Blue copper sulfate crystals turn white when heated

Complexity:

Danger:

Do this experiment at home

Reagents

Safety

• Before starting the experiment, put on protective gloves and goggles.
• Conduct the experiment on a tray.
• When conducting the experiment, keep a container of water nearby.
• Place the burner on a cork stand. Do not touch the burner immediately after completing the experiment - wait until it cools down.

General safety rules

• Do not allow chemicals to come into contact with your eyes or mouth.
• Keep people away from the experiment site without protective glasses, as well as small children and animals.
• Keep the experimental kit out of the reach of children under 12 years of age.
• Wash or clean all equipment and fixtures after use.
• Ensure that all reagent containers are tightly closed and stored properly after use.
• Make sure all disposable containers are disposed of correctly.
• Use only the equipment and reagents provided in the kit or recommended by current instructions.
• If you have used a food container or glassware for experiments, throw it away immediately. They are no longer suitable for storing food.

First aid information

• If reagents come into contact with your eyes, rinse thoroughly with water, keeping the eye open if necessary. Contact your doctor immediately.
• If swallowed, rinse mouth with water and drink some clean water. Do not induce vomiting. Contact your doctor immediately.
• If reagents are inhaled, remove the victim to fresh air.
• In case of skin contact or burns, flush the affected area with plenty of water for 10 minutes or longer.
• If in doubt, consult a doctor immediately. Take the chemical reagent and its container with you.
• In case of injury, always seek medical attention.

• Improper use of chemicals can cause injury and damage to health. Carry out only the experiments specified in the instructions.
• This set of experiences is intended for children 12 years and older only.
• Children's abilities vary significantly even within age groups. Therefore, parents conducting experiments with their children should use their own discretion to decide which experiments are appropriate and safe for their children.
• Parents should discuss safety rules with their child or children before experimenting. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
• Before starting experiments, clear the experiment site of objects that may interfere with you. Avoid storing food near the test site. The testing area should be well ventilated and close to a tap or other water source. To conduct experiments, you will need a stable table.
• Substances in disposable packaging must be used completely or disposed of after one experiment, i.e. after opening the package.

FAQ

Blue crystals do not turn white. What to do?

10 - 15 minutes have passed, but the crystals of copper sulfate CuSO 4 do not turn white? There seems to be something wrong with the mold heating. Check if the candle is burning. Don’t forget that the mold should be in the center of the flame divider, and the candle in the center of the burner.

Don't get dirty!

Be careful: the candle flame smokes the bottom of the mold quite heavily. It quickly turns black and gets dirty easily.

Do not fill with water!

Do not fill the aluminum mold with copper sulfate with water! This can lead to violent processes: aluminum will be reduced, releasing hydrogen gas. You can find out more about this reaction in the scientific description of the experiment (section “What happened”).

Other experiments

Step-by-step instruction

1. Place three candles in the dry fuel burner and light them. Cover the burner with a flame divider and foil on top.
2. Place an aluminum pan on the foil. Pour one large spoon of copper sulfate crystal hydrate CuSO 4 5H 2 O into it.
3. Watch the color of the crystals change: after 5 minutes the blue crystals will turn blue, and after another 10 they will turn white.

Expected Result

When heated, the water contained in copper sulfate hydrate leaves the crystals and evaporates. The result is white anhydrous copper sulfate.

Disposal

Dispose of experiment solid waste with household waste.

What happened

Why does copper sulfate change color?

Any change in color tells us that the structure of the substance has changed, because it is the substance that is responsible for the very presence of color. From the formula of the original copper sulfate CuSO 4 5H 2 O, it is clear that, in addition to the CuSO 4 sulfate itself, this blue crystalline substance also contains water. Such solids, which contain water molecules, are also called hydrates*.

Water is specially associated with copper sulfate. When we heat this hydrate, water is removed from it, much like a kettle of boiling water. In this case, the bonds between water molecules and copper sulfate are destroyed. This is manifested in a change in color.

To learn more

Let's start with the fact that water molecules are polar, that is, inhomogeneous in terms of charge distribution. What does it mean? The fact is that on one side of the molecule there is a slight excess of positive charge, and on the other - negative. These charges add up to zero - because molecules, as a rule, are not charged. But this does not prevent some of their parts from carrying positive and negative charges.

Compared to hydrogen, oxygen atoms are better at attracting negatively charged electrons. Therefore, on its side, a negative charge is concentrated in the water molecule, and on the other side, a positive charge. This uneven distribution of charges makes its molecules dipoles(from the Greek “dis” - two, “polos” - pole). This “two-facedness” of water allows it to easily dissolve compounds such as NaCl or CuSO 4, because they consist of ions (positively or negatively charged particles). Water molecules can interact with them by turning their negatively charged side (that is, oxygen atoms) towards positively charged ions, and their positively charged side (that is, hydrogen atoms) towards negatively charged ions. And all the particles feel very comfortable with each other. This is why compounds that consist of ions usually dissolve well in water.

It is interesting that during the crystallization of many compounds from aqueous solutions, this interaction is partially retained in the crystal, resulting in the formation of a hydrate. Copper ions, as we see from all the experiments in this set, greatly change their color depending on what particles they are surrounded by.

Both the copper sulfate solution and the CuSO 4 *5H 2 O hydrate have approximately the same deep blue color, which may tell us that the copper ions in both cases are in the same or at least similar environment.

Indeed, in solution, copper ions are surrounded by six water molecules, while in hydrate, Cu 2+ ions are surrounded by four water molecules and two sulfate ions. Another water molecule (after all, we are talking about a pentahydrate) remains associated with sulfate ions and other water molecules, which is largely reminiscent of its behavior in a saturated (that is, the most concentrated) solution of copper sulfate.

When we heat a hydrate, the water molecules are faced with a choice. On the one hand, there are wonderful copper ions - quite pleasant and attractive neighbors. And sulfate ions are also a very decent company. On the other hand, what water molecule does not dream of free flight and exploration of unknown distances? When the temperature rises, the situation in the hydrate becomes tense, and the company no longer seems as decent as the water molecules would like. And they have more energy. Therefore, at the earliest opportunity, they leave copper sulfate, which has indeed turned into a living hell.

When all the water from the hydrate evaporates, only sulfate ions remain surrounded by copper ions. This causes the color of the substance to change from blue to white.

Is it possible to return the blue color?

Yes, you can. There is quite a lot of water in the vapor state in the air around us. Yes, and we ourselves exhale water vapor - remember how glass fogs up if you breathe on it.

If the copper sulfate temperature returns to room temperature, water can “settle” on it in much the same way as on glass. At the same time, it will again bind in a special way to copper sulfate and gradually return its blue color.

You can also speed up this process. If you place dried copper sulfate along with a glass of water in one closed container, the water will “jump” to the copper sulfate from the glass, passing through the air as steam. It should be warned, however, that for this experiment it is necessary to transfer the copper sulfate from the aluminum container to the glass one, since the wet copper sulfate will actively interact with the aluminum metal:

3CuSO 4 + 2Al → Al 2 (SO 4) 3 + 3Cu

This reaction in itself will not spoil the picture much. However, it will destroy the protective Al 2 O 3 shell around the aluminum. The latter, in turn, reacts violently with water:

Al + 6H 2 O → Al(OH) 3 +3H 2

Why might some of the sulfate turn black?

If you overdo it with heating, we can detect another color transition: white copper sulfate darkens.

This is not surprising: we see the beginning of thermal decomposition (breakdown into parts under the influence of temperature) of copper sulfate:

2CuSO 4 → 2CuO + 2SO 2 + O 2

In this case, black copper oxide CuO is formed.

To learn more

There is a general rule in chemistry: if the atoms that make up a solid substance can form gaseous products, then when heated it will almost certainly decompose with the formation of these same gases.

For example, the sulfur S and oxygen atoms O contained in copper sulfate can form gaseous sulfur oxide SO 2 and molecular oxygen O 2. Now let’s return to the reaction equation for the thermal decomposition of copper sulfate: 2CuSO 4 → 2CuO + 2SO 2 + O 2

As we can see, it is these gases that are released if copper sulfate is heated thoroughly.

Development of the experiment

How to make copper sulfate turn blue again?

It's actually very easy! There are several options.

First, you can simply pour the dehydrated sulfate into a plastic container (like a Petri dish) and leave it out in the open. The sulfate will act as a desiccant and gradually absorb water from the air. After a while it will turn light blue, and then blue. This means that the composition of its crystals is again CuSO 4 * 5H 2 O. This option is the simplest, but it has one drawback: developing the experiment in this way can take several days.

Secondly, you can speed up the process. It is most convenient to use the Petri dish again, but with both parts of it. Pour all (or part) of the white copper sulfate into a cup. Nearby, at the bottom of the cup, add a couple of drops of water. Make sure that the water does not get on the sulfate (otherwise it would be too easy!). Now cover the Petri dish with its lid. After a few hours the sulfate will turn blue again. This time the transformation takes less time, since we have actually created a “chamber” with excess water vapor inside.

The third way is to add water drop by drop directly into the white copper sulfate. Again, it is most convenient to use a Petri dish, although you can also use a regular disposable plastic cup from the Starter Kit. Don't add too much water - your goal is not to dissolve the copper sulfate, but to saturate it with moisture!

Finally, the fourth option is to dissolve the resulting anhydrous copper sulfate. Do this in a disposable plastic cup. You will receive a blue solution. By the way, if you let the water from this solution evaporate slowly (at room temperature), blue CuSO 4 * 5H 2 O crystals will form in the glass.

So, there are many ways to return the blue color to copper sulfate crystals. The most important thing is that this reaction reversible, which means you can repeat the experiment again and again, changing the methods for obtaining blue copper sulfate crystalline hydrate.

It is important to remember that the development of the experiment should not be carried out in an aluminum mold. To find out why, read the answer to the question “What happened? “Is it possible to return the blue color?”

What are crystalline hydrates and why are they formed?

Many salts, that is, compounds consisting of positively charged metal ions and a variety of negatively charged ions, can form special adducts(from the English to add – add) – hydrates or crystalline hydrates. Essentially, an adduct is parts put together. Many compounds are called this, either for simplicity and convenience, or to indicate that they consist of a pair of component parts.

In this case, the adducts in question differ from ordinary salts in that they contain water. This water is also called crystallization. And indeed, it is part of the crystal! This usually happens when salts crystallize from aqueous solutions. But why does water remain in the crystal?

There are two main reasons for this. As is known, compounds that are highly soluble in water (and these are many salts) dissociate in it, that is, they break up into positively and negatively charged ions. So, the first reason is that these ions are in a special environment consisting of water molecules. When the solution is concentrated (in our case, when the water gradually evaporates), these ions come together and form a crystal. At the same time, they often preserve their surroundings to some extent, actually taking water molecules with them into the crystal.

However, not all salts tend to form hydrates. For example, sodium chloride NaCl always crystallizes without water in its composition, although in solution each ion is surrounded by five to six H 2 O molecules. Therefore, it is necessary to mention the second reason. Like people, everyone is looking for a more comfortable place. It turns out that in some cases this “comfort” is much better provided precisely by water molecules, and not by “antipode” ions (as is the case with Na + and Cl -). That is, the bonds of ions with water molecules turn out to be stronger. This property is more characteristic of positively charged ions, and in most crystalline hydrates water is found precisely in their environment. This is made possible by electrostatic attraction (the attraction between “+” and “–”) between the ions and the water molecule, in which there is a slight negative charge on the oxygen atom and a positive charge near the hydrogen atoms.

All crystalline hydrates decompose when heated. At temperatures above 100 o C, water exists in the form of steam. It is under such conditions that water molecules tend to leave the crystalline hydrate.

That is, the structure of this substance also includes water molecules. It has the same basic properties that are characteristic of ordinary cuprum sulfate. It should be said that this is a salt, so it is characterized by chemical behavior that is characteristic of many other substances in this group.

Physical properties

Copper sulfate is a blue crystalline solid. It is soluble in water. For one molecule of cuprum sulfate in the structure of the substance there are five molecules of water. Anhydrous, it does not have any color. In nature, it can be found in the form of certain minerals, such as chalcanthite. This stone is little known and rarely used.

Chemical properties of copper sulfate (copper sulfate)

Like any other sulfate, copper sulfate can decompose when exposed to high temperatures. This type of reaction produces cuprum oxide, sulfur dioxide and oxygen. Also, copper sulfate, like other salts, can be a participant in the substitution reaction. In this kind of interaction, the more active metal, which is to the left of cuprum in the electrochemical series of activity, displaces the copper atom from the compound and takes its place. For example, by adding sodium to the substance in question, you can get sodium sulfate and copper, which will precipitate. In addition, this substance is capable of reacting with basic and acidic hydroxides, as well as other salts. An example is the reaction of cuprum sulfate with calcium hydroxide, a base. As a result of this interaction, copper hydroxide and calcium sulfate are released. As an example of the reaction of this salt with an acid, we can take its interaction with phosphoric acid, which results in the formation of copper phosphate and sulfate acid. When copper sulfate is mixed with a solution of another salt, an exchange reaction occurs. That is, if you add to it, for example, barium chloride, you can get copper chloride and barium sulfate, which precipitate (if one of the products is not a sediment, gas or water, the reaction cannot take place).

Obtaining this substance

Copper sulfate can be obtained using two main methods. The first is the reaction of copper hydroxide with concentrated sulfate acid. In this case, a significant amount of water is also released, part of which is used for hydration. The second method of obtaining this substance is the interaction of concentrated sulfuric acid directly with copper. This kind of reaction can only take place under specific conditions in the form of elevated temperature. It is also possible to carry out a reaction between copper oxide and sulfate acid, as a result of which the desired substance and water are also formed. In addition, copper sulfate is obtained by roasting copper sulfites.

Use of copper sulfate

This substance has found its main application in the horticultural field - it is used to protect plants from diseases and pests thanks to its antiseptic and disinfectants. This substance is also widely used in agriculture, since it can be used to increase the frost resistance and immunity of plants to fungi. In addition, copper sulfate is used in metallurgy, as well as in construction. Wood is impregnated with it to give it fire-resistant properties. In the food industry it is often used as a preservative. In addition to all of the above, copper sulfate is used to make paints and to carry out high-quality reactions to zinc, manganese and magnesium cations.

Copper sulfate crystals

An interesting and exciting activity for children is growing crystals from a variety of substances. The raw materials for such an entertaining experiment can be many different compounds, including kitchen salt, as well as copper sulfate. The properties of this substance make it possible to grow a large crystal from its powder, purchased at any gardening store. You won't need to put in too much effort to do this. To grow a crystal of copper sulfate, you need to take any container. Pour water into it and add the powder itself, while heating the liquid to promote faster dissolution of the substance in it. Copper sulfate should be added as long as it can be dissolved in water. This way we get a very saturated solution. Then you can leave it like that, simply covering it with something, or you can fasten a thread on the inside of the lid with a bead or button suspended on it so that it hangs evenly - this way the crystals will grow on the thread, and not on the bottom of the container. You need to make sure that it is not moved from place to place, otherwise nothing will work. Every day or every few days, you need to add a little copper sulfate to the solution to maintain high saturation so that the crystals do not begin to dissolve again in the water. After about two weeks of such manipulations, if everything is done correctly, you can get a fairly large crystal.

Copper sulfate. Qualitative reactions carried out with its help

Using this substance, you can determine the presence of zinc cations. If you add copper sulfate to the solution and a cloudy precipitate forms, it means it contains zinc compounds. Also, using the substance in question, you can determine the presence of magnesium cations. In this case, a precipitate will also form in the solution.

How to determine that there is copper sulfate in a solution?

The most common qualitative reaction that can be carried out at home is the interaction of the solution with iron. You can take any iron product. If, after dipping it into the solution for a while, you see a reddish coating on it, it means copper sulfate is present. This plaque is copper that has settled on an iron product. Ferrous sulfate, which is also released as a result of this substitution reaction, goes into the test solution. Another, less accessible option for determining the presence of a given substance in a solution is a reaction with any soluble barium salt. In this case, barium sulfate will precipitate. You can also carry out a test using any aluminum product according to the same principle as the first reaction described. In this case, a reddish coating should also form, which indicates the replacement of cuprum atoms by aluminum atoms and the formation of aluminum sulfate and pure copper.

Conclusion

To briefly summarize everything written above, we can say that copper sulfate is a very widespread and well-known substance that is used in many areas of human life. It can find its application both in various industries and at home: for entertainment purposes or for caring for plants. This substance is also popular among those who breed fish - it protects the aquarium from contamination by microalgae. Cuprum sulfate is easy to obtain in the laboratory. It has a low cost, which is why it has become so widespread and is used for a wide variety of purposes.

Copper belongs to the group of seven metals that have been known to man since ancient times. Today, not only copper, but also its compounds are widely used in various industries, agriculture, everyday life and medicine.

The most important copper salt is copper sulfate. The formula of this substance is CuSO4. It is a strong electrolyte and consists of small white crystals, highly soluble in water, without taste or odor. The substance is non-flammable and fireproof; when used, the possibility of spontaneous combustion is completely excluded. Copper sulfate, when exposed to even the smallest amount of moisture from the air, acquires a characteristic blue color with bright blue. In this case, copper sulfate is converted into blue pentahydrate CuSO4 · 5H2O, known as copper sulfate.

In industry, copper sulfate can be obtained in several ways. One of them, the most common, is dissolving copper waste in diluted copper sulfate. In the laboratory, copper sulfate is obtained using a neutralization reaction with sulfuric acid. The process formula is as follows: Cu(OH)2 + H2SO4 → CuSO4 + H2O.

The color changing property of copper sulfate is used to detect the presence of moisture in organic liquids. It is used to dehydrate ethanol and other substances in laboratory conditions.

Copper sulfate or copper sulfate is widely used in agriculture. Its use, first of all, consists of using a weak solution to spray plants and treat cereals before sowing in order to destroy harmful fungal spores. Based on copper sulfate, the well-known Bordeaux mixture and milk of lime are produced, sold through retail outlets and intended to treat plants from fungal diseases and destroy grape aphids.

Copper sulfate is often used in construction. Its use in this area is to neutralize leaks and eliminate rust stains. The substance is also used to remove salts from brick, concrete or plastered surfaces. In addition, it is used to treat wood as an antiseptic to avoid rotting processes.

In official medicine, copper sulfate is a medicine. It is prescribed by doctors for external use as eye drops, solutions for rinsing and douching, and also for the treatment of burns caused by phosphorus. As an internal remedy, it is used to irritate the stomach to induce vomiting if necessary.

In addition, mineral paints are made from copper sulfate; it is used in spinning solutions for making

In the food industry, copper sulfate is registered as food additive E519, used as a color fixative and preservative.

When copper sulfate is sold in retail stores, it is labeled as a highly hazardous substance. If it enters the human digestive system in an amount of 8 to 30 grams, it can be fatal. Therefore, when using copper sulfate in everyday life, you should be very careful. If the substance gets on your skin or eyes, rinse the area thoroughly with cool running water. If it enters the stomach, it is necessary to do a weak rinse, drink a saline laxative and a diuretic.

When working with copper sulfate at home, use rubber gloves and other protective equipment, including a respirator. It is prohibited to use food containers for preparing solutions. After finishing work, be sure to wash your hands and face, and rinse your mouth.

Introduction

Many living organisms are capable of causing serious damage to humans, domestic animals, plants, as well as destroying non-metallic and metallic materials and products made from them.

Of the numerous methods of plant protection, the most important is the chemical method - the use of chemical compounds that destroy harmful organisms. The chemical method is also effective for protecting various materials and products made from them from biological destruction. Recently, pesticides have become widely used in the fight against various pests.

Pesticides (lat. pestis - infection and lat. caedo - kill) are chemicals used to combat harmful organisms.

Pesticides include the following groups of such substances: herbicides that destroy weeds, insecticides that destroy insect pests, fungicides that destroy pathogenic fungi, zoocides that destroy harmful warm-blooded animals, etc.

Most pesticides are poisons that poison target organisms; they also include sterilants (substances that cause infertility) and growth inhibitors.

2.1 Copper sulfate and its properties

Copper sulfate CuSO 4 crystallizes from aqueous solutions of copper sulfate and represents bright blue crystals of the triclinic system with lattice parameters. Density 2.29 g/cm3.

When heated above 105°C, it melts with the loss of part of the water of crystallization and becomes CuSO 4 . 3H 2 O (blue) and CuSO 4 H 2 O (white). Completely dehydrates at 258°C. When dry NH 3 acts on CuSO 4, CuSO 4 5NH 3 is formed, which exchanges NH 3 for H 2 O in humid air. With alkali metal sulfates, CuSO 4 forms double salts such as Me 2 SO 4 CuSO 4 6H 2 O, colored greenish.

In industry, copper sulfate is obtained by dissolving copper metal in heated dilute H 2 SO 4 while blowing air: Cu + H 2 SO 4 + ½O 2 = CuSO 4 + H 2 O. It is also a by-product of electrolytic refining of copper.

Copper sulfate is the most important commercial copper salt. It is used in the production of mineral paints, wood impregnation, to combat pests and plant diseases in agriculture, for grain dressing, in leather dressing, in medicine, in galvanic cells; serves as a starting product for the production of other copper compounds.

Copper sulfate (copper sulfate) CuSO 4 - colorless crystals 3.64 g/cm3. When heated, they dissociate: CuSO 4 = CuO + SO 2 + ½O 2 with the formation of the main sulfate CuO CuSO 4 as an intermediate product. At 766°C, the dissociation pressure of CuSO 4 reaches 287 mm. rt. column, and CuO CuSO 4 - 84 mm. rt. pillar The solubility of CuSO 4 in grams per 100 g of water is: 14 (0°C); 23.05 (25°C); 73.6 (100°C). In the presence of free H 2 SO 4, solubility decreases. At pH 5.4-6.9, CuSO 4 hydrolyzes to form basic salts. CuSO 4 is very hygroscopic, therefore it is used as a drying agent; adding water, it turns blue, which is sometimes used to detect water in alcohol, ether and others.

When heated, copper sulfate loses water and turns into gray powder. If, after cooling, you drop a few drops of water on it, the powder will again acquire a blue color.

2.2 Iron sulfate and its properties

Ferrous sulfate (2)

Systematic name Iron 2 tetraoxiosulfate.

Physical properties: crystalline state, molar mass 151.932 g/mol, density 1.898 g/cm3

Iron (2) sulfate, iron (2) sulfate-inorganic binary compound, iron salt of sulfuric acid with the formula FeSO 4. Heptahydrate FeSO 4 ∙H 2 O has the trivial name iron sulfate. Crystalline hydrates are hygroscopic transparent crystals of light bluish-green color, FeSO 4 ∙H 2 O monohydrate is colorless (smolnikit). The taste is strongly astringent, ferrous (metallic). In air they gradually erode (lose water of crystallization). Ferrous sulfate (‖) is highly soluble in water. A bluish-green heptahydrate crystallizes from aqueous solutions. The toxicity of iron sulfate is relatively low.

It is used in the textile industry, in agriculture as a fungicide, for the preparation of mineral paints.

Properties.

Ferrous sulfate will be released at temperatures from 1.82˚C to 56.8˚C from aqueous solutions in the form of light green crystals of crystalline hydrate FeSO 4 ∙ 7H 2 O, which is called iron sulfate in technology. Dissolves in 100 g of water: 26.6 g of anhydrous FeSO 4 at 20˚C and 54.4 at 56˚C.

Solutions of iron sulfate (‖) under the influence of atmospheric oxygen gradually oxidize, turning into iron sulfate (׀׀׀):

12FeSO 4 +3O 2 +6H 2 O→ 4 Fe 2 (SO 4)3 + Fe(OH) 3 ↓

When heated above 480˚C, it decomposes:

2FeSO 4 →Fe 2 O 3 + SO 2 +SO 3

Receipt

Iron sulfate can be prepared by treating scrap iron, cuttings of roofing iron, etc. with dilute sulfuric acid. In industry, it is obtained as a by-product during the pickling of iron sheets, wire, descaling, and other diluted H 2 SO 4.

Fe+ H 2 SO 4 → FeSO 4 + H 2

Another method is oxidative roasting of pyrite:

FeS 2 +3 O 2 → FeSO 4 + SO 2

Used in the production of ink, in dyeing (for dyeing wool black), and for preserving wood.

2.3 Bordeaux mixture (copper sulfate + calcium hydroxide)

Chemical formula CuSO 4 3Cu(OH) 2

Bordeaux mixture, Bordeaux mixture (copper sulfate + calcium hydroxide) is a pesticide, protective contact fungicide and bactericide. In increased doses, it has an eradicating effect on dormant forms of plant pathogens. Used for early spring treatment of gardens, vineyards, berry fields by spraying.

Physicochemical characteristics

Bordeaux mixture is the main copper sulfate with an admixture of gypsum. A properly prepared suspension is quite stable, has good adhesion, retention on the surface of plants and high fungicidal activity. This is a blue liquid, which is a suspension of colloidal particles of the active substance - copper metal. A properly prepared drug should have a neutral or slightly alkaline reaction. A strongly alkaline preparation does not adhere well to the surface of plants, while a strongly acidic phytociden. The reaction of the solution is determined by immersing an iron wire or nail in it: in an acidic environment, a coating of copper appears on them, and in this case it is necessary to add milk of lime to the solution. To increase adhesive properties, liquid glass (silicate glue), casein glue, molasses, sugar, skim milk, eggs and synthetic surfactants are sometimes added to Bordeaux mixture.

Bordeaux mixture is prepared from copper sulfate and lime. Let us present the physical and chemical properties of each of these substances.

СuSO 2 – copper (II) sulfate. The substance is white, very hygroscopic, low-melting, and decomposes when heated strongly. Crystalline hydrate CuSO 4 3H 2 O (chalcanthite, copper sulfate) has the structure [Cu(H 2 O) 4 ]SO 4 H 4 O.

It is highly soluble in water (cation hydrolysis). Reacts with ammonia hydrate, alkalis, active metals, hydrogen sulfide. Enters into complexation and exchange reactions.

Physical characteristics of CuSO 4

Molecular weight 159.6 g/mol;

Melting point ~ 200 °C;

Relative density 3.603g/cm3 (at room temperature).

Ca(OH) 2 – calcium hydroxide, slaked lime. The substance is white and decomposes when heated without melting. It is poorly soluble in water (a dilute alkaline solution is formed). Reacts with acids and exhibits basic properties. Absorbs CO 2 from the air.

Physical characteristics of Ca(OH) 2

Molecular weight 74.09 g/mol;

Relative density 2.08 g/cm3 (at room temperature).

Effect on harmful organisms

The fungicidal effect of Bordeaux mixture is due to the fact that during hydrolysis under the influence of carbon dioxide in the air, secretions of fungi and plants, the main salt of copper sulfate decomposes and releases copper sulfate in small quantities:

CuSO 4 Cu(OH) 2 + H 2 O + 3CO 2 → CuSO 4 + 3CuCO 3 + 4H 2 O

If this process occurs intensively (at high humidity and temperature), then the protective effect of the fungicide will be short-lived, and plant damage may occur.

The last processing period for most crops ends 15 days before harvest, melons - 5 days, tomatoes - 8 days before harvest, subject to careful sprinkling during harvesting.

Bordeaux mixture is one of the universal fungicides with the longest protective effect (up to 30 days). In almost all cases it has a stimulating effect on plants. The effectiveness of the drug depends on the period of its use. The best results are obtained from treatments shortly before infection. According to other literature data, it is more advisable to use the drug in late autumn and at the beginning of bud break. In these cases, it has almost no negative impact on the protected crop (phytotoxicity is lower).

When plants are treated with Bordeaux mixture, the main copper sulfate precipitates in the form of a gelatinous precipitate, which adheres well to the leaves and covers them and the fruits of the plants with a protective layer. In terms of retention on leaves, Bordeaux mixture ranks first among fungicides. Has repellent properties for many insects.

Mechanism of action.

The biological properties of copper-containing preparations are determined by the ability of copper ions to actively react with lipoprotein and enzyme complexes of living cells, causing irreversible changes (coagulation) of protoplasm. Copper ions entering the pathogen cells in sufficiently high concentrations interact with various enzymes that contain carboxyl, imidazole and thiol groups and suppress their activity. In this case, first of all, the processes included in the respiratory cycle are inhibited. They also cause nonspecific denaturation of proteins. Their selectivity towards beneficial organisms depends on the amount of copper ions that enter the cells and accumulate in them. Conidia and fungal spores that germinate on the surface of plants in a drop of water are capable of concentrating copper ions inside their cells, creating a concentration 100 or more times higher than in plant cells or outside.

Bordeaux mixture has repellent properties for many insects.

Resistant species.

Bordeaux mixture is not effective against peronosporosis of shag and tobacco, as well as against powdery mildew.

Insecticidal and acaricidal properties. Bordeaux mixture has repellent properties for many insects.

Suppresses psyllids on potatoes. Shows ovicidal effect.

Application

Bordeaux mixture ranks first among protective fungicides in terms of adhesion and retention on plant surfaces. However, due to the high consumption of copper sulfate, the difficulty of preparation, as well as the possibility of damaging plants, this fungicide is replaced with copper oxychloride and organic preparations.

Registered preparations based on Bordeaux mixture are approved for use in agriculture and private farms against diseases of sugar beet, fodder beet, table beet (cercospora), onion (peronospora), apricot, peach, plum, cherry, sweet cherry (coccomycosis, curl, moniliosis), gooseberry (anthracnose, rust, septoria), etc.

Bordeaux mixture should not be mixed with organophosphate insecticides and other drugs that decompose in an alkaline environment.

Phytotoxicity: On the surface of plants in the presence of drip-liquid moisture, particles of basic copper sulfate are slowly hydrolyzed, and copper ions enter the water in relatively small quantities. At the same time, the danger of plant burns is significantly reduced. Such burns occur only with a significant increase in concentration, poor quality Bordeaux mixture, increased amount of precipitation after treatment, or acidic air pollution. Also, if the drug is prepared incorrectly, growth may be inhibited and a “net” may appear on the leaves and fruits.

The drug causes crushing of cherry fruits with an increase in the content of sugars and dry matter, the formation of a “net” on the fruits and leaves of copper-sensitive apple tree varieties, “burns” the leaves and reduces the survival rate of budding due to drying out the bark of the rootstocks. Heavy rainfall contributes to damage. Phytocidal activity also increases with the age of trees. On the Daibera black cherry variety, with sharp temperature fluctuations and drought, Bordeaux liquid contributed to summer leaf fall and oppression of trees.

Toxicological properties and characteristics

Entomophages and beneficial species. The drug has low toxicity for bees, however, it is better to isolate the bees during the period of crop treatment and for the next 5 hours to one day. Quite toxic to the predatory mite Anistis (when used at a concentration of 0.09%, its number on black currants decreased by 3-4 times). Slightly toxic to Encyrtidae and moderately toxic to Trichogrammatidae. At a concentration of 1% it is low toxic to Encarzia puparia. The period of residual action for adults is no more than a day. Moderately toxic to Creptolemus.

The mixture is not poisonous to other predatory mites, coccinellids, lacewing larvae and adults, predatory gall midges and hymenopterans such as aphenylids, pteromalids, and their neumonids.

Warm-blooded. Bordeaux mixture is low-toxic for warm-blooded animals and humans. According to other literary sources, the drug is moderately toxic for warm-blooded animals: oral LD50 for mice is 43 mg/kg, for rats 520 mg/kg. The concentrated drug irritates the mucous membranes.

Symptoms of poisoning

Eating fruits for the first days after treatment with preparations containing copper sulfate causes nausea and vomiting.

Preparation of the solution

Bordeaux mixture is prepared by mixing a solution of copper sulfate with a suspension of quicklime. The quality of the prepared mixture depends on the ratio of components, the quality of quicklime and the preparation procedure. High quality is ensured when the component ratio is 1:1 or 4:3 and the reaction occurs in an alkaline environment. Preparation involves slowly pouring a solution of copper sulfate in a small stream into a suspension of lime. Constant stirring is required. The resulting dark blue liquid should resemble diluted jelly.

If this process is disrupted, the content of copper hydroxide in the mixture increases, which oxidizes on the surface to insoluble copper oxide, and the number of large (up to 10 microns) particles increases, which reduces the stability and adhesion of the drug. The laboriousness of preparation and the need for equipment for this are the disadvantages of Bordeaux mixture.

To prepare 100 liters of a 1% preparation, take 1 kg of copper sulfate and 0.75 kg of quicklime (if the lime is of poor quality - up to 1 kg). Copper sulfate is dissolved in a small volume of hot water and brought to 90 liters with water. Quicklime is slaked by adding water to it until a creamy mass is formed, and then lime milk is formed, the volume of which is also adjusted with water to 10 liters. Lime milk is poured with constant stirring into the copper sulfate solution. With the indicated recipe, it is also possible to add a solution of copper sulfate to lime milk, but you cannot mix strong solutions of these components, and also pour a strong solution of copper sulfate into a weak solution of lime milk. In these cases, spherical crystals of basic copper sulfate are formed, which are easily washed off from plants by precipitation. A similar phenomenon is observed when the drug ages.

To prepare Bordeaux mixture, do not use containers made of materials susceptible to corrosion.

Bordeaux mixture is prepared immediately before use and only in the required concentration. The prepared solution should not be diluted with water, as in this case it will quickly separate. During long-term storage, aggregation of Bordeaux mixture particles occurs, causing their precipitation and poor retention on plants.

Today, manufacturing companies offer Bordeaux mixture in powder form. It is prepared by complete neutralization of copper sulfate with slaked lime, dried and micronized. Due to the special fineness of the particles, the working composition has maximum adhesion, and the resulting suspension is very stable.

Introduction

In a building supply store you saw a bucket with a name unknown to you: “Mineral paint”. Curiosity takes over and your hand reaches out towards him. We read the composition: “Lime, table salt, etc., etc...” “What kind of copper sulfate is that?” - our eyes caught the name of the unfamiliar substance. I am sure that most people heard about copper sulfate in such a situation Others would just give up on this, but not you. Surely you want to know more about it. Therefore, the topic of today's article will be copper sulfate.

Definition

Due to the variable valency of copper, there are only two sulfates in chemistry - I and II. Now we will talk about the second sulfate. It is an inorganic binary compound and is a copper salt of sulfuric acid. This copper sulfate (formula CuSO 4) is also called copper sulfate.

Properties

It is a non-volatile, colorless, opaque and very hygroscopic, odorless substance. However, the properties of copper sulfate crystal hydrates themselves differ significantly from its characteristics (as a substance). They look like transparent, non-hygroscopic crystals, which have various shades of blue (photo above) and a bitter metallic taste. Copper sulfate is also highly soluble in water. If you crystallize its aqueous solutions, you can get copper sulfate (photo). Hydration of anhydrous copper sulfate is an exothermic reaction in which significant heat is released.

Receipt

In industry, it is obtained contaminated by dissolving copper and copper waste in dilute sulfuric acid, which, in addition, is purged with air.
Copper sulfate can also be obtained in the laboratory in several ways:

• Sulfuric acid + copper (when heated).
• Sulfuric acid + copper hydroxide (neutralization).

Cleaning

To purify copper sulfate obtained by such methods, recrystallization is most often used - it is immersed in boiling distilled water and kept on fire until the solution becomes saturated. Then it is cooled to +5 o C and the resulting precipitate, reminiscent of crystals, is filtered off. However, there are also methods for deeper cleaning, but they require other substances.

Copper sulfate: application

Using anhydrous copper sulfate, ethanol is absolutized and gases are dried; it also serves as a humidity indicator. In construction, an aqueous solution of copper sulfate neutralizes the effects of leaks, eliminates rust stains and removes salt secretions from plastered, brick and concrete surfaces, and also prevents wood rotting. In the agricultural sector, copper sulfate, formed from copper sulfate, serves as an antiseptic, fungicide and copper-sulfur fertilizer. Solutions of this substance (with different concentrations) disinfect plants, trees and soil. Bordeaux mixture, well known to farmers, also partly consists of copper sulfate. It is also one of the ingredients included in mineral paints. They cannot do without it in the production of acetate fibers. Copper sulfate is also known as a food additive E519, used as a color fixative and preservative. Also, a solution of copper sulfate can detect zinc, manganese in aluminum alloys and stainless steel: if they contain the above impurities, then upon contact with this solution, red spots will appear on their surface.

Conclusion

Copper (II) sulfate itself is little known, but everyone has heard about the product of its reaction with water - copper sulfate. And, as you can see, it brings very great benefits.