Chemistry of color qualitative reactions. Abnormal precipitation: "colored" rains and "chocolate" snow. Help All precipitation and their colors
The Pambak River in the Lori region in northern Armenia has acquired a reddish hue, water samples were taken for examination.
April 1999 after the NATO bombing of Yugoslavia and the destruction of petrochemical enterprises, a poisonous "black rain" passed over the town of Pancevo, containing a huge amount of heavy metals and organic compounds harmful to human life. Soil and groundwater were seriously polluted, which turned out to be contaminated with ethylene and chlorine. A huge amount of oil, oil products, ammonia and amino acids got into the Danube.
June-July 2000 in some regions of Dagestan and North Ossetia, in particular, in the city of Vladikavkaz, there were "colored rains". As a result of analyzes of water samples, an increased content of chemical elements was found. They exceeded the maximum allowable concentrations of cobalt (more than four times) and zinc (more than 434 times). Laboratory studies confirmed that the composition of the polluted rain was identical to the chemical composition of the samples taken on the territory of JSC "Electrozinc", which violated the standards for maximum allowable emissions into the atmosphere, approved by the Ministry of Environmental Protection.
In 2000 and 2002"rusty" precipitation fell in the Altai Territory and the Altai Republic. The weather anomaly was caused by strong emissions of combustion products at the Ust-Kamenogorsk metallurgical plant.
July-September 2001"red rains" repeatedly fell out in the Indian state of Kerala. Several hypotheses of the origin of red particles were put forward at once: someone considered them to be red dust carried by the wind from the Arabian Desert, someone recognized them as fungal spores or ocean algae. A version of their extraterrestrial origin was put forward. According to scientists, a total of about 50 tons of this strange substance fell on the ground along with precipitation.
In October 2001 residents of the southwestern regions of Sweden fell under abnormal rain. After the rain, gray-yellow stains remained on the surface of the earth. Swedish experts, and in particular a researcher from the Gothenburg Geoscience Center Lars Fransen, said that strong winds "druck" red sand dust from the Sahara, raised it to a height of up to 5 thousand meters and then poured it along with the rain in Sweden.
Summer 2002 green rain poured over the Indian village of Sangranpur near the city of Kolkata. Local authorities announced that there was no chemical attack. The examination of scientists who arrived at the site determined that the green cloud is nothing more than pollen from flowers and mangoes contained in bee excrement, and does not pose a danger to humans.
In 2003 in Dagestan, precipitation in the form of salt deposits fell. Cars standing in the open air were covered with a layer of salt. According to meteorologists, the reason for this was a cyclone that came from the regions of Turkey and Iran. Fine particles of sand and dust raised by a strong wind from the developed quarries in the territory of Dagestan mixed with water dust raised from the surface of the Caspian Sea. The mixture was concentrated in clouds that moved to the coastal regions of Dagestan, where unusual rain fell.
Winter 2004 orange-colored snow fell in eastern Poland. At the same time, residents of Transcarpathia observed him in the villages of Quiet and Gusinoe. According to one version, sandstorms in Saudi Arabia became the reason for the orange color of the snow: grains of sand, picked up by a strong wind, accumulated in the upper atmosphere and fell along with snow in Transcarpathia.
April 19, 2005 red rain fell in Kantemirovskiy and Kalacheevskiy districts of the Voronezh region. Precipitation left an unusual trace on the roofs of houses, fields, agricultural machinery. In a soil sample, traces of ocher, a natural pigment for paint production, were found. It contained hydroxides of iron and clay. Further investigation revealed that there had been a release at the ocher factory in the village of Zhuravka, which caused the rain clouds to turn red. According to experts, the precipitation did not pose a danger to the health of people and animals.
April 19, 2005 over several regions of the Stavropol Territory, the sky acquired a yellowish tint, and then it began to rain, the drops of which were colorless. After drying, the drops were left on cars and on dark beige clothes, which were not washed off afterwards. The same rain fell on April 22 in Orel. The analyzes carried out showed that the sediments contained alkali, namely, nitrogenous compounds. The precipitation was very concentrated.
April 2005 for several days, orange rains were falling in Ukraine - in the Nikolaev region and in the Crimea. Colored precipitation also covered Donetsk, Dnepropetrovsk, Zaporozhye, Kherson regions these days. Ukrainian weather forecasters said that the orange color of the rain acquired due to a dust hurricane. The wind brought dust particles from North Africa.
February 2006 gray-yellow snow fell on the territory of the village of Sabo, located 80 km south of the city of Okha in the north of Sakhalin. According to eyewitnesses, oily spots of a gray-yellow color and with an unusual strange smell formed on the surface of the water obtained by melting suspicious snow. Experts believe that unusual precipitation could be the consequences of the activity of one of the Far Eastern volcanoes. Possibly, the pollution of the environment by products of the oil and gas industry is to blame. The reason for the yellowing of the snow was not exactly established.
February 24-26, 2006 in some areas of Colorado (USA) it was brown snow, almost like chocolate in color. "Chocolate" snow in Colorado - a consequence of a long drought in neighboring Arizona: there are giant clouds of dust that mixes with snow. Sometimes volcanic eruptions give the same result.
March 2006 creamy-pink snow fell in the north of Primorsky Krai. Experts explained the unusual phenomenon by the fact that the cyclone had previously passed through the territory of Mongolia, where strong dust storms raged at that time, covering large expanses of desert territories. Dust particles were drawn into the vortex of the cyclone and colored the precipitation.
March 13, 2006 in South Korea, including Seoul, yellow snow fell. The snow was yellow because it contained yellow sand brought from the deserts of China. The country's meteorological service has warned that snow containing fine sand can be dangerous for the respiratory system.
November 7, 2006 in Krasnoyarsk, light snow fell with green rain. He walked for about half an hour and, having melted, turned into a thin layer of greenish clay. People exposed to green rain experienced tearing and headaches.
January 31, 2007 in the Omsk region, on an area of \u200b\u200babout 1.5 thousand square kilometers, yellow-orange snow fell with a pungent odor, covered with oily spots. Having passed through the entire Irtysh region, a plume of yellow-orange precipitation touched the Tomsk region along the edge. But the main part of the "acidic" snow fell in the Tarsky, Kolosovsky, Znamensky, Sedelnikovsky and Tyukalinsky districts of the Omsk region. In colored snow, the norm of iron content was exceeded (according to preliminary laboratory data, the concentration of iron in snow was 1.2 mg per cubic centimeter, while the maximum allowable norm was 0.3 mg). According to Rospotrebnadzor, such a concentration of iron is not dangerous for human life and health. Abnormal precipitation was studied by laboratories in Omsk, Tomsk and Novosibirsk. At first it was assumed that the snow contained the poisonous substance heptyl, which is a component of rocket fuel. The second version of the appearance of yellow precipitation was the emissions of the metallurgical enterprises of the Urals. However, Tomsk and Novosibirsk experts came to the same conclusion as Omsk - the unusual color of the snow is due to the presence of clay-sand dust, which could get into the Omsk region from Kazakhstan. No toxic substances were found in the snow.
March 2008 yellow snow fell in the Arkhangelsk region. Experts suggested that the yellow color of the snow is due to natural factors. This is due to the high content of sand that got into the clouds as a result of dust storms and tornadoes that occurred elsewhere on the planet.
The Pambak River in the Lori region in northern Armenia has acquired a reddish hue, water samples were taken for examination.
April 1999 after the NATO bombing of Yugoslavia and the destruction of petrochemical enterprises, a poisonous "black rain" passed over the town of Pancevo, containing a huge amount of heavy metals and organic compounds harmful to human life. Soil and groundwater were seriously polluted, which turned out to be contaminated with ethylene and chlorine. A huge amount of oil, oil products, ammonia and amino acids got into the Danube.
June-July 2000 in some regions of Dagestan and North Ossetia, in particular, in the city of Vladikavkaz, there were "colored rains". As a result of analyzes of water samples, an increased content of chemical elements was found. They exceeded the maximum allowable concentrations of cobalt (more than four times) and zinc (more than 434 times). Laboratory studies confirmed that the composition of the polluted rain was identical to the chemical composition of the samples taken on the territory of JSC "Electrozinc", which violated the standards for maximum allowable emissions into the atmosphere, approved by the Ministry of Environmental Protection.
In 2000 and 2002"rusty" precipitation fell in the Altai Territory and the Altai Republic. The weather anomaly was caused by strong emissions of combustion products at the Ust-Kamenogorsk metallurgical plant.
July-September 2001"red rains" repeatedly fell out in the Indian state of Kerala. Several hypotheses of the origin of red particles were put forward at once: someone considered them to be red dust carried by the wind from the Arabian Desert, someone recognized them as fungal spores or ocean algae. A version of their extraterrestrial origin was put forward. According to scientists, a total of about 50 tons of this strange substance fell on the ground along with precipitation.
In October 2001 residents of the southwestern regions of Sweden fell under abnormal rain. After the rain, gray-yellow stains remained on the surface of the earth. Swedish experts, and in particular a researcher from the Gothenburg Geoscience Center Lars Fransen, said that strong winds "druck" red sand dust from the Sahara, raised it to a height of up to 5 thousand meters and then poured it along with the rain in Sweden.
Summer 2002 green rain poured over the Indian village of Sangranpur near the city of Kolkata. Local authorities announced that there was no chemical attack. The examination of scientists who arrived at the site determined that the green cloud is nothing more than pollen from flowers and mangoes contained in bee excrement, and does not pose a danger to humans.
In 2003 in Dagestan, precipitation in the form of salt deposits fell. Cars standing in the open air were covered with a layer of salt. According to meteorologists, the reason for this was a cyclone that came from the regions of Turkey and Iran. Fine particles of sand and dust raised by a strong wind from the developed quarries in the territory of Dagestan mixed with water dust raised from the surface of the Caspian Sea. The mixture was concentrated in clouds that moved to the coastal regions of Dagestan, where unusual rain fell.
Winter 2004 orange-colored snow fell in eastern Poland. At the same time, residents of Transcarpathia observed him in the villages of Quiet and Gusinoe. According to one version, sandstorms in Saudi Arabia became the reason for the orange color of the snow: grains of sand, picked up by a strong wind, accumulated in the upper atmosphere and fell along with snow in Transcarpathia.
April 19, 2005 red rain fell in Kantemirovskiy and Kalacheevskiy districts of the Voronezh region. Precipitation left an unusual trace on the roofs of houses, fields, agricultural machinery. In a soil sample, traces of ocher, a natural pigment for paint production, were found. It contained hydroxides of iron and clay. Further investigation revealed that there had been a release at the ocher factory in the village of Zhuravka, which caused the rain clouds to turn red. According to experts, the precipitation did not pose a danger to the health of people and animals.
April 19, 2005 over several regions of the Stavropol Territory, the sky acquired a yellowish tint, and then it began to rain, the drops of which were colorless. After drying, the drops were left on cars and on dark beige clothes, which were not washed off afterwards. The same rain fell on April 22 in Orel. The analyzes carried out showed that the sediments contained alkali, namely, nitrogenous compounds. The precipitation was very concentrated.
April 2005 for several days, orange rains were falling in Ukraine - in the Nikolaev region and in the Crimea. Colored precipitation also covered Donetsk, Dnepropetrovsk, Zaporozhye, Kherson regions these days. Ukrainian weather forecasters said that the orange color of the rain acquired due to a dust hurricane. The wind brought dust particles from North Africa.
February 2006 gray-yellow snow fell on the territory of the village of Sabo, located 80 km south of the city of Okha in the north of Sakhalin. According to eyewitnesses, oily spots of a gray-yellow color and with an unusual strange smell formed on the surface of the water obtained by melting suspicious snow. Experts believe that unusual precipitation could be the consequences of the activity of one of the Far Eastern volcanoes. Possibly, the pollution of the environment by products of the oil and gas industry is to blame. The reason for the yellowing of the snow was not exactly established.
February 24-26, 2006 in some areas of Colorado (USA) it was brown snow, almost like chocolate in color. "Chocolate" snow in Colorado - a consequence of a long drought in neighboring Arizona: there are giant clouds of dust that mixes with snow. Sometimes volcanic eruptions give the same result.
March 2006 creamy-pink snow fell in the north of Primorsky Krai. Experts explained the unusual phenomenon by the fact that the cyclone had previously passed through the territory of Mongolia, where strong dust storms raged at that time, covering large expanses of desert territories. Dust particles were drawn into the vortex of the cyclone and colored the precipitation.
March 13, 2006 in South Korea, including Seoul, yellow snow fell. The snow was yellow because it contained yellow sand brought from the deserts of China. The country's meteorological service has warned that snow containing fine sand can be dangerous for the respiratory system.
November 7, 2006 in Krasnoyarsk, light snow fell with green rain. He walked for about half an hour and, having melted, turned into a thin layer of greenish clay. People exposed to green rain experienced tearing and headaches.
January 31, 2007 in the Omsk region, on an area of \u200b\u200babout 1.5 thousand square kilometers, yellow-orange snow fell with a pungent odor, covered with oily spots. Having passed through the entire Irtysh region, a plume of yellow-orange precipitation touched the Tomsk region along the edge. But the main part of the "acidic" snow fell in the Tarsky, Kolosovsky, Znamensky, Sedelnikovsky and Tyukalinsky districts of the Omsk region. In colored snow, the norm of iron content was exceeded (according to preliminary laboratory data, the concentration of iron in snow was 1.2 mg per cubic centimeter, while the maximum allowable norm was 0.3 mg). According to Rospotrebnadzor, such a concentration of iron is not dangerous for human life and health. Abnormal precipitation was studied by laboratories in Omsk, Tomsk and Novosibirsk. At first it was assumed that the snow contained the poisonous substance heptyl, which is a component of rocket fuel. The second version of the appearance of yellow precipitation was the emissions of the metallurgical enterprises of the Urals. However, Tomsk and Novosibirsk experts came to the same conclusion as Omsk - the unusual color of the snow is due to the presence of clay-sand dust, which could get into the Omsk region from Kazakhstan. No toxic substances were found in the snow.
March 2008 yellow snow fell in the Arkhangelsk region. Experts suggested that the yellow color of the snow is due to natural factors. This is due to the high content of sand that got into the clouds as a result of dust storms and tornadoes that occurred elsewhere on the planet.
Let's imagine the following situation:
You work in a lab and decide to do an experiment. To do this, you opened the cabinet with reagents and suddenly saw the following picture on one of the shelves. Two jars of reagents had their labels peeled off, which were safely left lying nearby. At the same time, it is no longer possible to determine exactly which jar corresponds to which label, and the external signs of the substances by which they could be distinguished are the same.
In this case, the problem can be solved using the so-called qualitative reactions.
Qualitative reactions called such reactions that allow you to distinguish one substance from another, as well as to find out the qualitative composition of unknown substances.
For example, it is known that the cations of some metals, when their salts are added to the burner flame, color it in a certain color:
This method can only work if the substances to be distinguished change the color of the flame in different ways, or one of them does not change color at all.
But, let's say, as luck would have it, the substances you determine do not color the color of the flame, or color it in the same color.
In these cases, it will be necessary to distinguish substances using other reagents.
In what case can we distinguish one substance from another with the help of any reagent?
There are two options:
- One substance reacts with the added reagent, while the other does not. At the same time, it must be clearly visible that the reaction of one of the starting substances with the added reagent has really passed, that is, some external sign of it is observed - a precipitate has formed, a gas has been released, a color change has occurred, etc.
For example, it is impossible to distinguish water from a sodium hydroxide solution using hydrochloric acid, despite the fact that alkalis react perfectly with acids:
NaOH + HCl \u003d NaCl + H 2 O
This is due to the absence of any external signs of a reaction. A transparent colorless solution of hydrochloric acid, when mixed with a colorless hydroxide solution, forms the same transparent solution:
But on the other hand, water can be distinguished from an aqueous solution of alkali, for example, using a solution of magnesium chloride - a white precipitate forms in this reaction:
2NaOH + MgCl 2 = Mg(OH) 2 ↓+ 2NaCl
2) Substances can also be distinguished from each other if they both react with the added reagent, but do so in different ways.
For example, a solution of sodium carbonate can be distinguished from a solution of silver nitrate using a solution of hydrochloric acid.
hydrochloric acid reacts with sodium carbonate to release a colorless, odorless gas - carbon dioxide (CO 2):
2HCl + Na 2 CO 3 \u003d 2NaCl + H 2 O + CO 2
and with silver nitrate to form a white cheesy precipitate AgCl
HCl + AgNO 3 \u003d HNO 3 + AgCl ↓
The tables below show different options for detecting specific ions:
Qualitative reactions to cations
| Cation | Reagent | Sign of reaction |
| Ba 2+ | SO 4 2- | Ba 2+ + SO 4 2- \u003d BaSO 4 ↓ |
| Cu2+ | 1) Precipitation of blue color: Cu 2+ + 2OH - \u003d Cu (OH) 2 ↓ 2) Precipitation of black color: Cu 2+ + S 2- \u003d CuS ↓ |
|
| Pb 2+ | S2- | Precipitation of black color: Pb 2+ + S 2- = PbS↓ |
| Ag+ | Cl- | Precipitation of a white precipitate, insoluble in HNO 3, but soluble in ammonia NH 3 H 2 O: Ag + + Cl − → AgCl↓ |
| Fe2+ | 2) Potassium hexacyanoferrate (III) (red blood salt) K 3 | 1) Precipitation of a white precipitate that turns green in air: Fe 2+ + 2OH - \u003d Fe (OH) 2 ↓ 2) Precipitation of a blue precipitate (turnbull blue): K + + Fe 2+ + 3- = KFe↓ |
| Fe3+ | 2) Potassium hexacyanoferrate (II) (yellow blood salt) K 4 3) Rhodanide ion SCN − | 1) Precipitation of brown color: Fe 3+ + 3OH - \u003d Fe (OH) 3 ↓ 2) Precipitation of a blue precipitate (Prussian blue): K + + Fe 3+ + 4- = KFe↓ 3) The appearance of intense red (blood red) staining: Fe 3+ + 3SCN - = Fe(SCN) 3 |
| Al 3+ | Alkali (hydroxide amphoteric properties) | Precipitation of a white precipitate of aluminum hydroxide when a small amount of alkali is added: OH - + Al 3+ \u003d Al (OH) 3 and its dissolution upon further addition: Al(OH) 3 + NaOH = Na |
| NH4+ | OH − , heating | Emission of gas with a pungent odor: NH 4 + + OH - \u003d NH 3 + H 2 O Blue wet litmus paper |
| H+ (acid environment) | Indicators: − litmus − methyl orange | Red staining |