There is a legendary story about the invention process of glass, a common building material in modern life:

On a sunny day a long time ago, a Phoenician merchant ship came to the mouth of the Bayrou River on the Mediterranean coast, carrying many crystals of natural soda. The crew don't know the law of sea water fluctuation here. The ship ran aground when it reached a beautiful sandbar not far from the estuary.

The Phoenicians trapped in the boat simply jumped off the boat of 1 and ran to this beautiful sandbar, enjoying themselves while waiting for the high tide to continue sailing. At noon, they decided to bury a pot on the sandbar to cook. But the sandbar is full of soft fine sand, and there is no stone to support the pot. Someone suddenly remembered the rock crystal soda on the boat, so everyone started work together, moved dozens of pieces to make a stove, and then set up firewood to burn it. Dinner will be ready soon. When they were ready to return to the boat after dinner, they suddenly found a wonderful phenomenon: I saw a crystal clear thing on the sand under the pot, which was very cute. Nobody knew what it was, so they thought they had found the treasure and put it away. In fact, when cooking with fire, the soda block supporting the pot reacts with quartz sand on the ground at high temperature to form glass.

The clever Phoenicians stumbled upon the secret and quickly learned how to make it. They first mixed quartz sand with natural soda, then melted it in a special melting furnace, and then made the glass liquid into large and small glass beads. These beautiful beads were quickly welcomed by foreigners, and some rich people even exchanged gold and jewels, which made Phoenicians rich.

Of course, it is difficult to verify the truth of this story, but in fact, as early as 2000 BC, Mesopotamia began to make simple glassware, and the real glassware appeared in Egypt in 1500 BC. Since the 9th century BC, the glass manufacturing industry has become increasingly prosperous. In the 6th century, glass factories appeared in Rhode Island and Cyprus. Alexandria, built in 332 BC, was an important city producing glass at that time.

Since the 7th century, the glass manufacturing industry in some Arab countries, such as Mesopotamia, Persia, Egypt and Syria, has also flourished. At that time, they were able to make lamps for mosques with transparent glass or stained glass.

In Europe, the glass manufacturing industry appeared relatively late. About18th century ago, Europeans bought high-grade glassware from Venice. A London businessman wrote in the letter 1669 sent to the Venetian glass manufacturer on September 7, "... we need flat glass very much. Please don't transport the packaged lens glass under the box with wine glasses! It is best to pack it carefully in one or two sturdy boxes ... "This situation gradually changed with the invention of an aluminum glass with better transparency by Crauste, a European crow, in the18th century, and the glass production industry flourished in Europe.

Glass is a kind of low-priced artificial gem, which is used to imitate natural jewelry and jade, such as chalcedony, timely, beryl (emeralds and aquamarine), jadeite, nephrite and topaz. Gemmology refers to the glass used to imitate precious stones, which consists of silicon oxide (a timely component) and a small amount of alkali metal elements such as calcium, sodium, potassium or oxides of lead, boron, aluminum and barium.

There are mainly two kinds of glasses as imitation gems: crown glass and flint glass. The most commonly used components of Guanpai glass are silicon, soda and lime, which are the same as those used to make bottles and optical glass. Besides containing silicon and soda, flint glass is also called lead glass, because lead oxide replaces lime in crown glass. Because of the existence of lead, its refractive index and dispersion are improved, so imitation gems made of flint glass are often very realistic. At the same time, trace elements can be added to the molten glass raw materials to make the glass show various colors, such as adding Mn to get purple, adding Co to get blue, adding Cr to get green, adding Cu to get red and so on.

Generally speaking, it is relatively easy to distinguish between glass and precious stones. Gemstones are all crystals, which transfer heat faster, while glass is amorphous without crystallization, which transfers heat more slowly. Therefore, when touching the sample by hand, natural gemstones have a cold feeling, while glass has a warm feeling. It is more sensitive to judge whether it is cold or warm with the tip of the tongue sample, yes. In addition, observing with a magnifying glass, there are often curved or swirling fine lines on the surface and inside of the glass, which looks like the phenomenon that honey or glue is mixed unevenly when it is poured into clear water. There are all kinds of bubbles in the glass, such as round beads, ellipses and flat beads, which can be easily observed with a magnifying glass. Therefore, anyone who sees the sample of the above phenomenon can conclude that it is glass rather than natural gem.

One of the cups

A solid amorphous glass mixture cooled by electrofusion. Generally brittle and transparent, the chemical composition is complex, and the main component is silicate.

Ordinary glass is made of soda ash, limestone, timely and feldspar as main raw materials, which are melted, clarified and homogenized in a glass kiln, then processed and shaped, and then annealed to obtain glass products. The main component of ordinary glass is roughly CaO∶Na2O∶6SiO2, which is a mixture of sodium phosphate, calcium silicate and silicon dioxide. Without a certain melting point, it softens in a certain temperature range and can be made into products of any shape after softening. In addition to ordinary glass, there are special glasses mainly made of borate, phosphate and fluoride.

If opacifying agents such as fluorite and calcium phosphate are added to the raw materials, opaque opaque glass can be made. For example, coloring agents such as cobalt oxide and nickel oxide are added to raw materials to make colored glass.

Tempered glass (quenched glass) can be made by heating ordinary glass to a soft temperature and then cooling it quickly and evenly. Its mechanical strength is 4 ~ 6 times higher than that of ordinary glass, and it is not fragile, so it becomes slag when broken, which is a kind of safety glass.

Glass is an important building material, which is also used for lighting and daily necessities.

The second cup

Glass production is a process of physical and chemical changes.

In glass production, the raw materials in the melting furnace have undergone complex physical and chemical changes after melting. Taking ordinary glass production as an example, the main reaction process is as follows:

At the beginning of heating, the powder began to dehydrate in the range of 100 ~ 120℃. At 600℃, limestone and soda ash produce double salts of calcium and sodium through the following reactions.

CaCO3+na2co 3 = sodium carbonate

At 600 ~ 680℃, the generated double salt begins to react with silica;

cana 2(CO3)2+2 SiO 2 = na 2 SiO 3+casio 3+2co 2↑

At 740 ~ 800℃, the low melting point mixture [Na2CO3-cana2 (CO3) 2] began to melt and continued to react with SiO2.

Sodium carbonate+sodium fluoride (sodium bicarbonate) 2+ silica

=2Na2SiO3+CaSiO3+3CO2↑

The reaction between calcium oxide melt and silicon dioxide begins at 890 ~ 900℃.

CaCO3+SiO2=CaSiO3+CO2↑

At 10 10℃, unreacted CaO also forms calcium silicate with SiO2 _ 2.

CaO+SiO2=CaSiO3

All the substances are melted at a temperature slightly higher than 1200℃, and glass is formed after cooling.

The third cup

Glass and glass products can be seen everywhere in people's daily life. No matter how different the appearance of these glass products is, they are all mixtures (supercooled liquids) composed of silicate with uncertain composition. Glass is generally transparent and fragile and has no fixed melting point. When it is heated, it usually changes from softening to completely liquid, and has a fairly wide temperature range. People use this property to make it into various shapes of utensils, handicrafts and so on under the condition of being semi-soft and not hard.

The most common glass is ordinary glass, that is, sodium glass, which is usually made by melting sand, soda ash and limestone. Its composition can be expressed by approximate chemical formula Na2CaSi6O 14 or Na2O CaO 6SiO2. Door and window glass and bottles made of it have long been familiar to people. If sodium carbonate in raw materials is partially replaced by potassium carbonate, potassium glass can be made. This kind of glass is hard in texture, high in temperature resistance, small in thermal expansion and cold contraction, and stable in chemical properties. Beakers, flasks, test tubes, burettes, etc. Most people in the chemistry lab use potassium glass. If sodium in glass is replaced by lead-containing compounds, lead glass can be made. Lead glass has high density and high refractive index, which can block harmful radiation and is suitable for optical glass and radiation-proof glass screens. In addition, if a small amount of colorant is added to the glass, colored glasses with different colors can be made. For example, adding copper oxide or chromium oxide can make green glass; Adding cobalt oxide can make blue glass; Adding zinc oxide or calcium fluoride can make milky white glass; Adding uranium-containing compounds can make yellow-green fluorescent glass; Adding colloidal selenium can make ruby glass; Colloidal gold can be added to make red, red, purple or blue glass.

With the development of science, all kinds of glasses with special functions have come out one after another. For example, the insulation effect of hollow glass with a thickness of several centimeters is equivalent to that of a brick wall with a thickness of more than 40 centimeters; Bulletproof glass is not afraid of shock and can prevent bullets; Fireproof glass can be flame retardant; Color-changing glass can adjust color with light intensity; Bioglass can be transplanted into human body instead of bone; A fine fiber glass can transmit tens of thousands of power supplies at the same time. These new glasses are playing an increasingly important role in people's production and life.