Oxides and hydroxides. Carbonates. Phosphates. Sodium bicarbonate: formula, composition, application Use of baking soda in everyday life
Baking soda, or baking soda, is a compound widely known in medicine, cooking and household consumption. It is an acidic salt, the molecule of which is formed by positively charged sodium and hydrogen ions, the anion of the acidic residue of carbonic acid. The chemical name of soda is sodium bicarbonate or sodium bicarbonate. The formula of the compound according to the Hill system: CHNaO 3 (gross formula).
The difference between acidic salt and medium
Carbonic acid forms two groups of salts - carbonates (medium) and bicarbonates (acidic). The trivial name for carbonates - soda - appeared in antiquity. It is necessary to distinguish between medium and acidic salts by names, formulas and properties.
Na 2 CO 3 - sodium carbonate, disodium carbonic acid, soda ash. Serves as a raw material for glass, paper, soap, is used as a detergent.
NaHCO 3 - sodium bicarbonate. The composition suggests that the substance is a monosodium salt of carbonic acid. This compound is distinguished by the presence of two different positive ions - Na + and H +. Outwardly crystalline white substances are similar, they are difficult to distinguish from each other.
The substance NaHCO 3 is not considered baking soda because it is taken internally to quench thirst. Although, using this substance, you can prepare an effervescent drink. A solution of this bicarbonate is taken orally with increased acidity of gastric juice. In this case, the excess of H + protons is neutralized, which irritate the walls of the stomach, cause pain and burning.
Physical properties of baking soda
Bicarbonate is a white monoclinic crystal. This compound contains atoms of sodium (Na), hydrogen (H), carbon (C) and oxygen. The density of the substance is 2.16 g / cm3. Melting temperature - 50-60 ° С. Sodium bicarbonate - a milky white powder - a solid fine-crystalline compound, soluble in water. Baking soda does not burn, and when heated above 70 ° C decomposes into sodium carbonate, carbon dioxide and water. In production conditions, granular bicarbonate is often used.
Safety of baking soda for humans
The compound is odorless and tastes bitter-salty. However, it is not recommended to sniff and taste the substance. Inhalation of sodium bicarbonate can cause sneezing and coughing. One application is based on the ability of baking soda to neutralize odors. Powder can be used to treat athletic shoes to remove unpleasant odors.
Baking soda (sodium bicarbonate) is harmless when in contact with the skin, but in solid form can irritate the eyes and esophagus. In low concentrations, the solution is non-toxic, it can be taken orally.
Sodium bicarbonate: compound formula
The gross formula CHNaO 3 is rarely found in the equations of chemical reactions. The fact is that it does not reflect the relationship between the particles that form sodium bicarbonate. The formula commonly used to characterize the physical and chemical properties of a substance is NaHCO 3. The mutual arrangement of atoms reflects the spherical-rod model of the molecule:
If you find out from the periodic system the values of the atomic masses of sodium, oxygen, carbon and hydrogen. then you can calculate molar mass substances sodium bicarbonate (formula NaHCO 3):
Ar (Na) - 23;
Ar (O) - 16;
Ar (C) 12;
Ar (H) -1;
M (CHNaO 3) = 84 g / mol.
Structure of matter
Sodium bicarbonate is an ionic compound. The structure of the crystal lattice includes the sodium cation Na +, which replaces one hydrogen atom in carbonic acid. The composition and charge of the anion is НСО 3 -. Upon dissolution, partial dissociation into ions occurs, which form sodium bicarbonate. The formula that reflects the structural features looks like this:
Solubility of baking soda in water
7.8 g of sodium bicarbonate are dissolved in 100 g of water. The substance undergoes hydrolysis:
NaHCO 3 = Na + + HCO 3 -;
H 2 O ↔ H + + OH -;
When summing up the equations, it turns out that hydroxide ions accumulate in the solution (weakly alkaline reaction). The liquid turns phenolphthalein pink. The color of universal indicators in the form of paper stripes in a soda solution changes from yellow-orange to gray or blue.
Exchange reaction with other salts
An aqueous solution of sodium bicarbonate enters into ion exchange reactions with other salts, provided that one of the newly obtained substances is insoluble; or a gas is formed, which is removed from the reaction sphere. When interacting with calcium chloride, as shown in the diagram below in the text, both a white precipitate of calcium carbonate and carbon dioxide are obtained. Sodium and chlorine ions remain in the solution. Molecular reaction equation:
Interaction of baking soda with acids
Sodium bicarbonate interacts with acids. The ion exchange reaction is accompanied by the formation of salt and weak carbonic acid. At the time of receipt, it decomposes into water and carbon dioxide (volatilizes).
The walls of the human stomach produce hydrochloric acid, which exists in the form of ions.
H + and Cl -. If sodium bicarbonate is taken orally, reactions occur in a solution of gastric juice with the participation of ions:
NaHCO 3 = Na + + HCO 3 -;
HCl = H + + Cl -;
H 2 O ↔ H + + OH -;
HCO 3 - + H + = H 2 O + CO 2.
Doctors do not recommend constantly using sodium bicarbonate with increased acidity of the stomach. The instructions for the drugs list various side effects daily and long-term intake of baking soda:
- increased blood pressure;
- belching, nausea and vomiting;
- anxiety, poor sleep;
- decreased appetite;
- stomach ache.
Getting baking soda
In the laboratory, sodium bicarbonate can be obtained from soda ash. The same method was used earlier in the chemical industry. The modern industrial method is based on the interaction of ammonia with carbon dioxide and the poor solubility of baking soda in cold water... Ammonia and carbon dioxide (carbon dioxide) are passed through the sodium chloride solution. Ammonium chloride and sodium bicarbonate solution are formed. When cooled, the solubility of baking soda decreases, then the substance is easily separated by filtration.
Where is sodium bicarbonate used? The use of baking soda in medicine
Many people know that the atoms of metallic sodium interact vigorously with water, even its vapors in the air. The reaction begins actively and is accompanied by the release of a large amount of heat (combustion). Unlike atoms, sodium ions are stable particles that do not harm a living organism. On the contrary, they take an active part in the regulation of its functions.
How is sodium bicarbonate, which is non-toxic to humans and useful in many respects, used? The application is based on the physical and chemical properties of baking soda. The most important areas are household consumption, food processing, healthcare, ethnoscience getting drinks.
Among the main properties of sodium bicarbonate is neutralization of increased acidity of gastric juice, short-term elimination pain syndrome with hyperacidity of gastric juice, gastric ulcer and 12 duodenal ulcer. The antiseptic effect of baking soda solution is used in the treatment of sore throat, cough, intoxication, motion sickness. The mouth and nose cavities, mucous membranes of the eyes are washed with it.
Various dosage forms of sodium bicarbonate are widely used, for example, powders that are dissolved and used for infusion. Prescribe solutions for oral administration by patients, wash the burns with acids. Sodium bicarbonate is also used to make tablets and rectal suppositories. The instructions for the preparations contain detailed description pharmacological action, indications. The list of contraindications is very short - individual intolerance to the substance.
Using baking soda at home
Sodium bicarbonate is an "ambulance" for heartburn and poisoning. With the help of baking soda at home, they whiten teeth, reduce inflammation in acne, rub the skin to remove excess oily secretions. Sodium bicarbonate softens water and helps to clean dirt from various surfaces.
If you hand wash woolen knitwear, you can add baking soda to the water. This substance refreshes the color of the fabric and removes the smell of sweat. Often, when ironing silk products, yellow marks from the iron appear. In this case, gruel from baking soda and water will help. The substances must be mixed as quickly as possible and applied to the stain. When the gruel dries, it should be brushed and the product rinsed in cold water.
In the reaction with acetic acid, sodium acetate is obtained and carbon dioxide is vigorously released, foaming the whole mass: NaHCO 3 + CH 3 COOH = Na + + CH 3 COO - + H 2 O + CO 2. This process takes place every time when baking soda is "quenched" with vinegar in the manufacture of fizzy drinks and confectionery products.
The taste of baked goods will be softer if you use lemon juice instead of store-bought synthetic vinegar. In extreme cases, you can replace it with a mixture of 1/2 tsp. citric acid powder and 1 tbsp. l. water. Baking soda with acid is added to the dough as one of the last ingredients so that the baked goods can be put in the oven right away. In addition to sodium bicarbonate, ammonium bicarbonate is sometimes used as a baking powder.
Lithium carbonate is a commercial product in the above methods of processing lithium-containing raw materials. An exception is the lime method. Lithium carbonate is used directly and, in addition, it serves as a source for the production of various lithium compounds, the main of which are hydroxide and chloride.
Obtaining lithium hydroxide. The only industrial method for producing lithium hydroxide is causticizing with lime in solution:
Li 2 CO 3 + Ca (OH) 2 → 2LiOH + CaCO 3 (36)
The following data on the solubility (20 ºС) of the components of reaction 34 (Table 5) show that the reaction equilibrium should be shifted to the right:
Table 5
| Compound | Li 2 CO 3 | Ca (OH) 2 | LiOH | CaCO 3 |
| Solubility, g / 100g H 2 O | 0,13 | 0,165 | 12,8 | 1,3 ∙ 10 -3 |
At the same time, from the data on the solubility in the system Li 2 CO 3 - Ca (OH) 2 - H 2 O at 75 ºС it follows that the maximum concentration of LiOH cannot be higher than 36 g / l, i.e. only dilute LiOH solutions can be obtained. The initial product for causticization is wet lithium carbonate. Lithium carbonate and calcium hydroxide are mixed in a reactor; lime is taken in the amount of 105% of theoretical. The reaction mass is heated to boiling. Then the pulp is defended and the clarified solution is decanted. It contains 28.5-35.9 g / l LiOH. The sludge (calcium carbonate) is subjected to a three-stage countercurrent washing for additional extraction of lithium. The basic solution is evaporated to 166.6 g / l LiOH. Then the temperature drops to 40 ºС. Lithium hydroxide is isolated in the form of monohydrate LiOH ∙ H 2 O, the crystals of which are separated from the mother liquor by centrifugation. To obtain a pure compound, the primary product is recrystallized. The output of lithium in the finished product is 85-90%. The main disadvantage of the method is the high requirements for the purity of the starting products. Lithium carbonate should contain a minimum amount of impurities, especially chlorides. The lime should be free of aluminum to avoid the formation of poorly soluble lithium aluminate.
Obtaining lithium chloride. The industrial method for producing lithium chloride is based on the dissolution of lithium carbonate or hydroxide in hydrochloric acid, and carbonate is usually used:
Li 2 CO 3 + HCl → 2LiCl + H 2 O + CO 2 (37)
LiOH + HCl → LiCl + H 2 O (38)
Technical carbonate and lithium hydroxide contain a significant amount of impurities that must be removed first. Lithium carbonate is usually purified by converting it into a highly soluble bicarbonate, followed by decarbonation and the release of Li 2 CO 3. After purification of lithium carbonate containing 0.87 g / l SO 4 2- and 0.5% of alkali metals, a product is obtained containing traces of sulfur and 0.03-0.07% of alkali metals. To purify the hydroxide, recrystallization or precipitation of Li 2 CO 3 by carbonization of the solution is used. A schematic diagram of the production of lithium chloride from carbonate is shown in Fig. 16.
Rice. 16. Schematic diagram of lithium chloride production
The process of obtaining lithium chloride is associated with two difficulties - evaporation of solutions and dehydration of salt. Lithium chloride and its solutions are highly corrosive, and anhydrous salt is highly hygroscopic. When heated, lithium chloride destroys almost all metals, except platinum and tantalum, therefore, equipment made of special alloys is used to evaporate LiCl solutions, and ceramic equipment is used for dehydration.
To obtain lithium chloride, wet carbonate is used, which is treated with 30% HCl. The resulting solution contains ~ 360 g / l LiCl (density 1.18-1.19 g / cm 3). A slight excess of acid is given for dissolution, and after stirring, sulfate ions are precipitated with barium chloride. Then the solution is neutralized with lithium carbonate and LiOH is added to obtain a 0.01 N solution in LiOH. The solution is boiled to separate Ca, Ba, Mg, Fe and other impurities in the form of hydroxides, carbonates or basic carbonates.
After filtration, a 40% LiCl solution is obtained, part of which is directly used, and most of it is processed into anhydrous salt. Anhydrous lithium chloride is obtained in a series-connected evaporation tower and a drying drum. The content of impurities in lithium chloride is given below (Table 6):
Table 6
| NaCl + KCl | 0,5 |
| CaCl 2 | 0,15 |
| BaCl 2 | 0,01 |
| SO 4 2- | 0,01 |
| Fe 2 O 3 | 0,006 |
| H 2 O | 1,0 |
| Insoluble residue | 0,015 |
Calcium ... What do you know about it? "This is metal" - only and many will answer. What calcium compounds exist? With this question, everyone will start scratching their heads. Yes, there is not much knowledge about the latter, and about calcium itself, too. Okay, we'll talk about it later, but today let's take a look at at least three of its compounds - calcium carbonate, hydroxide and bicarbonate.
1. Calcium carbonate
It is a salt formed by calcium and carbonic acid residue. The formula of this carbonate is CaCO 3.
Properties
It looks like a white powder, insoluble in water and ethyl alcohol.
Obtaining calcium carbonate
It is formed when calcium oxide is calcined. Water is added to the latter, and then carbon dioxide is passed through the resulting solution. The reaction products are the desired carbonate and water, which are easily separated from each other. If it is heated, then decomposition will occur, the products of which will be carbon dioxide and When this carbonate and carbon monoxide (II) dissolve in water, calcium bicarbonate can be obtained. If you combine carbon and calcium carbonate, the products of this reaction are also carbon monoxide.
Application
This carbonate is the chalk that we regularly see in schools and other primary and secondary educational institutions... They also whitewash ceilings, paint tree trunks in the spring and alkalize the soil in the gardening industry.
2. Calcium hydrogen carbonate
Is Has the formula Ca (HCO 3) 2.
Properties
It dissolves in water, like all hydrocarbons. However, he makes her tough for a while. In living organisms, calcium bicarbonate and some other salts with the same residue have the function of regulators of the constancy of reactions in the blood.
Receiving
It is obtained by the interaction of carbon dioxide, calcium carbonate and water.
Application
It is found in drinking water, where its concentration can be different - from 30 to 400 mg / l.
3. Calcium hydroxide
Formula - Ca (OH) 2. This substance is a strong base. In various sources, it can be called or "fluff".
Receiving
Formed when calcium oxide and water interact.
Properties
It is in the form of a white powder, slightly soluble in water. With an increase in the temperature of the latter, the numerical value of solubility decreases. It also has the ability to neutralize acids, with this reaction the corresponding calcium salts and water are formed. If you add carbon dioxide dissolved in water to it, you get the same water, and also calcium carbonate. With continued bubbling of CO 2, the formation of calcium bicarbonate will occur.
Application
They whitewash the premises, wooden fences, and also coat the rafters. With the help of this hydroxide, lime mortar, special fertilizers and silicate concrete are prepared, and carbonate concrete is also eliminated (soften the latter). By means of this substance, potassium and sodium carbonates are causticized, root canals of teeth are disinfected, leather is tanned and some plant diseases are cured. Calcium hydroxide is also known as food supplement E526.
Conclusion
Now do you understand why I decided to describe these three substances in this article? After all, these compounds "meet" among themselves during the decomposition and receipt of each of them. There are many other related substances, but we'll talk about them another time.
Sodium belongs to alkali metals and is located in the main subgroup of the first group of PSE them. DI. Mendeleev. At the external energy level of its atom, at a relatively large distance from the nucleus, there is one electron, which the atoms of alkali metals give up quite easily, turning into singly charged cations; this explains the very high chemical activity of alkali metals.
A common method for producing alkaline salts is the electrolysis of molten salts of their salts (usually chlorides).
Sodium, as an alkali metal, is characterized by low hardness, low density and low melting points.
Sodium, interacting with oxygen, forms mainly sodium peroxide
2 Na + O2 Na2O2
By reducing peroxides and superoxides with an excess of an alkali metal, an oxide can be obtained:
Na2O2 + 2 Na 2 Na2O
Sodium oxides interact with water to form hydroxide: Na2O + H2O → 2 NaOH.
Peroxides are completely hydrolyzed by water with the formation of alkali: Na2O2 + 2 HOH → 2 NaOH + H2O2
Like all alkali metals, sodium is a strong reducing agent and interact vigorously with many non-metals (with the exception of nitrogen, iodine, carbon, noble gases):
Reacts with nitrogen extremely badly in a glow discharge, forming a very unstable substance - sodium nitride
It interacts with dilute acids like an ordinary metal:
With concentrated oxidizing acids, reduction products are released:
Sodium hydroxide NaOH (caustic alkali) is a strong chemical base. In industry, sodium hydroxide is obtained by chemical and electrochemical methods.
Chemical methods of obtaining:
Lime, which consists in the interaction of a solution of soda with lime milk at a temperature of about 80 ° C. This process is called causticization; it follows the reaction:
Na 2 CO 3 + Ca (OH) 2 → 2NaOH + CaCO 3
Ferritic, which includes two stages:
Na 2 CО 3 + Fe 2 О 3 → 2NaFeО 2 + CО 2
2NaFeО 2 + xH 2 О = 2NaOH + Fe 2 O 3 * xH 2 О
Electrochemically, sodium hydroxide is produced by electrolysis of solutions of halite (a mineral consisting mainly of sodium chloride) with the simultaneous production of hydrogen and chlorine. This process can be represented by the summary formula:
2NaCl + 2H 2 О ± 2- → H 2 + Cl 2 + 2NaOH
Sodium hydroxide reacts:
1) neutralization:
NaOH + HCl → NaCl + H 2 O
2) exchange with salts in solution:
2NaOH + CuSO 4 → Cu (OH) 2 ↓ + Na 2 SO 4
3) reacts with non-metals
3S + 6NaOH → 2Na 2 S + Na 2 SO 3 + 3H 2 O
4) reacts with metals
2Al + 2NaOH + 6H 2 O → 3H 2 + 2Na
Sodium hydroxide is widely used in various industries, for example, in the cooking of cellulose, for saponification of fats in the production of soap; as a catalyst for chemical reactions in the production of diesel fuel, etc.
Sodium carbonate It is produced either in the form of Na 2 CO 3 (soda ash), or in the form of crystalline hydrate Na 2 CO 3 * 10H 2 O (crystalline soda), or in the form of bicarbonate NaHCO 3 (baking soda).
Soda is most often produced using the ammonia-chloride method, based on the reaction:
NaCl + NH 4 HCO 3 ↔NaHCO 3 + NH4Cl
Many industries consume sodium carbonates: chemical, soap-making, pulp and paper, textile, food, etc.
Oxides
Quartz(SiO 2). Simple oxide of magmatic origin, resistant to weathering. Quartz is found both in crystalline and cryptocrystalline form (continuous granular masses), as well as crystal intergrowths (rock crystal). The color of the granular masses of quartz is different: colorless, smoky, yellow. The luster is glassy, greasy in the fracture. Cleavage is absent or very imperfect; fracture is concave. Transparent. Hardness 7, density 2.65.
The following most important varieties of crystalline quartz are distinguished: rock crystal - colorless, transparent; amethyst - purple; rauchtopaz - smoky, grayish or brown; morion - black; citrine - golden or lemon yellow. Quartz is included in granites, pegmatites, gneisses, shales, sands and clays. It dissolves only in hydrofluoric and phosphoric acids. It has four varieties - chalcedony, jasper, flint, agate.
Quartz is used in radio engineering (piezoelectric effect), in jewelry, in optics, for the production of durable refractory and acid-resistant glass.
Chalcedony(SiO 2). Painted in a variety of colors and shades: gray (chalcedony); yellow, red, orange (carnelian); brown and brown (sarder); green (plasma); apple green due to the presence of nickel (chrysoprase); green with bright red spots (heliotrope), etc. Luster is waxy, fractured, cleavage is absent. Hardness 6.5-7. Often forms pseudomorphs; known in drip forms.
Jasper(SiO 2, the ancient name "jasper"). Dense sedimentary siliceous rock. It is composed mainly of chalcedony and quartz with an admixture of iron oxides. Painted in a wide variety of colors: red, green, yellow, black, orange, bluish-green, etc. Hardness 6-7, matte gloss, uneven fracture. It is used in artistic and decorative items.
Flint(SiO 2). It consists of 96-98% chalcedony. This is chalcedony, contaminated with an admixture of clay and sand. The color is gray, brown and yellow. Gloss is matte, cleavage is absent, fracture is concave. Hardness 2.5.
Agate(SiO 2, onyx). Consists of chalcedony. It has a variety of combinations of shades: black and white (onyx), brown and white (sardonyx), red and white (carnelian onyx), gray and white (chalcedonyx). Luster is waxy, cleavage is imperfect, fracture is uneven. Hardness 6.5-7. Used in precision instrumentation.
Corundum(Al 2 O 3). Usually forms good barrel-shaped, pyramidal, columnar and lamellar crystals of trigonal system. Sometimes it forms solid granular masses. The color is usually bluish or yellowish gray; but there are also transparent crystals (blue are called sapphires, red - rubies). Glass luster, no cleavage. Fine-grained masses of corundum are called emery. Hardness 9, density 3.95-4.1.
Sometimes corundum is found in igneous rocks and pegmatites, but usually forms as a result of metamorphic processes in limestones and clay rocks. It is widely used as an abrasive in the metalworking industry, for processing optical glass, in stone cutting. Rubies and sapphires are precious stones.
Magnetite(Fe 3 O 4). Complex oxide (FeO · Fe 2 O 3). It is often found in well-octahedral crystals, but is usually distributed in continuous granular masses and in the form of inclusions in igneous rocks. The color is yellow-black, the line is black. Semi-metallic gloss, opaque. Cleavage is absent, highly magnetic. Hardness 5.5-6.5, density 4.9-5.2.
Magnetite forms under reducing conditions and is found in a wide variety of types of deposits and rocks. Used as iron ore. Iron contains 72%.
Hematite(Fe 2 O 3, red iron ore). The name comes from the Greek word "hema" - blood. It is found in the form of continuous dense shell-like granular and scaly masses, sometimes in the form of tabular crystals. The color changes from red to dark red and black. The line is cherry red. Semi-metallic luster, no cleavage. Hardness 5.5-6.5, density 4.9-5.3. Formed under the same conditions as magnetite. used as an ore for iron. Iron contains about 70%.
Hydroxides
Bauxite(Al 2 O 3 · nH 2 O). The name comes from the village of Beaux in Provence (France). It consists of several minerals hydrargillite Al (OH) 3, diaspora and bomite AlO (OH), as well as kaolinite, silica and iron oxides. Therefore, bauxite should be considered as a rock of sedimentary origin. The color is more often red, brown, less often pink, white. Matte gloss, amorphous structure, earthy fracture. The hardness is 1-3, in the most dense varieties it reaches 6. The origin is exogenous. Bauxite is an ore for aluminum production.
Limonite(2Fe 2 O 3 3H 2 O, brown iron ore). Usually contains impurities SiO 2, phosphorus. It got its name from the Greek word "lemon" - meadow (meadow, bog ore). It is found in continuous spongy masses in the form of drips and in earthy masses. The color of the incrustations is dark brown to almost black, the earthy varieties are ocher yellow and brownish yellow; the devil is yellowish-brown.
Limonite is a mixture of earthy minerals goethite (HFeO 2) and lepidocrocite (FeOOH), it is also closer to sedimentary rocks. Hardness 1 - in loose and earthy, up to 5 - in dense varieties, density 2.7-4.3. The origin is exogenous. It is formed during the decomposition of iron-containing minerals, as well as in the form of chemical and biochemical sediments on the bottom of lakes and the coastal part of the seas. Limonite is used as an ore for iron and for obtaining ocher - a base for water and oil paints.
Opal(SiO 2 · nH 2 O). Translated from the Sanskrit language, "upola" is a precious stone. Solid silica hydrogel with a water content of up to 3-9%, amorphous. Usually forms drip dense masses, composes skeletons and shells of some organisms (diatoms, radiolarians, etc.). colorless, but due to impurities it is colored yellow, brown, red, green and black. Semitransparent, fractured. Hardness 5.5, density 1.9-2.3. Glass luster. It is formed during the weathering of silicates and aluminosilicates, and also accumulates on the seabed as a result of the biological activity of marine organisms. The strata of opokas, tripoli, diatomites, and radiolarites consist mainly of opal. There is woody opal (petrified wood) - a pseudomorphism of opal on wood. It is used as an ornamental and precious stone, as an abrasive for polishing metals, stones, as well as for the manufacture of filters, refractory bricks, ceramics, etc.
Carbonates
These include about 80 minerals of carbonic acid salts (H 2 CO 3), which make up about 1.7% of the mass of the earth's crust.
Calcite(CaCO 3, lime spar). It crystallizes in the form of rhombohedrons and scalenohedrons, but more often it occurs in the form of various granular, earthy aggregates and sintered forms. The color is milky white, yellowish, gray, sometimes pink and blue. Glassy, transparent luster. Hardness 3, density 2.7. Cleavage is perfect. Boils violently with HCl with the evolution of CO 2. The transparent, colorless calcite crystals (rhombohedrons) are called Icelandic spar. They are birefringent.
Calcite is formed mainly from aqueous solutions both inorganic (tuff) and biogenic (limestone). This is due to the processes of chemical weathering and the activity of marine plants and invertebrates.
Calcite mixed with clay mineral forms strata of marls. Ground waters carry significant masses of calcium bicarbonate, forming in caves bizarre sinter forms of calcite in the form of stalactites and stalagmites. During the metamorphism of chalk, limestone and marl, strata of marble, consisting mainly of calcite, are formed.
The practical application of calcite is very diverse: it is used as a construction and ornamental material as a flux in metallurgy. Icelandic spar is used in optics.
Dolomite(CaMg 2). The name is given in honor of the French mineralogist Dolomier. Usually found in dense marble-like masses and very rarely in crystals. Painted in white, yellow and gray. Cleavage is perfect in three directions. Hardness 3.5-4, density 2.8-2.9. Glass luster. Reacts with HCl in powder. It is formed exogenously in water basins as a product of calcite change under the action of magnesian solutions.
It is used as a building and facing stone, as a refractory material and as a flux in metallurgy to obtain magnesium carbonate.
Siderite(FeCO 3, iron spar). The name comes from the Greek word "sideros" - iron. Forms continuous marble aggregates and spherical nodules, also occurs in the form of crystal intergrowths. The color is gray, brown, slightly pea. Glass luster, perfect cleavage. Hardness 3.5-4.5, density 3.7-3.9. Reacts with HCl when heated. It is formed both during an endogenous process (satellite of sulfides) and during exogenous processes (nodules and globular nodules in sedimentary rocks). Used as an ore for iron.
Phosphates
These include about 350 minerals of salts of phosphoric acid (H 3 PO 4) and make up about 1% of the mass of the earth's crust.
Apatite(Ca 5 3 (F, Cl)). The name comes from the Greek word "apato" - I'm deceiving, because for a long time it was mistaken for other minerals. It crystallizes in the hexagonal system in tabular hexagonal, prismatic and needle-like crystals. Often forms continuous masses of granular-crystalline structure. The color is white, green, blue, yellow, brown, sometimes colorless violet. Glassy, fragile luster. The fracture is uneven, the cleavage is imperfect. Hardness 5, density 3.2. The origin is endogenous; large accumulations of apatite ores are found in basic igneous rocks.
It is used as a fertilizer, in match making and in the ceramics industry.
Phosphorite the composition is similar to apatite. Contains a large amount of impurities in the form of quartz, clay, calcite, oxides and hydroxides of iron and aluminum, organic substances. It is closer in composition to sedimentary rocks. It occurs in the form of nodules, all kinds of pseudomorphs on various organic remains, in the form of nodules, plates, layers. The structure is amorphous. The color is black, dark gray, gray, brown, yellowish brown. Matte gloss. Hardness 5. When rubbed, emits a sulfur, garlic or burnt bone odor. The origin is exogenous. Used as a phosphorus fertilizer.
Silicates
Silicates are minerals that are extremely widespread in nature and often have a very complex chemical composition. They make up about a third of all known minerals and about 75-80% of the mass of the entire earth's crust. Many silicates are the most important rock-forming minerals, many are valuable mineral raw materials (emeralds, topazes, aquamarines, asbestos, kaolin, etc.). By X-ray studies, it was possible to establish that the main structural unit of all silicates is the silicon-oxygen tetrahedron 4-, silicon is in the center, and oxygen ions are located at four vertices.
Depending on the nature of the articulation and the location of the silicon-oxygen tetrahedra, the types of structures are distinguished: island, ring, chain (pyroxenes), tape (amphiboles) and frame silicates (feldspars, feldspatids). The formation of silicates is associated with endogenous processes, mainly with the crystallization of cooling magmatic melts.
Island silicates
These silicates are called island silicates because the silicon ion is located in the center, "on the island", surrounded by four oxygen ions. free valences are replaced by metal cations Ca, Mg, K, Na, Al, etc. Island silicates can also have more complex radicals by combining several tetrahedrons through oxygen.
Olivine((Mg, Fe) 2, peridot). The name comes from the olive green color of the mineral. Crystallizes in the rhombic system. Well-formed crystals are rare, more often found in granular aggregates. The color can vary from light yellow to dark green and black, but colorless, completely transparent crystals are not uncommon. Glass luster, imperfect cleavage. The fracture is shell-like, fragile. Hardness 6.5-7, density 3.3-3.5. The origin is endogenous. It occurs in ultrabasic (dunites, peridotites) and basic (gabbro, diabase, and basalt) igneous rocks. Unstable, decomposes with the formation of minerals: serpentine, asbestos, talc, iron oxides, hydromica, magnesite, etc.
Low-iron pure olivine rocks are used to make refractory bricks. Transparent olivine crystals of beautiful green color (chrysolites) are used as precious stones.
Pomegranates. The name comes from the Latin word "granum" - grain, and also from the similarity with the grains of the pomegranate fruit. They combine a vast group of cubic minerals with a characteristic crystal shape - perfectly faceted polyhedrons (rhombic dodecahedrons, sometimes in combination with tetragon-trioctahedra). Various colors (except blue). Glass luster. The line is white or light-colored in different shades. Cleavage is imperfect. Hardness 6.5-7.5, density 3.5-4.2. The most widespread are:
Pyrope - Mg 3 Al 2 3 dark red, pinkish red, black;
Almandine - Fe 3 Al 2 3 red, brown-red, black;
Spessartine - Mn 3 Al 2 3 dark red, orange-brown, brown;
Grossular - Ca 3 Al 2 3 copper-yellow, pale green, brown, red;
Andradite - Ca 3 Fe 2 3 yellow, greenish, brown-red, gray;
Uvarovite - Ca 3 Cr 2 3 emerald green.
Garnets are formed during metamorphism (in crystalline shales), in contact of felsic magmas with carbonate rocks, and sometimes in igneous rocks. Due to chemical resistance, they often turn into placers. Transparent varieties of almandines, pyropes, andradites are used as precious stones. Opaque garnets are used in the abrasive industry.
Topaz(Al (OH, F) 2). The name of the mineral comes from the name of the island of Topazos in the Red Sea. Crystallizes in the rhombic system. It is found in prismatic crystals with perfect cleavage. Crystals are usually colorless or blue, pink and yellow. Hardness 8, density 3.4-3.6 crystals are usually colorless or colored in blue, pink and yellow. new, pyrope, andradite are used as dragots. Glass luster. Occurs in felsic igneous rocks and pegmatites. Easily pass into placers.
Topaz is used both as a form and as a material for supporting stones, thrust bearings and other parts of precision instruments. Transparent topaz is cut like precious stones.
Sfen(CaTi × O, titanite). In Greek, "sphene" is a wedge, since the crystals are wedge-shaped. The color is brown, brown, golden. Brilliance is diamond. Hardness 5.5. The origin is endogenous and metamorphic. Used as an ore for titanium.
Ring silicates
Silicon-oxygen tetrahedra are connected in rings of three, four, six tetrahedra.
Tourmaline((Na, Ca) (Mg, Al)). Crystallizes in the trigonal system in the form of elongated prisms. The color is dark green, black, brown, pink, blue, there are colorless differences. Glass luster, no cleavage. Hardness 7-7.5, density 2.98-3.2. It is found in granites, pegmatites, as well as in shales and zones of contacts with igneous rocks. It is used in electrical engineering (piezoelectric effect) and in jewelry.
Beryl(Be 2 Al 2). The system is hexagonal, found in hexagonal prisms. The color is yellowish and emerald green, blue, bluish, rarely pink. Bluish-green varieties are called aquamarines, emerald green - emeralds. Hardness 7.5 - 8, density 2.6 - 2.8. Most often found in pegmatites and sometimes granites (greisens). They are used in jewelry, instrument making, for the production of beryllium, in rocket and aircraft construction.
Chain silicates
Chain silicates are called pyroxenes and constitute an important group of rock-forming minerals. Their tetrahedrons are connected in chains.
Augite(Ca, Na (Mg, Fe, Al) 2 O 6). The name comes from the Greek word "awe" - shine. Found in short-columnar crystals and irregular grains. The color is black, greenish and brownish black. The line is gray or grayish green. Glass luster, average cleavage. Hardness 6.5, density 3.3 - 3.6. It is the main rock-forming mineral for basic and ultrabasic igneous rocks. When weathered, it decomposes, forming talc, kaolin, limonite.
Band silicates
Band silicates are called amphiboles. Their composition and structure are more complex than those of pyroxenes. In tape silicates, tetrahedrons are connected in double chains. Together with pyroxenes, they make up about 15% of the mass of the earth's crust.
Hornblende((Ca, Na) 2 (Mg, Fe, Al, Mn, Ti) 5 2 (OH, F) 2). crystallizes in long-prismatic columnar crystals, sometimes in aggregates of fibrous or acicular structure. The color is green in various shades, from brownish green to black. The line is white with a greenish tint. Glass luster, perfect cleavage. The fracture is splinter. Hardness 5.5 - 6, density 3.1 - 3.5. Occurs in igneous metamorphic (shale, gneisses, amphibolite) rocks. When weathered, it decomposes, forming limonite, opal, carbonates.
Actinolite(Ca 2 (Mg, Fe) 5 2 2). Found in long prismatic needle crystals. Acicular-radiant aggregates are characteristic. The color is bottle green in various shades, the cleavage is perfect. Hardness 5.5 - 6, density 3.1 - 3.3. Often formed during the metamorphism of limestone, dolomite and basic igneous rocks. Is an part of many shale. Sometimes forms fibrous masses (amphibole asbestos) and forms ornamental stone jade. It is used as an ornamental and facing stone.
Sheet silicates
They are characterized by a very perfect cleavage in one direction, due to which they split into the thinnest elastic leaves. Crystallized in a monoclinic system, most often in the form of tablets, leaves and prisms. Tetrahedrons are connected by a continuous layer in one plane. The formula includes (OH), so they were previously referred to as hydrous silicates. In addition to silicon and oxygen, they include K, Na, Al and Ca - elements that connect the layers to each other. Depending on the chemical composition, they are divided into talc-serpentine, micas, hydromicas and clay minerals.
Talc(Mg 3, 2, wen). The name comes from the Arabic word "talg" - wen. A rock made of talc is called a potting stone. It crystallizes in a monoclinal system in the form of dense masses, leafy aggregates with a very perfect cleavage in one direction. The color is light green to white, sometimes yellowish. Soft, greasy to the touch. Hardness 1, density 2.6. The origin is metamorphic; when heated, the hardness increases to 6. It often forms talc shale. It is formed in the upper horizons of the earth's crust as a result of the action of water and carbon dioxide on rocks rich in magnesium (peridotites, pyroxenites, amphibolites). It is used in paper, rubber, perfumery, leather, pharmaceutical and porcelain industries, as well as for the manufacture of refractory dishes and bricks.
Serpentine(Mg 6, coil). "Serpintaria" from Latin is translated as serpentine (similar to the color of snake skin). occurs in cryptocrystalline aggregates. The color is yellow-green, dark green, to brown-black with yellow spots. Shine is oily waxy. hardness 2.5 - 4. Thin-fiber serpentine with a silky sheen is called asbestos (mountain flax). "Asbestos" in Greek is non-combustible. Formed from olivine as a result of the action of hydrothermal solutions on ultrabasic and carbonate rocks (metamorphic process of serpentinization). Unstable, decomposes into carbonates and opal.
It is used as a facing, ornamental stone, and asbestos fiber - for the manufacture of fire-resistant fabrics, sometimes as a magnesia fertilizer.
Muscovite(KAl 2 2, potassium mica). The name comes from the old Italian name Muscovy (Muscovy). From Muscovy in the XVI-XVII centuries. exported sheets of muscovite called "Moscow glass". Usually forms tabular or lamellar crystals of hexagonal or rhombic cross-section. Colorless, but often with a yellowish, grayish, greenish and rarely with a reddish tinge. The luster is glassy, pearlescent and silvery on the cleavage planes. Hardness 2 - 3, density 2.76 - 3.10. The origin is endogenous and metamorphic. It is found as a rock-forming mineral in acidic igneous rocks and crystalline schists (micaceous sands).
It is appreciated for its high electrical insulating qualities. It is used in capacitors, rheostats, telephones, magneto, electric lamps, generators, transformers, etc. Refractoriness properties make it possible to use muscovite for the windows of smelting furnaces, eyes in forges, as well as for the manufacture of roofing material, artistic wallpaper, paper, paints, lubricants.
In addition to muscovite, biotite (black mica), flagopite (brown, brown mica), hydromica (formations between micas and clays) and glauconite are found.
Kaolinite(Al 4 8, porcelain ground). The name comes from Mount Kau-Ling in China, where this mineral was mined for the first time. It is overlain by loose earthy masses, is the main constituent of clays, and is also a part of marls and shales. The color is white with a yellowish or grayish tint. The line is white, the fracture is earthy, the cleavage is very perfect in one direction. Matte gloss, hardness 1. Greasy to the touch, stains hands. Formed by the weathering of feldspars, micas and other aluminosilicates, it occurs in layers up to several tens of meters thick. It is used in construction, electrical insulation, ceramic, paper industry, in the production of linoleum, paints.
Montmorillonite((Al 2 Mg) 3 3 × nH 2 O). The name comes from its location in Montmorillon (France). Occurs in solid earthy masses, widespread in clayey sedimentary rocks. The color is white, pink, gray, depending on the impurities. Bold to the touch, very perfect cleavage. Hardness 1 - 2. Formed in the process of chemical weathering of basic igneous rocks (gabbro, basalts). As well as ash and tuff. Good adsorbent. Used in oil, textile and other industries.
Frame silicates
Framework silicates are aluminosilicates, since aluminum is included in the radical. Tetrahedrons in framework silicates have continuous adhesion. Frame silicates occupy about 50% of the mass of the earth's crust. They are characterized by high hardness (6 - 6.5), perfect cleavage in 2 directions and glass luster. Frame silicates are divided into two groups - feldspars and feldspatids. Feldspars, in turn, are divided into potassium feldspars(orthoclase and microcline) and sodium-calcium(plagioclases).
Orthoclase(K, stabbing). Translated from Greek orthos - straight; klasis - splitting Crystallizes in monoclinic system. Found in prismatic crystals. The color is yellowish, pink, white, brownish and meat-red; line is white. Cleavage is perfect in two directions, intersecting at right angles. Hardness 6, density 2.56. It is part of acidic and medium igneous rocks. When weathered, it decomposes to clay.
Melting temperature - 145 ° С. It is used in the porcelain and earthenware industries, as well as in the production of glass.
Microcline. In terms of the formula and physical properties, it is indistinguishable from orthoclase. Translated from the Greek microcline - "deflected", because the angle between the cleavage planes deviates from the straight line by 20 ". It crystallizes in the triclinic system. In addition to potassium, it usually contains a certain amount of sodium. It can be distinguished from orthoclase only under a microscope. It is used like orthoclase. , with the exception of amazonite (green or greenish-blue), which is used for decorative purposes.
Plagioclase(sodium-calcium spars) represent a binary series of isomorphic mixtures, in which the extreme members are purely sodium plagioclase - albite and purely calcium - anorthite. The rest of the series are numbered based on the percentage of anorthite. In this case, Na and Si are replaced by Ca and Al and vice versa. The name comes from the Greek word "plagioclase" - skew-splitting, since the cleavage planes differ from the right angle by 3.5 - 4 °.
Albit - Na content of anorthite 0 to 10
Oligoclase 10 - 30
Andesine 30 - 50
Labrador 50 - 70
Bitovnit 70 - 90
Anorthite - Ca 90 - 100
So a Labrador, for example, has no formula. It contains from 50 to 70% anorthite and, accordingly, 50-30% albite. Its number can be 50, 51, 52 ... 70. The content of silicon oxide decreases from albite to anorthite; therefore, albite and oligoclase are called acidic, andesine - medium, and labradorite, bitovnite, anorthite - basic.
All plagioclases crystallize in the triclinic system. Well-formed crystals are relatively rare and have a tabular or tabular-prismatic appearance. They are often found in the form of continuous fine-crystalline aggregates. By external signs, you can determine albite, aligoclase and labrador, and the rest with the help chemical analysis and a microscope.
The color of plagioclases is white, sometimes grayish with a greenish, bluish and less often reddish tinge, the cleavage is perfect. Glass luster. Hardness 6 - 6.5; the density increases from 2.61 (albite) to 2.76 (anorthite). Found in igneous rocks from acidic to basic.
Albite(Na). The name comes from the Latin word "albus" which means white. Hardness 6, glass luster, white color. The cleavage is perfect, the fracture is uneven. It is used as a facing and ornamental stone. When weathered, it transforms into kaolinite.
Labrador. Named for the Labrador Peninsula in North America, where Labradorites (breeds composed of Labradorites) are found. The color is usually dark gray, the luster is glassy, the line is white. Cleavage is perfect. It is well polished, has iridescence - it casts on the cleavage planes in green, blue, violet tones. It is used in the jewelry industry and as a facing and ornamental stone. Weathered to clay minerals.
Feldspatids. They have a skeleton structure. By chemical composition are close to feldspars, but contain less silicic acid.
Nepheline(Na is an oil stone). From the Greek word "nepheli" - cloud. It crystallizes in the hexagonal system, forming prismatic short-columnar crystals, but more often occurs in the form of continuous coarse-grained masses. The color is yellowish-gray, greenish, brownish-red. The gloss is greasy. Cleavage is absent. Hardness 5.5. Found in nepheline syenites and alkaline pegmatites. It is a raw material for the ceramic and glass industry, as well as for the production of aluminum.
Leucite(Ka). "Leikos" in Greek is light. Forms characteristic polyhedral crystals (tetragon-trioctahedrons), similar to garnet crystals. The color is white with a grayish and yellowish tinge or ash gray. The luster is glassy, fractured, cleavage is absent. Hardness 5 - 6, density 2.5. It is found in effusive rocks, often in large quantities. Serves as a raw material for the production of aluminum and potash fertilizers.
Zeolites. Lightly colored, often white minerals - sodium and calcium aluminosilicates. They contain a large amount of water, which is easily released when heated without destroying the crystal lattice of the mineral. Compared to anhydrous aluminosilicates, zeolites are characterized by lower hardness and lower specific gravity. More easily decomposed. They are formed at low temperatures and are found together with calcite, chalcedony. They often fill voids in bubble lavas and are of great importance in soil processes.
Lab 5
Rocks
Rocks are geological independent parts of the earth's crust of more or less constant chemical and mineralogical composition, differing in a certain structure, physical properties and conditions of formation.
Rocks can be monomineral and polymineral. Monomineral rocks are composed of one mineral (gypsum, labradorite). Polymineral rocks are composed of several minerals. Granite, for example, is composed of quartz, feldspars, mica, hornblende, and other minerals.
By origin, all rocks are usually divided into three groups: igneous, sedimentary and metamorphic. Igneous and metamorphic rocks make up about 95% of the mass of the earth's crust, and sedimentary rocks only 5%, but their role is very important. They cover about 75% of the entire earth's surface, soils are formed on them, they are the bases for objects under construction.
Igneous rocks
Igneous rocks are formed as a result of the cooling of fiery liquid rock melts - magma. According to the conditions of formation, igneous rocks are subdivided into intrusive, which have solidified in the bowels of the earth, and effusive, solidified on the earth's surface. Deep rocks are subdivided into deep, or abyssal (depth more than 5 km), and semi-deep, or hypabyssal (from 5 km and closer to the earth's surface) and are transitional from intrusive to effusive rocks.
The conditions for the formation of intrusive and effusive rocks differ significantly from each other, which affects the structure of the rock, which is characterized by structure and texture. Under structure understand the features internal structure rock, depending on the degree of crystallization of the minerals composing it, the size of the grains and their shape.
According to the degree of crystallization, structures are distinguished: full-crystalline, incomplete-crystalline, and glassy.
1. Granular(full-crystalline) is subdivided into coarse, medium and fine grained. The rock consists of grains of minerals tightly pressed against each other. It is typical for deep rocks (granite, syenite, gabbro), etc.
2. Non-crystalline(pyrocrystalline) - the rock of grains does not form (volcanic tuff).
3. Incomplete crystalline... In these rocks, more or less small crystals (microliths) stand out against the background of the glassy mass. It is characteristic of erupted and some semi-deep rocks (trachytes, porphyries, andesites), etc.
4. Cryptocrystalline... The grains are visible only under a microscope (basalt, diabase).
According to the relative size of crystalline grains, uniformly-grained, uneven-grained and porphyry structures are distinguished.
5. Porphyry... Crystals of individual minerals are sharply distinguished by their size against the background of a fine-grained or glassy mass. The inclusions in size exceed the size of the grains of the bulk of the rock dozens of times (porphyrite, trachyte). Sometimes isolated porphyry structure, when the inclusions are only two to three times the size of the main grains.
6. Diabase(needle). This structure is characterized by the presence of elongated crystals. Basically, such a structure is inherent in diabase, but there are diabases with a porphyry structure.
7. Glassy... The peculiarity of the glassy structure is that the poured lava on the surface solidifies, without having time to crystallize. Obsidian and pumice have such a structure with a characteristic glassy luster and a concave fracture.
A number of structures are also distinguished according to the shape of mineral grains: aplite, gabbro, granite, etc.
Under the texture understand the peculiarity of the external structure of the rock, characterized by the arrangement of mineral grains, their orientation and color. According to the location of grains in the rock, a massive and spotty texture is distinguished, and for erupted rocks - a fluid one.
1. Massive(monolithic). It is characterized by a uniform distribution of minerals in the rock mass - all areas of the rock are the same (obsidian, diabase, basalt, granite).
2. Spotted... It is characterized by an uneven distribution of light and dark minerals in the volume of the rock (porphyrites).
3. Fluidal... Typical for erupted rocks with a glassy structure, associated with the flow of lava (flow traces).
4. Porous... It is also typical for erupted rocks and is caused by the release of gases from solidified lava (volcanic tuff, pumice).
5. Slate... Typical for metamorphic rocks. The grains of such textures are flattened and parallel to each other (shales).
The classification of igneous rocks, in addition to their origin, is based on their chemical characteristics or mineralogical composition. Until now, the chemical classification of Levinson - Lessing is used, according to which all igneous rocks are divided, depending on the SiO2 content in magma, into four groups: acidic (65 - 75%), medium (52 - 65%), basic (40 - 52 %) and ultrabasic (less than 40%). Igneous rocks are not equally distributed in the earth's crust. So granites and liparites account for 47%, andesites - 24%, basalts - 21%, and all other igneous rocks - only 8% (Table 1).
Table 1 - Classification of igneous rocks
| Group | Intrusive (deep) | Effusive (outpouring) | Minerals | |
| The main | Secondary | |||
| 1. Ultra acidic | Pegmatite (in the form of veins) | - | Quartz, feldspar | Mica, topaz, wolframite |
| 2. Sour | Granite Pegmatite | Liparite Obsidian Pumice | Quartz, potassium feldspar, acidic plagioclase, biotite, muscovite, hornblende, pyroxenes | Apatite, zircon, magnetite, tourmaline |
| 3. Average | Diorite | Andesite | Medium plagioclases, hornblende, biotite, pyroxenes | Quartz, potassium feldspar, apatite, titanite, magnetite |
| Syenite | Trachyte | Potassium feldspar, hornblende, acidic plagioclases, biotite, pyroxenes | Quartz, titanite, zircon | |
| 4. Basic | Gabbro Labradorite | Basalt Diabase | Major plagioclases, pyroxenes, olivine, hornblende, biotite | Orthoclase, quartz, apatite, magnetite, titanite |
| 5. Ultrabasic | Dunite Peridotite Pyroxenite | - | Olivine, pyroxenes, hornblende | Magnetite, ilmenite, chromite, pyrrhotite |
Acidic rocks