Which element burns with a yellow flame. Why is the flame of fire first blue and then yellow?

It's easy to guess that flame color will depend on what chemicals burn in it, if under the influence of high temperature individual atoms of these substances are released - giving color. Many experiments have been carried out, which I will write about below, in order to understand how substances affect fire color.

Even in ancient times, scientists and alchemists tried to understand what kind of substances burned in fire, depending on the color of the fire.

Almost everyone at home has gas stoves or water heaters, the flames of which are colored blue tint. This is due to combustible carbon, carbon monoxide, which gives this shade. Sodium salts, which natural wood is rich in, give yellow-orange flame, which is used to burn an ordinary forest fire or household matches. Sprinkling the burner gas stove with regular salt, you will get the same shade. Copper gives green color flame. I think you have noticed more than once that ordinary, unprocessed protective composition, copper stains the skin green tint, if you wear a ring or chain for a long time. So it is during the combustion process. With a high copper content, the flame has a very bright green color, almost identical to white. You can observe this by sprinkling copper shavings on the same gas burner.

Experiments were carried out with a conventional gas burner and various minerals in order to determine their composition. The mineral is taken with tweezers and brought into the flame - by the shade in which the fire is painted, one can judge the various impurities present in the element. Green and its shades are given by such minerals as barium, copper, molybdenum, phosphorus, antimony and boron, which gives blue-green color. also in blue Selenium colors the flame. Red the flame will give lithium, strontium and calcium, purple– potassium, yellow-orange the shade comes out when sodium burns.

To study minerals and determine their composition, it is used Bunsen burner, giving an even, colorless flame color that does not interfere with the course of the experiment, invented by Bunsen in the middle of the 19th century.

Bunsen was an ardent admirer of the fire element, often tinkering with flames. His hobby was glassblowing. By blowing various cunning designs and mechanisms out of glass, Bunsen could not notice the pain. There were times when his calloused fingers began to smoke from the hot, still soft glass, but he did not pay attention to it. If the pain had already gone beyond the threshold of sensitivity, then he saved himself using his own method - he pressed his earlobe tightly with his fingers, interrupting one pain with another.

It was he who was the founder of the method determining the composition of a substance by the color of the flame. Of course, before him, scientists tried to carry out such experiments, but they did not have a Bunsen burner with colorless flame, not interfering with the experiment. He introduced the burner into the flame various elements on platinum wire, since platinum does not affect the color of the flame and does not color it.

It would seem that the method is good, there is no need for complex chemical analysis; bring the element to the flame and its composition is immediately visible. But it was not there. Very rarely substances are found in nature in pure form, they usually contain a large set of various impurities, changing color.

Tried Bunsen various methods identifying colors and their shades. For example, I tried look through colored glass. Let's say blue glass extinguishes the yellow color produced by the most common sodium salts, and the crimson or purple tint of the native element could be distinguished. But even with the help of these tricks it was possible to determine the composition of a complex mineral only once in a hundred.

Very beautiful scientific experiment from Professor Nicolas" Colored flame" allows you to get the flame of four different colors, using the laws of chemistry for this.

The set is most interesting, we really saw enough of the flames, amazing sight! It’s interesting for everyone: both adults and children, so I highly recommend it! The advantage is that this experiment with fire can be done at home, you don’t have to go outside. The set includes cups and bowls in which a tablet of dry fuel burns, everything is safe, and wooden floor(or table) can be placed.

It is better, of course, to conduct the experiment under adult supervision. Even if the children are already quite big. Fire is still a dangerous thing, but at the same time... creepy (this is the word that fits here very accurately!) interesting!! :-))

See photos of the set packaging in the gallery at the end of the article.

The Colored Flame kit contains everything you need to carry out the experiment. The set includes:

• potassium iodide,
• calcium chloride,
• hydrochloric acid solution 10%,
• copper sulfate,
• nichrome wire,
• copper wire,
• sodium chloride,
• dry fuel, evaporation cup.

The only thing I have some complaints about is the manufacturer - I expected to find a mini-brochure with a description in the box chemical process, which we see here, and an explanation of why the flame becomes colored. There was no such description here, so you’ll have to turn to the chemistry encyclopedia (). If, of course, there is such a desire. And older children, of course, have a desire! Younger children, of course, do not need any explanations: they are simply very interested in watching how the color of the flame changes.

On back side The packaging box says what needs to be done to make the flame become colored. At first they did it according to the instructions, and then they just started sprinkling the flames with different powders from jars (when they were sure that everything was safe) :-)) - the effect was amazing. :-) Flashes of red flame in yellow, bright light green flame, green, purple... the sight is simply mesmerizing.

It’s very cool to buy for some holiday, it’s much more interesting than any firecracker. And on New Year it will be very cool. We burned during the day; it would have been even more spectacular in the dark.

We still have the reagents left after burning one tablet, so if we take another tablet (purchase separately), we can repeat the experiment. The clay cup washed quite well, so it will be enough for many experiments. And if you are at the dacha, then the powder can be sprinkled on the fire in the fire - then, of course, it will quickly end, but the spectacle will be fantastic!

I add brief information about the reagents that come with the experiment. For curious kids who are interested in learning more. :-)

Flame coloring

The standard method of coloring a faintly luminous gas flame is to introduce metal compounds into it in the form of highly volatile salts (usually nitrates or chlorides):

yellow - sodium,

red - strontium, calcium,

green - cesium (or boron, in the form of boronethyl or boronmethyl ether),

blue - copper (in the form of chloride).

Selenium colors the flame blue, and boron colors the flame blue-green.

The temperature inside the flame is different and changes over time (depending on the influx of oxygen and combustible substance). Blue color means that the temperature is very high up to 1400 C, yellow means the temperature is slightly lower than when blue flame. The color of the flame may vary depending on chemical impurities.

The color of a flame is determined only by its temperature, if you do not take into account its chemical (more precisely, elemental) composition. Some chemical elements are capable of coloring the flame in a color characteristic of this element.

In laboratory conditions, it is possible to achieve a completely colorless fire, which can only be determined by the vibration of the air in the combustion area. Household fire is always “colored”. The color of a fire is determined by the temperature of the flame and what chemicals it burns. Heat flame allows atoms to jump for some time to a higher energy state. When the atoms return to their original state, they emit light at a specific wavelength. It corresponds to the structure of the electronic shells of a given element.

Gblue the flame, for example, that can be seen when natural gas burns, is caused by carbon monoxide, which gives the flame its hue. Carbon monoxide, whose molecule consists of one oxygen atom and one carbon atom, is a byproduct of the combustion of natural gas.

Potassium - violet flame

1) B green color flame boric dyes acid or copper (brass) wire dipped in salt acid.

2) Red flame colors chalk dipped in the same salt acid.

When strongly calcined in thin fragments, Ba-containing (Barium-containing) minerals color the flame yellow-green. The coloring of the flame can be enhanced if, after preliminary calcination, the mineral is moistened in strong hydrochloric acid.

Copper oxides (in experience for green flame hydrochloric acid and copper crystals are used) give an emerald green color. Calcined Cu-containing compounds moistened with HC1 color the flame azure blue CuC1 2). The reaction is very sensitive.

Green color and barium, molybdenum, phosphorus, and antimony also give its shades to fire.

Copper nitrate and hydrochloric acid solutions are blue or green; When ammonia is added, the color of the solution changes to dark blue.

Yellow flame - salt

For yellow flame cooking supplement required salt, sodium nitrate or sodium chromate.

Try sprinkling a little table salt on the burner of a gas stove with a transparent blue flame - yellow tongues will appear in the flame. This yellow-orange flame give sodium salts (a salt, remember, this is sodium chloride).

Yellow is the color of sodium in the flame. Sodium is found in any natural organic material, which is why we usually see the flame yellow. And yellow color can drown out other colors - this is a feature of human vision.

Yellow flames appear when sodium salts decompose. Wood is very rich in such salts, so an ordinary forest fire or household matches burn with a yellow flame.

Blacker than black

Figure 1 - Model of a completely black body.

Light entering through the hole will be completely absorbed after repeated reflections, and the outside of the hole will appear completely black. Even if we paint the cube black, the hole will be blacker than the black cube. This hole will be completely black body. IN literally words, the hole is not a body, but only clearly demonstrates we have a completely black body.
All objects emit heat (as long as their temperature is above absolute zero, which is -273.15 degrees Celsius), but no object is a perfect heat emitter. Some objects emit heat better, others worse, and all this depends on various conditions environment. Therefore, a black body model is used. A completely black body is ideal heat emitter. We can even see the color of a completely black body if it is heated, and the color we will see, will depend on what temperature We let's heat it up absolutely black body. We have come close to the concept of color temperature. Look at Figure 2.

Figure 2 - The color of an absolutely black body depending on the heating temperature.

A) There is an absolutely black body, we don’t see it at all. Temperature 0 Kelvin (-273.15 degrees Celsius) - absolute zero, the complete absence of any radiation.
b) Turn on the “super-powerful flame” and begin to heat up our absolutely black body. The body temperature, through heating, increased to 273K.
c) A little more time has passed and we already see a faint red glow of a completely black body. The temperature increased to 800K (527°C).
d) The temperature rose to 1300K (1027°C), the body acquired bright red color. You can see the same color glow when heating some metals.
e) The body has heated up to 2000K (1727°C), which corresponds to an orange glow. Hot coals in a fire, some metals when heated, and a candle flame have the same color.
f) The temperature is already 2500K (2227°C). The glow at this temperature becomes yellow. Touching such a body with your hands is extremely dangerous!
g) White color - 5500K (5227°C), the same color of the glow of the Sun at noon.
h) Blue color of the glow - 9000K (8727°C). In reality, it will be impossible to obtain such a temperature by heating with a flame. But such a temperature threshold is quite achievable in thermonuclear reactors, atomic explosions, and the temperature of stars in the universe can reach tens and hundreds of thousands of Kelvin. We can only see the same blue tint of light, for example, in LED lights, celestial bodies or other light sources. The color of the sky in clear weather is approximately the same color. Summarizing all of the above, we can give a clear definition of color temperature. Colorful temperature is the temperature of a black body at which it emits radiation of the same color tone as the radiation in question. Simply put, 5000K is the color that a blackbody becomes when heated to 5000K. The color temperature of orange is 2000K, which means that a completely black body must be heated to a temperature of 2000K for it to acquire Orange color glow.
But the color of the glow of a hot body does not always correspond to its temperature. If there is a gas stove flame in the kitchen blue-blue color, this does not mean that the flame temperature is above 9000K (8727°C). Molten iron in its liquid state has an orange-yellow hue, which actually corresponds to its temperature, which is approximately 2000K (1727°C).

Color and its temperature

Figure 3 - Color temperature of xenon automobile lamps.

Figure 4 - Color temperature of fluorescent lamps.

On Wikipedia I found numerical values ​​for the color temperatures of common light sources:
800 K - the beginning of the visible dark red glow of hot bodies;
1500-2000 K - candle flame light;
2200 K - incandescent lamp 40 W;
2800 K - 100 W incandescent lamp (vacuum lamp);
3000 K - incandescent lamp 200 W, halogen lamp;
3200-3250 K - typical film lamps;
3400 K - the sun is at the horizon;
4200 K - fluorescent lamp (warm white light);
4300-4500 K - morning sun and lunchtime sun;
4500-5000 K - xenon arc lamp, electric arc;
5000 K - sun at noon;
5500-5600 K - photo flash;
5600-7000 K - fluorescent lamp;
6200 K - close to daylight;
6500 K - standard source of daytime white light, close to midday sunlight; 6500-7500 K - cloudy;
7500 K - daylight, with a large share of scattered light from a clear blue sky;
7500-8500 K - twilight;
9500 K - blue clear sky on the north side before sunrise;
10,000 K is an “infinite temperature” light source used in reef aquariums (anemone blue tint);
15,000 K - clear blue sky in winter;
20,000 K - blue sky in polar latitudes.
Color temperature is source characteristics Sveta. Any color we see has a color temperature and it doesn’t matter what color it is: red, crimson, yellow, purple, violet, green, white.
Works in the field of studying the thermal radiation of a black body belong to the founder of quantum physics, Max Planck. In 1931, at the VIII session of the International Commission on Illumination (CIE, often written as CIE in the literature), it was proposed color model XYZ. This model is a chromaticity diagram. The XYZ model is shown in Figure 5.

Figure 5 - XYZ chromaticity diagram.

The X and Y numeric values ​​define the color coordinates on the chart. The Z coordinate determines the brightness of the color, it is in this case is not involved, since the diagram is presented in two dimensions. But the most interesting thing in this figure is the Planck curve, which characterizes the color temperature of the colors on the diagram. Let's take a closer look at it in Figure 6.

Figure 6 - Planck Curve

The Planck curve in this figure is slightly truncated and “slightly” inverted, but this can be ignored. To find out the color temperature of a color, you simply need to extend the perpendicular line to the point of interest (color area). The perpendicular line, in turn, characterizes such a concept as bias- degree of color deviation to green or purple. Those who have worked with RAW converters know such a parameter as Tint - this is the offset. Figure 7 displays the color temperature adjustment panel in RAW converters such as Nikon Capture NX and Adobe CameraRAW.

Figure 7 - Panel for setting color temperature for different converters.

It's time to look at how the color temperature is determined not just of an individual color, but of the entire photograph as a whole. Take, for example, a rural landscape on a clear sunny afternoon. Who has practical experience in photography, knows that the color temperature at solar noon is approximately 5500K. But few people know where this figure came from. 5500K is the color temperature the whole stage, i.e. the entire image under consideration (picture, surrounding space, surface area). Naturally, an image consists of individual colors, and each color has its own color temperature. What you get: blue sky (12000K), foliage of trees in the shade (6000K), grass in a clearing (2000K), various kinds vegetation (3200K - 4200K). As a result, the color temperature of the entire image will be equal to the average value of all these areas, i.e. 5500K. Figure 8 clearly demonstrates this.

Figure 8 - Calculation of the color temperature of a scene taken on a sunny day.

The following example is illustrated in Figure 9.

Figure 9 - Calculation of the color temperature of a scene filmed at sunset.

The picture shows a red flower bud that seems to be growing from wheat cereal. The picture was taken in the summer at 22:30, when the sun was setting. This image is dominated by a large number of colors are yellow and orange in color tone, although there is a blue tint in the background with a color temperature of approximately 8500K, there is also an almost pure white color with a temperature of 5500K. I took just the 5 most basic colors in this image, matched them to a chromaticity chart, and calculated the average color temperature of the entire scene. This is, of course, approximately, but true. There are a total of 272816 colors in this image and each color has its own color temperature, if we calculate the average for all colors manually, then in a couple of months we will be able to get a value even more accurate than I calculated. Or you can write a program to calculate and get an answer much faster. Let's move on: Figure 10.

Figure 10 - Calculation of color temperature of other lighting sources

The hosts of the show programs decided not to burden us with color temperature calculations and made only two lighting sources: a spotlight emitting white-green bright light and a spotlight that shines with red light, and the whole thing was diluted with smoke... oh, well, yes - and they installed a presenter bring to Front. The smoke is transparent, so it easily transmits the red light of the spotlight and becomes red itself, and the temperature of our red color, according to the diagram, is 900K. The temperature of the second spotlight is 5700K. The average between them is 3300K. The remaining parts of the image can be ignored - they are almost black, and this color does not even fall on the Planck curve on the diagram, because the visible radiation of hot bodies begins at about 800K (red color). Purely theoretically, one can assume and even calculate the temperature for dark colors, but its value will be negligible compared to the same 5700K.
And the last image in Figure 11.

Figure 11 - Calculation of the color temperature of a scene taken in the evening.

Photo taken summer evening after sunset. The color temperature of the sky is located in the region of the blue color tone on the diagram, which, according to the Planck curve, corresponds to a temperature of approximately 17000K. Green coastal vegetation has a color temperature of about 5000K, and sand with algae has a color temperature of about 3200K. The average value of all these temperatures is approximately 8400K.

White balance

Figure 12 - Modes for setting white balance in a photo camera (video camera).

It should be said right away that the white color of objects can be obtained if use source Sveta with color temperature 5500K(this could be sunlight, photoflash, other artificial illuminants) and if the ones themselves are considered objects white (reflect all visible light radiation). In other cases, the white color can only be close to white. Look at Figure 13. It shows the same XYZ chromaticity diagram that we recently looked at, and in the center of the diagram there is a white dot marked with a cross.

Figure 13 - White dot.

The marked point has a color temperature of 5500K and, like true white, it is the sum of all the colors of the spectrum. Its coordinates are x = 0.33 and y = 0.33. This point is called equal energy point. White dot. Naturally, if the color temperature of the light source is 2700K, the white point is not even close, what kind of white color can we talk about? There will never be white flowers there! In this case, only highlights can be white. An example of such a case is shown in Figure 14.

Figure 14 – Different color temperatures.

White balance– this is setting the value color temperature for the entire image. At correct installation you will receive colors that match the image you see. If the resulting image is dominated by unnatural blue and cyan color tones, it means that the colors are “not warmed up enough”, the color temperature of the scene is set too low, it needs to be increased. If the entire image is dominated by a red tone, the colors are “overheated”, the temperature is set too high, it is necessary to lower it. An example of this is Figure 15.

Figure 15 – Example of correct and incorrect color temperature settings

The color temperature of the entire scene is calculated as average temperature all colors given image, so in the case of mixed light sources or very different color tone colors, the camera will calculate average temperature, which is not always true.
An example of one such incorrect calculation is shown in Figure 16.

Figure 16 – Inevitable inaccuracy in setting color temperature

The camera cannot perceive sharp differences in brightness individual elements images and their color temperature are the same as human vision. Therefore, to make the image almost the same as you saw when you took it, you will have to manually adjust it according to your visual perception.

This article is more intended for those who are not yet familiar with the concept of color temperature and would like to learn more. The article does not contain complex mathematical formulas and precise definitions of some physical terms. Thanks to your comments, which you wrote in the comments, I made small amendments to some paragraphs of the article. I apologize for any inaccuracies.

Description:

Wetting a copper plate in hydrochloric acid and bringing it to the burner flame, we notice an interesting effect - coloring of the flame. The fire shimmers with beautiful blue-green shades. The spectacle is quite impressive and mesmerizing.

Copper gives the flame a green tint. With a high copper content in the combustible substance, the flame would have a bright green color. Copper oxides give an emerald green color. For example, as can be seen from the video, when wetting copper hydrochloric acid the flame turns blue with a greenish tint. And calcined copper-containing compounds soaked in acid color the flame azure blue.

For reference: Barium, molybdenum, phosphorus, and antimony also give green color and its shades to fire.

Explanation:

Why is the flame visible? Or what determines its brightness?

Some flames are almost invisible, while others, on the contrary, shine very brightly. For example, hydrogen burns with an almost completely colorless flame; the flame of pure alcohol also shines very weakly, but a candle and a kerosene lamp burn with a bright luminous flame.

The fact is that the greater or lesser brightness of any flame depends on the presence of hot solid particles in it.

Fuel contains carbon in greater or lesser quantities. Carbon particles become heated before they burn, which is why the flame gas burner, a kerosene lamp and a candle shines - because it is illuminated by hot carbon particles.

Thus, it is possible to make a non-luminous or weakly luminous flame bright by enriching it with carbon or heating non-combustible substances with it.

How to get multi-colored flames?

To obtain a colored flame, not carbon is added to the burning substance, but metal salts that color the flame in one color or another.

The standard method of coloring a faintly luminous gas flame is to introduce metal compounds into it in the form of highly volatile salts - usually nitrates (salt nitric acid) or chlorides (salts of hydrochloric acid):

yellow- sodium salts,

red - strontium, calcium salts,

green - cesium salts (or boron, in the form of boronethyl or boronmethyl ether),

blue - copper salts (in the form of chloride).

IN Selenium colors the flame blue, and boron colors the flame blue-green.

This ability of burning metals and their volatile salts to impart a certain color to a colorless flame is used to produce colored lights (for example, in pyrotechnics).

What determines the color of a flame (in scientific language)

The color of a fire is determined by the temperature of the flame and what chemicals it burns. The high temperature of the flame allows atoms to jump to a higher energy state for some time. When the atoms return to their original state, they emit light at a specific wavelength. It corresponds to the structure of the electronic shells of a given element.

The temperature of the fire makes you see familiar things in a new light - a match flashing white, the blue glow of a burner gas stove in the kitchen, orange-red tongues above the flaming wood. A person does not pay attention to the fire until his fingertips are burned. Or it won't burn the potatoes in the frying pan. Or it won’t burn through the soles of sneakers drying over a fire.

When the first pain, fear and disappointment pass, the time for philosophical reflection comes. About nature, color scheme, fire temperature.

Burns like a match

Briefly about the structure of a match. It consists of a stick and a head. Sticks are made from wood, cardboard and cotton cord impregnated with paraffin. The wood chosen is soft species - poplar, pine, aspen. The raw material for sticks is called match straw. To avoid smoldering of the straws, the sticks are impregnated with phosphoric acid. Russian factories make aspen straws.

The head of a match is simple in shape, but complex in its chemical composition. The dark brown match head contains seven components: oxidizing agents - Berthollet salt and potassium dichromate; glass dust, red lead, sulfur, zinc white.

The head of the match ignites when rubbed, heating up to one and a half thousand degrees. Ignition threshold, in degrees Celsius:

• poplar - 468;
• aspen - 612;
• pine - 624.

The temperature of the fire of the match is equal to the temperature of the match. Therefore, the white flash of the sulfur head is replaced by the yellow-orange tongue of the match.

If you look closely at a burning match, you will see three zones of flame. The bottom one is cool blue. The average is one and a half times warmer. The top is the hot zone.

Fire artist

When you hear the word “bonfire,” nostalgic memories flash no less brightly: the smoke of a fire, creating a trusting atmosphere; red and yellow lights, flying towards the ultramarine sky; reeds change from blue to ruby ​​red; crimson cooling coals in which “pioneer” potatoes are baked.

The changing color of a flaming tree indicates fluctuations in the temperature of the fire in the fire. Wood smoldering (darkening) begins at 150°. Fire (smoke) occurs in the range of 250-300°. With the same oxygen supply to the rock at different temperatures. Accordingly, the degree of fire will also be different. Birch burns at 800 degrees, alder at 522°, and ash and beech at 1040°.

But the color of the fire is also determined by the chemical composition of the burning substance. Yellow and orange contribute sodium salts. Chemical composition Cellulose contains both sodium and potassium salts, which give burning wood coals their red tint. Romantic reactions in a wood fire arise due to a lack of oxygen, when instead of CO 2, CO is formed - carbon monoxide.

Enthusiasts scientific experiments measure the temperature of the fire in a fire with a device called a pyrometer. Three types of pyrometers are made: optical, radiation, spectral. These are non-contact devices that allow you to evaluate the power of thermal radiation.

Studying fire in our own kitchen

Kitchen gas stoves operate on two types of fuel:

1. Trunk natural gas methane.
2. Propane-butane liquefied mixture from cylinders and gas holders.

The chemical composition of the fuel determines the fire temperature of a gas stove. Methane, when burned, forms a fire with a power of 900 degrees at the top point.

Combustion of the liquefied mixture produces heat up to 1950°.

An attentive observer will note the uneven coloring of the burner reeds of a gas stove. Inside the fire torch there is a division into three zones:

• Dark area located near the burner: there is no combustion here due to lack of oxygen, and the temperature of the zone is 350°.
• A bright area lying in the center of the torch: the burning gas heats up to 700°, but the fuel does not burn completely due to a lack of oxidizer.
• Translucent upper section: reaches a temperature of 900°, and gas combustion is complete.

The figures for the temperature zones of the fire torch are given for methane.

Safety rules for fire events

When lighting matches or a stove, take care of the ventilation of the room. Provide oxygen flow to the fuel.

Do not attempt to repair it yourself gas equipment. Gas does not tolerate amateurs.

Housewives note that the burners glow blue, but sometimes the fire turns orange. This is not a global temperature change. The color change is due to a change in fuel composition. Pure methane burns colorless and odorless. For safety reasons, sulfur is added to household gas, which, when burned, colors the gas blue and imparts a characteristic odor to the combustion products.

The appearance of orange and yellow shades in the fire of the burner indicates the need for preventive manipulations with the stove. Masters will clean the equipment, remove dust and soot, the combustion of which changes the usual color of the fire.

Sometimes the fire in the burner turns red. This is a signal of dangerous levels of carbon monoxide in the oxygen supply to the fuel is so small that the stove even goes out. Carbon monoxide is tasteless and odorless, and a person is near the source of emissions harmful substance notices too late that he has been poisoned. Therefore, the red color of the gas requires an immediate call to specialists for preventative maintenance and adjustment of the equipment.