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SILVER MIRROR!

 

Is it possible? Mirror silver in special factories, workshops in the mirror. The craft is ancient, traditions and professional secrets - it's not easy to make a good mirror. And yet - will try!

Of course, the mirror surface can be prepared without difficulty,- reaction "silver mirror" put in the school lessons. But a good mirror will not work, will phoblastic a bit. No, here we will focus on this mirror. And it you will get if you will work carefully and not to neglect the little things.

Important warning: operate only with distilled water. Powder Crocus - specially prepared iron oxide (III)to sift through a fine sieve and the resulting dust dilute with distilled water. If you do not have "Crocus", you can take any finished polishing liquid, they are sold in hardware stores. Even the glass you're going to do the mirror, put it on the table. Check the level, whether horizontal surface of the table, and if not, put under the legs folded pieces of paper to flatten the surface. Do not take a large glass, best to start small. Not to accidentally crush it, put it on the table, for example, an old blanket.

Pour in the polishing liquid on the glass and carefully wipe it in a circular motion using felt, felt (you can take an old hat or a piece of soft leather. RUB the glass with gauze soaked in a suspension of finely milled and sifted pumice in water, again rinse with distilled water, wipe with a damp sponge, and then gauze swab dipped 0.15%solution of tin chloride (IV), again rinse and wipe wrung out tampon. Preparation of glass over. This is a very important procedure. From how well you did it, depends on the quality of the mirrors.

The treated surface should immediately be metal-plate. If for any reason you do not have time to prepare a solution for silver plating, then put the glass in warm distilled water and do not remove it until everything is ready. By the way, this operation is useful in all cases: well, if the glass degrees for 8-10 warmer than the solution for silver plating.

This solution should be prepared only in rubber gloves. It is obtained by mixing two solutions, each of which is prepared separately. We will indicate the amount of substance per liter of solution, and you think for themselves, how much solution you need.

First solution: 4 g of silver nitrate, 10 ml of 25%ammonia solution, 4 g of sodium hydroxide. The procedure for preparation of the solution not the usual. The entire silver nitrate dissolved in 300 ml of water, 9/10 solution pour into a clean beaker and add dropwise a solution of ammonia, all the while stirring the liquid with a glass rod. Turbid liquid will become more transparent, and, finally, the color will disappear. Add a little silver nitrate solution - the solution again becomes turbid. Add the sodium hydroxide solution, then the solution will take a light brown shade. Again dropwise add the ammonia solution, and the solution again will brighten, now he seems slightly bluish. Pour the remaining solution of silver nitrate and ammonia, as follows stir and top up with distilled water to liters.

If you have to store the solution, then pour it into a bottle or flask with a well-fitting stopper. Open-pan solution can not be stored!

Second solution: per liter of solution 100 grams of refined sugar and 10 ml of dilute (approximately 10%) sulfuric or nitric acid. Sugar pre-dissolve in distilled water, add the acid, will patipatti a quarter of an hour and add water up to a definite volume.

Mix two solutions: one ml of the second solution (with sugar) take about 100 ml of the first solution (with silver nitrate). The exact ratio will have to pick up on the experience. If there is an excess of sugar solution when the plating begins to fall, the flakes; if, on the other hand, this solution of the deficiency, the plating will go too slowly. The resulting mixture and quickly stir; she will become orange-red, and then turn black. This signal: it's time to start plating. Don't miss the moment!

Immediately pour the mixture on the glass. It will be spread over the entire surface, and the glass will become dark, but then quickly begins to brighten, it forms a layer of metallic silver, which is restored from nitrate. After 5-10 min, gently sleeves mixture from the glass with gauze (or even better - piece suede)dipped in distilled water, again pour the mixture and cook it for another quarter of an hour. Already they are vacuum surface rinse with distilled water. If the glass will be dark spots, they need to swab with a mixture of pumice, then a solution of tin chloride (IV), again pour on these places the mixture and rinse with water.

To check whether you have deposited silver on the glass, look through the mirror at a lamp power of 60 W - it should be just barely visible through the silvered glass.

The silver layer is still not firmly on the glass. To strengthen it, put a mirror in the vertical position for an hour or two to be heated at a temperature of 100-150°C. Use a drying Cabinet, at least - slightly-heated oven. When the mirror has cooled, cover with silver foil water-resistant clear varnish spray (brush it may cause damage). After drying, apply on top of the lacquer thick layer of opaque paint or black bituminous varnish. Slide the brush or spray from sprinklers only in one direction: either top to bottom or left to right.

The mirror is almost ready. Just need to tidy his face, poserebrennoi side. It can be leakages of silver; remove them with a swab moistened with a weak solution of hydrochloric acid. If you've contaminated hands, remove stains slightly warmed with a solution of hyposulphite and thoroughly wash your hands with warm water.

How many silver began to manufacture the mirror? And how much silver in this mirror? The questions seem simple, but answering them is not so easy. The silver film is so thin that even if you have a micrometer, not to measure...

So as not to spoil a good mirror, take some splinter, remove the layer of varnish and paint with cotton wool moistened with acetone, and put they are vacuum on the surface of a small crystal of iodine. Already at room temperature iodine quickly evaporates, its pair, filling the glass, because they are much heavier than air. That they are not dispersed randomly draught, cover the inverted crystal glass.

In the interaction of iodine with silver iodide is formed of silver, and near the crystal slowly dissolves transparent stain: iodide in a thin layer of transparent. And from the edges of the transparent spot silver film does not disappear, but becomes thinner. And as a result, the mirror appear colored rings, which can be seen particularly well in the reflected light.

Rings seem to be colored by the same reason we seem iridescent soap bubbles and oil spots on the water. This phenomenon is called interference of light in thin films, it is studied in the physics course. For us the most important is this: the more rings, the thickness of the silver film. If the film thickness of about 0.03 micrometers, three rings correspond to 0.06 micron, four - 0,09, five - 0,12, six - 0,15, seven of 0.21 μm.

Knowing the thickness of the silver layer, it is easy to calculate and the amount of silver: it is only necessary to multiply the thickness in the surface area and the volume received again be multiplied by the density of silver is 10.5 g/cm3).

Here is a benchmark for validation of calculation: the mirror area of about a square meter contains a little more than a gram of silver.

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

 

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