; this circle should touch the wall of the vessel. Top, right on the paper, put the iron circle slightly smaller diameter. Pre-wipe clean with abrasive paper and rinse.

Pour in the jar of a saturated solution of table salt, so that it completely covers the iron circle. Then everything will go without your participation. How long have to wait, you can't - a lot depends on the conditions of experience. Anyway, not an hour or two, and a few days.

So, a few days later you will find in the vessel a beautiful red crystals of copper. Changing the size of the vessel, the size of the crystals of copper sulphate, the thickness of the layer of salt and the temperature of the experience, mono to get copper crystals of various shapes, sometimes extremely unusual. And sometimes grow dendrites - unfinished in the development of crystals, similar to the branches of the trees.

If you leave the copper crystals in the same vessel in which they were received, how long they will not be saved. Remove them, rinse with water, transfer into a test tube with diluted sulfuric acid, and close the tube. Now with crystals nothing will happen.

O. Holguín. "Experiments without explosions"
M., "Chemistry", 1986

 

Your comments:

Dasha
2013-07-27 21:38:22
COOL YOU SHOULD TRY!
Daniel
2013-01-08 09:19:31
I made a solution of copper chuparosa
and forgot about it after a week the crystals to 2 cm long
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