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Questions tagged [color]

Questions where color (wavelengths associated with the visible region of the electromagnetic spectrum of about 400-800nm), or a color change is discussed.

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33 views

Comparing the emission spectrum of ethanol and mixture of alcohols

Sorry if this question has a simple answer, but I've been unable to find it elsewhere. Using a diffraction grating, burning ethanol (99.9%) will produce a rainbow of colours. However, when burning ...
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27 views

Two common fluids that don't mix inside a labyrinth [closed]

I'm not sure in which SE site put this question. Imagine a typical child toy, where a bunch of spheres move by gravity through a labyrinth. Now imagine a sealed small labyrinth with two fluids. I'd ...
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35 views

When can colourimetry be used to determine the rate of reaction?

Can colourimetry be used if a coloured reactant react to give a coloured product? For example, in the reaction of reacting dichromate ions with oxalate ions in acidic environment, where dichormate ...
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92 views

Why does blood turn reddish brown?

Why does blood take on such a colour after a couple of hours? Is this the iron in my blood being oxidised to iron (III) oxide or is this something else? I have checked this article, and no I do not ...
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103 views

White compound, insoluble in water, turns pink and then white again on adding water

Which white, ionic compound(s) that is insoluble in water turns pink when you add only a little of water but white again when you add more water? I know that the cation is one of the following: $$\...
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1answer
514 views

Material that changes color when changing phase from solid to liquid [closed]

I was asked and am wondering myself, what are materials that change color when molten? I could not find any examples online, but it really interests me. I would to get some examples which have one ...
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465 views

Why do transition metals make colored compounds despite the remaining d orbitals being hybridized? [closed]

I know that transition metals make colored compounds when they forms a bond with a ligand, as the ligand increases the energy level of $\ce{d_{x^2-y^2}}$ and $\ce{d_{z^2}}$ orbital by repelling these ...
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104 views

How to rationalize the colour change of the thermochromic bis(diethyl-ammonium) tetrachloridocuprate(II) complex

The colour of the compound changes from deep green/green-blue to yellow upon raising the temperature. I'm trying to rationalise this by using the d-orbital splitting, but I've got myself in a logic ...
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33 views

How to safely change the color of a fire tornado?

So I've been watching a lot of fire tornado videos and I came across one that had a reasonable and safe setup (around the 3:23 mark): Fire Tornado DIY Is there a way to change the color of the fire ...
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110 views

How do colour pigments chemically work? [closed]

How do color pigments colour the plastics? Is there any chemical reaction, molecular association, or physical reaction? What kind of bonding mechanism is there between pigment molecules and plastics? ...
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56 views

Krazy Glue Color Change

A type of Krazy Glue changes from purple to clear when it dries. What is the chemistry behind the color change? Is it due to a particular compound only found in this particular Glue? A description of ...
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375 views

Why does acetic acid combined with dirt turn blue? [closed]

Around my faucet was some mysterious dirt from a previous tenant. I poured acetic acid with a concentration of 25 percent over it. I came back after a few hours and noticed some blue stains which hadn'...
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57 views

Coordination Chemistry: Predict colors (simple model, old)

I remember many years ago, when I prepared for a talk on coordination chemistry I found a PDF with a theory about how to predict the colors of simple coordination compounds. I remember the name of the ...
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0answers
152 views

Problem in Colour in Cerium (IV)Sulphate due to charge transfer

My text says that $\ce{Ce(SO4)2}$ is coloured due to charge transfer spectra. It also gives other examples such as $\ce{KMnO_4}$ and $\ce{K_2Cr_2O_7}$, to which I agree but when I read the conditions ...
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453 views

Ultramarine blue colour absorbing agent

Ultramarine blue ($\ce{Na2Al2SiO8 + Na2S}$, a sulfide-silicate complex containing sodium and aluminium) is insoluble when mixed in water and gives a blue color appearance to the water solution. ...
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107 views

Are there art supplies that create a new color by mixing through a chemical reaction?

When two elements or compounds react together, they form new compounds, which more often than not assume new colors. If the two elements or compounds don't react, they form uniform or non-uniform ...
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1answer
366 views

Material to change its color by temperature condition meets over time

There are thermochromic materials which their color changes reversible by temperature. Simply they show their current temperature by color. We can say their color is a function of current temperature: ...
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0answers
346 views

What gives variations in the color of cadmium sulfide paint pigment?

Oil paint manufacturers sometimes make several "shades" of a color, all of which list the exact same chemical ingredient. For example, look at Gamblin's artist grade oils, in the yellow colors, ...
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129 views

Why is tin(IV) iodide bright orange while elemental iodine is violet? [duplicate]

Does it have anything to with iodines polarizability? Is there a way to explain this using sigma bonding or an MO diagram?
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29 views

Why are certain substances clear/invisible? Can we create invisible objects? [duplicate]

This is more so a question of how light interacts with matter. For example, why are substances like oxygen generally invisible? If the light hitting the molecules were absorbed, it would appear black, ...
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53 views

Origin of different colour for thio analogue of indigo from blue to red

Why the thio analogue of indigo is red? What is the reason behind change of colour from indigo to red just by change of N to S. What I get is that there will be electronegativity, lone pair ...
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771 views

Predict flame test color?

If you know the composition of any sample of compound, is it possible to predict it's flame test color? For eg, if you can given Sodium Chloride, then without actually doing the flame test, can you ...
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37 views

Reason behind ZnO color [duplicate]

Why is zinc oxide yellow when hot and white when cold? Is it yellow because of the flame used to make it hot?
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297 views

why colour of CuSO4 and CuCl3 is different? [duplicate]

These two are simple ionic compounds , not complexes [if I do not consider water of hydration] then how can I rationalise the difference in colour?
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59 views

How to choose a colorant for a given substrate?

I know there are volumes of International Colour Index (homepage, wiki, paper), but I can't really extract from there for example what red colorants are compatible with both silk and polyester, etc. ...
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3answers
158 views

When an electron returns to it's ground state does it release the same wavelength of light that promoted it in the first place?

If this is true, I fail to understand why we see colour at all -- wouldn't any wavelengths absorbed by electron promotion be inconsequential to colour because there would an equal amount, and ...
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1answer
2k views

Does Nitrogen dioxide change colour if we put it in a constant temperature of e.g. 100 kelvin?

The changing of the colour of $\ce{NO2}$ is because of a change in temperature, resp. heating and cooling?
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1answer
2k views

What is the colour of chromium(III) chloride solution?

I had a question asking about the colour of the solution of chromium(III) chloride in my exam, all my colleagues have different answers, I couldn't find any exact answer after searching!
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1answer
5k views

What is the color of elemental silver?

From my lab book it says it is black? I don't understand how we know the color of it is black. Can anyone explain?
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1answer
338 views

Why does the colour of gold sol change with particle size? [duplicate]

Regarding the colour of gold sol, my book says Finest gold sol is red in colour; as the size of particles increases, it appears purple, then blue and finally golden. This is the image I found on ...
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1answer
123 views

Why does the addition of oxygen render materials colourless? [closed]

In our book, it is mentioned that $\ce{H2O2}$ (hydrogen peroxide) is used as a bleaching agent because of its oxidizing nature: \begin{align} \ce{H2O2 &-> H2O + [O]}\\ \ce{\text{coloured ...
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2answers
722 views

How are electrons in conjugated molecules excited? [duplicate]

I have recently started reading about colour in organic molecules and come across conjugation of pi bonds. My question is pretty short... In transition metal ions I understand colour is caused by ...
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1answer
46 views

Pigmentation of aromates [closed]

So, they try to color naftalene, nitrobenzeen and benzene. Only one of them colors. They can say with certainty that this is nitrobenzeen. Right/wrong and why? Sorry if my English isn't that great, ...
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1answer
222 views

Why does the gas from dry ice flow down?

I am reading Dan Broughton's answer in replying to the question "why does the gas from dry ice flow down" here. According to the answer, the fog is water's color and water is condensed and suspended ...
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1answer
2k views

Why is Sodium Chloride White? [closed]

Why is solid sodium chloride white - and for that matter, why are the majority of salts white in solid form?
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1answer
712 views

Potassium Manganate and Acidified Potassium Dichromate colour changes [closed]

I would be obliged if somebody could explain the colour changes for the reduction of potassium manganate and acidified potassium dichromate. I understand that for potassium manganate, it is being ...
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1answer
1k views

Ethanol discolored yellow when stored with a rubber stopper. Forming fine white precipitate when added to water

I stored some Klean-Strip denatured alcohol in a test tube and capped it with a rubber stopper. I did this in preparation for a chemistry demonstration. When I opened my kit a few days later at the ...
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2answers
2k views

How can we predict the colour of transition metal complexes?

I am facing problems in indentifying colour of complex compunds just by seeing the their molecular formula. Is there any method or concept to predict the colour of complex compunds?
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1answer
510 views

Why does mixing inks make subractive colors?

I have little knowledge of color theory and chemistery. Recently I came to know that printers use CMYK colored inks and combine them in different proportions to achieve any color on print. Let us ...
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1answer
85 views

The color black [closed]

If a perfectly black object were present and it had a rough texture with bumps and crinkles, would it reflect any light? And can black reflect any light?
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1answer
51 views

Why is the reason for color different in these two cases? [closed]

I have read in a book (NCERT India) about flame color for salts of alkali metal and color of transition metal complexes. In the first case, it says that during excitation of electrons to higher ...
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2answers
881 views

What causes the yellow colour in the Briggs-Rauscher oscillating reaction?

The color changes are due to different concentrations of supposedly $\ce{I2}$ (which causes the yellow/amber color), $\ce{I-}$ (colorless) and $\ce{I3-}$ (dark blue). Since iodine ($\ce{I2}$) is ...
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1answer
3k views

Why flame color of salts is determined by metal

If a pure metal is heated up in a flame, we see it giving the flame a characteristic color, e.g. $\ce{Na}$ burns yellow. If a salt, e.g. $\ce{NaCl}$ or $\ce{Na2SO4}$, is heated up, resulting color to ...
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1answer
366 views

How does the degree of saturation influence the colour of the flame?

If the colour of flame produced by the atom of an element is the property of that element then why do unsaturated and saturated carbon compounds give different colours of flame even though both ...
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1answer
3k views

How to Determine An Element's Colour

Different elements have different colours. Some elements may have similar colours like Sodium (Na) and Potassium (K), so that's why i'm asking "is there a way to calculate or even simply deduce the ...
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2answers
566 views

Are there biodegradable pigments that are soluble in oil, but not in water?

I'm hoping to find a purple pigment that preferably, but not necessarily, can be used at room temperature. The goal is a pigment that will break down in septic systems.
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1answer
953 views

How to change color of water based on its acidity?

I recently saw a video on YouTube in which water, when mixed with a solution (I believe iodine was involved,) changed color based on its acidity. I am attempting to replicate this experiment, but ...
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1answer
161 views

Where can I find a complete and accurate table of CPK colours?

I have been using several chemical drawing softwares including MarvinSketch, Jmol, Accelrys DS Visualizer, Avogadro, etc., all of which I have set to CPK colouring. Despite this supposedly common ...
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0answers
19 views

What solvents can solve aromatic urethane resins?

Do you have any information about chemical resistance of hexa-functional aromatic urethane acrylate? I want to know what solvents can solve aromatic urethane resins.
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0answers
49 views

Does something like a fluorescent foil or a fluorescent film exist?

During my experiments I want the emitted laser beams to come back with a different wavelength than the original wavelength using a fluorescent foil or fluorescent film. The laser I'm currently using ...