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ADSORPTION

 

With physico-chemical phenomenon, which now will be discussed, familiar to everyone, although maybe not all know what it is called adsorption. Even if you do not pass the adsorption on lessons, watched you many times. As soon as you put the ink blot on paper or, worse, on clothing, and are familiar with this phenomenon. When the surface of one substance (paper, fabric, and so on) absorbs particles of another substance (ink, etc.), this is adsorption.

A very good adsorbent is charcoal. Not stone, and wood, and not just wood, and active (activated). Such coal sold in pharmacies, usually in the form of tablets. With him and start experiments on adsorption.

Prepare pale solution ink of any color and pour into a test tube, but not the top. Put in a test tube tablet active carbon, better pounded, close your finger and shake as it should. The solution will brighten eyes. Adjust the solution to any other, but also painted - let it be diluted gouache or watercolor. The effect will be the same. And if you take just pieces of charcoal, they will absorb the dye is significantly weaker.

This is not surprising: the activated carbon is different from the usual because it has a much larger surface. Its particles are literally riddled with pores (coal treated in a special way and removed from impurities). And as soon adsorption is the absorption surface, it is clear: the larger the surface, and the absorption is better. Adsorbents capable of absorbing substances not only from solutions. Take a half-liter glass jar and put on the bottom of one drop of Cologne, or any other odorous substances. Grasp the Bank hands and hold her for half a minute to warm a bit odorous liquid - then it will quickly evaporate and stronger smelling. As is customary in chemistry, not sniff the substance directly from the flask, and light waves hands point to your nose air together with pairs of substances; not always know if the smell of the substance in the flask.

Whatever the smell, you will certainly feel clearly. Now put in the flask a little active charcoal, close it tightly with a lid and leave for a few minutes. Remove the cover and re-direct the air to yourself by waving palms. The smell disappeared. He was adsorbed by the adsorbent, or, more precisely, the absorbed molecules of volatile substances that you put in the Bank.

Not necessarily to take for these experiments, activated charcoal. There are many other substances which can serve as adsorbents: tuff, dry milled clay, chalk, blotting paper. In short, a variety of substances, but always with a developed surface. Including certain foods - you probably know how easy bread absorbs odors. No wonder wheat bread is not advisable to keep in one package with rye - their scents mixed together, and each loses its intrinsic flavor.

A very good adsorbent - popcorn, or corn sticks, much-loved by many of us. Of course, to spend on the experience of package or even a quarter of the package makes no sense, but a few pieces... will Try. Previous experience with odorous substances repeat in the presence of corn sticks - and the smell completely disappears. Of course, after the experience has sticks anymore.

Let us return to the experience with obtaining carbon dioxide (carbon dioxide). Fill out this two gas tubes, and in one place the corn sticks and shake a few times. Next, as before, repeat the experiment with lime water (you can just "pour" it gas from the tubes - it is heavier than air). Is there a difference in the behavior of lime water? Yes, it will. The liquid becomes turbid only glass, in which "poured" gas is not treated with the adsorbent. The other tubes that were corn sticks, carbon dioxide is not removed: it was swallowed by the adsorbent.

If you work in chemical circle and have learned to receive and collect such colored gases, such as chlorine and nitric oxide (home with them to have not just want good traction), you can experience them subject to coal and corn sticks. In a vessel with painted gas place the adsorbent, shake a few times and the color, if not disappear altogether, it will significantly weaken.

Now many kitchens over gas stoves put a variety of devices for cleaning air from Chad and smoke. In such devices, among other things, there is a cartridge with any adsorbent through which the drive polluted air. What happens, now you know. And when the entire surface is occupied by outsiders, "absorbed" from the air particles cartridge replace fresh.

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

 

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