1. Glass
The most wonderful properties of glass are transparency, no rust, corrosion resistance, these advantages are beyond the reach of other materials, such as a variety of excellent metals, masonry and wood. Glass necklace beads excavated from ancient Egyptian tombs have been buried in the ground for more than 4,000 years and still shine as beautifully as they were made back then.
The main component of glass is quartz stone, that is, silica (SiO2), which is very hard, in addition, it has transparent properties, it is widely used as window glass, optical instrument glass, and various chemical and living containers.
People's various experiments in chemistry always hope to directly see the chemical reactions in the container, which can only be done by glass, because it is transparent and resistant to the corrosion of various chemicals. Ordinary metals undergo chemical reactions when they encounter acid, and even the most stable "king of metals" gold is tamed and dissolved when it encounters "aqua regia" mixed with nitric acid and hydrochloric acid. Only glass is not afraid of hydrochloric acid, sulfuric acid, nitric acid and even aqua regia. Only caustic can slightly corrode a layer of the skin of the glass. As a result, glass has become the darling of chemists, and even become a "glass test tube expert" for chemists.
Glass is brittle but hard, and the pressure it is subjected to far exceeds that of pig iron. Someone has done such an experiment; Pressurize weights on pig iron blocks and glass blocks of the same size. When the weight reaches a hundred pounds, the pig iron block is crushed, while the glass is unharmed. It was pressurized until it was more than 180 pounds before the glass block broke.
In the face of such a hard temper, we can not move knives, scissors, cones, and saws made of ordinary steel, and only knives and gold steel grinding wheels made of high-grade alloy steel can make marks on the glass.
Glass is so hard, how can we easily process a variety of beautiful patterns on it? We don't need to rush, as the saying goes: brine points tofu, one thing descends one thing". There is an acid ---- hydrofluoric acid, but this chemical can easily subdue hard glass, and can "carve" beautiful patterns, characters and other patterns on glass, which is really a "carving" master.
Why does hydrofluoric acid have such a huge ability?
It turns out that fluorine is the most active non-metallic element. Fluorine and hydrogen can be easily combined to form hydrofluoric acid. Fluorine can react with almost all elements, hydrofluoric acid inherits its nature, but also has a strong corrosion, can react with most metals, non-metals.
When hydrofluoric acid encounters glass, it will chemically react with the chemical composition of the glass:
SiO2+4HF＝SiF4↑+2H2O
The main component of the glass, silica, reacts with hydrofluoric acid to produce volatile silicon tetrafluoride gas and water, so the glass is corroded and becomes frosted glass, which is the secret of carving.
Beautiful glass flowers have become a craft that adorns people's lives.
If people want to make the scale on the measuring cylinder and measuring cup, just put the measuring cylinder in the melted paraffin wax to dip, and then scrape the wax on the scale position vigorously, and then apply hydrofluoric acid (or put it in hydrogen fluoride gas) for corrosion. Since hydrofluoric acid can not chemically react with paraffin, only the glass engraved with paraffin on the measuring cylinder is corroded, so after removing excess hydrofluoric acid and paraffin, etched scale lines will appear on the measuring cylinder and other instruments, so the measuring cylinder is prepared.
Because hydrofluoric acid corrodes glass, hydrofluoric acid cannot be stored in glass bottles, but in polyethylene plastic bottles, and we can put it in copper vessels when we do experiments. Because copper utensils are corroded by hydrofluoric acid, a layer of lead fluoride PbF2 is formed on the surface to protect lead from corrosion.
We should pay attention to the fact that hydrofluoric acid is toxic, and the experiment must have ventilation conditions.
Second, the chemical composition of common jewelry
Jewelry is a general term for pearls and gemstones. Pearl is a beautiful small circle with luster gradually formed by the stimulation and secretion of nacre by sand microorganisms entering the shell of the shell, and the chemical composition is calcium carbonate and a small amount of organic matter, in addition to being used as an ornament, it also has medicinal value.
Gemstones generally refer to minerals with a hardness of more than 7 degrees, beautiful color, no chemical changes due to the action of the atmosphere and drugs, scarce yields, and extremely valuable minerals.
Excellent sexual such as: diamond, steel jade, beryl jade, precious garnet, tourmaline, precious opal, etc.;
Inferior qualities such as: crystal, chalcedony, agate, jasper, malachite, amber, garnet, opal, etc.
The chemical composition of some common gemstones is described below:
diamond
Also known as diamond, commonly known as diamond, diamond or rhinestone, the composition is C, is an allotrope of carbon, often colorless and transparent, hardness of 10, is the hardest of minerals. Artificially manufactured is also called synthetic diamond.
corundum
Transparent crystal, hardness of 9, second only to diamond, the main component is Al2O3, colorless, red, blue, star. Colorless and transparent is also called white jade; Those containing Ti4+ or Fe2+, Fe3+ blue are called green jade, also called sapphire; Those containing Cr3+ red are called carnelian, also called ruby; The star is also called the star gemstone.
beryl
Also known as chrysoprase, emerald. Transparent to translucent crystals, hardness of 7, mostly emerald green, light green, also colorless or blue, yellow, white, pink, the main component is 3BeO•Al2O3•6SiO2. Among them, those containing CrO3 are called beryls, also known as jade or emeralds; Iron-containing transparent blue is called aquamarine; Those containing cesium and have a rose color are called rose soul beryl.
topaz
Also known as citrine, similar in appearance to crystal, often yellow, transparent, hardness of 8, the main chemical composition is Al2SiO4(F, OH)2.
jadeite
Commonly known as jade with nephrite, the component is NaAl (SiO3)2, crystalline or dense block, thick green, light green or white, green is often called jadeite, slightly transparent, hardness of 6.5~7, more difficult to dissolve than nephrite. The composition of nephrite is Ca(Mg, Fe)3(SiO3)4, and the hardness is 5.5~6.
garnet
It is a fluorescent silicate, the composition is indefinite, there are the following formulas: 3RO • R2CO3 • 3SO2, where R represents calcium, magnesium, iron or manganese, but also represents aluminum, iron, chromium or cobalt, hardness of 6.5 ~ 7.5, transparent to slightly transparent, sometimes or photoabnormal, birefringence, color is generally beautiful. The composition of Fe3Al2Si3O12 is called garnet, often blood red or pink, and slightly black in appearance.
opal
Contains water, silica, hardness is inferior to quartz, the surface is often grape-like, white gray, yellow-brown and other colors, luster like fat or pearl, opaque to slightly transparent. If it is beautiful breast-like, often red or green, strong luster, the profile can show a variety of beautiful colors of reflection, often called precious opal.
crystal
Hexagonal columnar pure quartz crystal, colorless and transparent, large refractive index, which contains mechanisms and smokey ceramic color is called smoky quartz (commonly known as tea crystal), black is black smoky crystal (commonly known as ink crystal). Nitrogenous organic matter that is brown or yellow is called brown quartz or citrine. Those containing manganese and purple are called amethyst.
chalcedony
Transparent or translucent, the composition is SiO2, and the hardness is 7. There are flesh red, light red, thick green, blood red, etc., and the opaque one is agate.
jasper
It is deposited by siliceous substances, the chemical composition is SiO2, and contains Fe2O3, because it contains iron, so it often shows various colors. Its thick green is very similar to thick chrysoprase, dense and opaque,
amber
The composition is hydrocarbon (C10H16O), amorphous, transparent to translucent, russet and other colors, hardness of 2~2.5, friction energy to generate electricity.
malachite
The composition is Cu2(OH)2CO3, formed by the action of carbonic acid and water, the luster is diamond-like, the color is emerald green, and there is a peacock tail color twist
Third, the identification of real gold
With the continuous improvement of people's living standards, more and more people wear gold jewelry, when buying, people always want to buy pure, pure is called full gold is real gold.
Real gold shining, heavy, specific gravity 19.3 (g/cm3), not afraid of corrosion, thousands of years later its color does not change.
Although real gold is sparkling, it is not necessarily real gold that shines gold, such as fool gold and artificial imitation gold (such as titanium nitride, etc.). ）
Fool gold refers to the golden-yellow pyrite (FeS2) or chalcopyrite (CuFeS2) ore, which is often nicknamed for its charming appearance to fool people who lack mineral knowledge.
Fool's gold, imitation gold and real gold are no different, and it is difficult to distinguish between true and false. But as soon as they hit the touchstone, their "true face" was exposed. The touchstone is just a very common stone in nature, gray-black in color, shaped like a goose egg, and gradually turned into a goose egg due to weathering. During the test, as long as the test object is scratched on the touchstone, the original shape is revealed: the stripes drawn by pyrite are black; The streaks drawn by the chalcopyrite are dark green; And real gold? The scratches left on the touchstone are golden yellow again.
"Golden Footless Red". Natural gold is not absolutely pure, not to mention gold is rare, so many gold jewelry are added to the gold to make some copper and silver to make it into alloys. When people buy, this faces a problem of how to identify the purity of gold and determine its color (gold content).
With the "golden eye of fire" of the touchstone, it can not only distinguish the authenticity of gold; It can also identify the advantages and disadvantages of gold (in units of "K", in 24K... 100% is excellent; 18K... 75% are times; 12K... 50% is inferior) This is because gold jewelry of different colors has a slight difference in color.
Standard gold bars with different gold content are refined in advance according to the proportions, one by one the color marks of the known content are scratched on the touchstone, and then the gold jewelry to be tested is scratched on the same touchstone, and the two are compared, and finally the color is judged by experienced experts. This method is simple and easy, but there is a certain error, and it is necessary to find a more accurate method and choose a "sharper-eyed" instrument.
With the development of science and technology, a laser touchstone has been invented abroad. The laser beam irradiates gold, alloy or imitation gold, respectively into vapor, showing different spectral lines and their intensity, so as to identify correctly, simple operation, do not worry about the loss of gold, inspection, the traces of laser hitting are smaller than the tip of the needle, the sample loss is less than one billionth of a gram, it is really minimal, quite popular with customers and jewelers, this kind of instrument that opens all kinds of "Lushan true face" gold jewelry, can be called a veritable "touchstone".
Fourth, all kinds of pots
There are various pots in the kitchen: rice cooker, stir-fry pan, steamer, pressure cooker, milk pan, frying pan..., but from the perspective of raw materials for manufacturing, there are generally only two kinds of iron pots and aluminum alloy pots.
In the past, copper pans were also used. Humans discovered and used copper much earlier than iron, and it was natural to use copper to make pots first. After the emergence of iron pots, some people still prefer to use copper pots. Copper is shiny and looks aesthetically pleasing. Among metals, copper ranks second only to silver in its heat transfer capacity, which is better than iron. The biggest disadvantage of using copper as cooking utensils is that it is easy to produce toxic rust, which is what people call patina. In addition, the use of copper pans destroys vitamin C in food.
With the development of industry, people found that using copper to make pots was really wronged by it. The production of copper is not much, the price is expensive, used to make wires, make motors, and even make guns and bullets, can play its characteristics. Thus, the iron pot replaced the copper pan.
In the countryside, the cauldron on the stove is cast in pig iron. Pig iron is hard and brittle, and it will not deflated if you knock lightly, and it will break if you hit hard. Wrought iron can be used as a stir-fry pan and iron spoon. Wrought iron is soft and tough, and does not break. Iron pans are cheap. More than thirty years ago, the pots in the kitchen were almost all iron pots. The iron pot also has its disadvantages, which are bulky and easy to rust. The iron rusted, as if it had developed epileptic scars, and fell off one by one. Iron's heat transfer ability is not too strong, not only compared to copper, but also not as good as aluminum.
Now many of the utensils in the kitchen are aluminum or aluminum alloy products, pots, spatulas, spoons, almost all of aluminum alloy. However, a century ago, aluminum was more expensive than gold and was called "silver-white gold".
The French Emperor Napoleon III treasured a set of tableware made of aluminum, which was only taken out for a grand state banquet to show off. Mendeleev, a Russian chemist who discovered the periodic law of the elements, once received a high award from the Royal Society —— — an aluminum cup. These stories now sound laughable. Today, aluminum is a very cheap metal. Compared with iron, aluminum has strong heat transfer ability, light and beautiful. Therefore, aluminum is an ideal material for cookware.
Some people think that aluminum does not rust. In fact, aluminum is a lively metal, and it is easy to oxidize with the air to form a transparent, thin layer of aluminum rust - aluminum oxide. However, this layer of aluminum rust, unlike loose rust, is very dense, like skin to protect the inside from rust. However, this layer of aluminum rust film is afraid of both acid and alkali. Therefore, the time to store dishes in an aluminum pot should not be too long, do not use it to hold vinegar, sour plum soup, alkaline water and brine.
Aluminum alloy is smelted by adding a small amount of magnesium, manganese, copper and other metals to pure aluminum, and the corrosion resistance and hardness have been greatly improved. Pressure cookers and kettles made of aluminum alloy have been widely sold in the market. In recent years, electrochemical aluminum products have appeared in stores. This is the aluminum oxidized by the electrode, thickening the surface of the aluminum rust layer, while forming a loose and porous attachment layer, which can firmly adsorb the dye. Therefore, this kind of aluminum lunch box, rice pot, kettle, etc., the surface can be dyed with bright colors, making aluminum products more beautiful and endearing.
Aluminum pot also has its disadvantages, eating too much aluminum, easy to get Alzheimer's. So everyone better use a stainless steel pot.
In the countryside, it is also popular to serve wine in lead jugs. Everyone must pay attention to the fact that if you will have a stomachache after eating, the doctor may not be able to see the cause of your when you go to the hospital. In fact, this is called "lead poisoning".
Fifth, the magic of graphite
Everyone knows that pencils are used to write, but it has another trick - it can heal rusty locks.
The rusty lock cannot be opened, and adding a little pencil lead powder to the hole into the key can often open the rusty lock.
How can a pencil lead have such a trick? It turns out that the pencil lead contains graphite, and graphite has lubricity. Touching the powder of the pencil lead with your hand will give you a slippery feeling. Therefore, the pencil lead can lubricate the rusty lock.
The melting point of graphite is very high, reaching more than 3,000 degrees. As a lubricant, it is particularly suitable for machines working at high temperatures. At high temperatures, the general oil will decompose, however, graphite is "safe and sound" and continues to play a lubricating role.
There is a bearing that is molded with graphite powder added. This bearing can work for a long time without oil lubrication, and it has its own graphite as a lubrication. What an ingenious bearing.
On the door buttons of the helicopter cabin, new high-precision pure graphite bearings have been used in large quantities. This bearing is resistant to both low and high temperatures and, particularly impressively, maintains good lubricity under vacuum conditions.