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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Paint Changes Color on Stucco. Chemical Reaction is Occurring, but What is Reacting?

PROBLEM: When I apply paint to my home’s exterior stucco(currently white), the paint changes color. The grays change to purple. The whites change to yellow. Greenish-beige becomes orange. I have ...
4
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0answers
23 views

Why is there a difference in the colours of K₂Cr₂O₇ and K₂CrO₄?

In both the compounds the oxidation state of Chromium is +6 so why is there a difference in the colours of their aqueous solutions. $\ce{K2Cr2O7}$ is red-yellow and $\ce{K2CrO4}$ is bright yellow I ...
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0answers
19 views

Why does iodine have different colors in different mediums?

It is violet in trichloromethane, but brown in water. why? In the Shriver Atkins book, they tried to explain this using Molecular Orbital Theory which was not clear to me
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1answer
22 views

Coloration of substances because of F-Centers

In case of metal deficient defects in the crystal lattice of a metal, the positive void are filled by electrons. How does this result in the coloration of a substance? Does this condition arise ...
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1answer
25 views

Color of Phenomelanin?

Do we know what is the wavelength of the color of Phenomelanin? If not, can we use the color of Phenomelanin-rich areas, like the lips, to discern the color of Phenomelanin?
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16 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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0answers
20 views

Why does egg yolk turn white when washed with water?

I recently noticed that whenever I washed the egg yolk stuck on some utensils the water becomes milky white. It has to be the egg yolk that turns white and give off the white color to water right?
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0answers
28 views

How hydrate isomerism results difference in colours?

The standard example is $\ce{CrCl3.6H2O}$, which can have three distinctly different crystalline compounds now known as $\ce{[Cr(H2O)6]Cl3}$ (violet), $\ce{[CrCl(H2O)5]Cl .H2O}$ (blue-green), and ...
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1answer
33 views

Iodine color change in different complexes

Why does the color of iodine differ when it forms a charge transfer complex with benzene (pi donor) - pink and ethanol (electron pair donor) - brown? Does the HOMO-LUMO energy differ, if so how?
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25 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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2answers
507 views

Would it be possible to create a (non-toxic) alcoholic drink that, when zapped with laser, changes color?

Would it be possible to create a (non-toxic) alcoholic drink that, when zapped with a 0.5mW laser pointer, changes color? This would be mainly for the visual effects (bartender show) so it should not ...
2
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1answer
39 views

Mixing Different Solutions with Different Wavelengths to Get Different Colors?

I recently was told that the reason you can mix colors (blue and yellow make green because wavelengths 605nm + 450nm = green) was based on wavelength (which seems very obvious when you think about it ...
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2answers
2k views

Why is snow white?

I know that this is a rather ambiguous question; but my question is, whenever we take water and freeze it in the freezer, it still tends to stay clear. Since snow is just frozen water, why is it ...
3
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1answer
71 views

Why did the solution turn green?

I mixed L Arginine with l Citrulline in Hibiscus and green tea water which was red in color. Once the red liquid hit the mix of powdered Aminoacids the solution changed green. Can someone tell me why? ...
2
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1answer
28 views

Thermochromic pigment that changes at around 50 °C / 120 °F?

I wish to find a pigment that can indicate when a battery contact is getting too hot, and all the thermochromic pigments from hobby stores change color below body temperature, at 31 °C is the highest ...
5
votes
1answer
145 views

Acetone and Sodium Hydroxide

I have put in a beaker acetone and sodium hydroxide solution (approximately 1M $\ce{NaOH}$) and didn't see any colour change for 1 day (actually, it was transparent, no colour). After almost 2 days, ...
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1answer
35 views

How pigments actually function as colorants?

Pigments are insoluble colorants that have no affinity to the substrate. So how can they function as colorants if they "can't stick"? Are pigments always applied together with a "binder"?
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0answers
21 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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1answer
98 views

Are there yellow metals besides gold and copper?

Are there yellow metals besides gold and copper? Are there metals with color different than yellow and grey?
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1answer
35 views

Alcohol spectrophotometry

A couple of weeks ago we did a lab where we had a bunch of standard solutions of alcohol, dichromate, and sulfuric acid. We also had one unknown concentration. We heated them so they would all react, ...
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1answer
156 views

Is it possible to make broad spectrum light absorbing paint?

Is there such a paint / pigment that absorbs most wavelengths of light (beyond the visible light range) that can be used for solar heat generating applications? If not, would it be possible to make ...
6
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1answer
52 views

What are the physical properties affected in ZnO when there is a sulfur impurity?

I have a question. I work at a brass metal foundry where one of our waste products is $\ce{ZnO}$, which we sell. Because we have been making new alloys which contain sulfur, our $\ce{ZnO}$ has a very ...
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1answer
66 views

How does UV affect skin colors in dark-skinned people?

Skin color is one of the things one would rather not ask anything about! Only in humans, it can vary from very dark brown to pale pink. In darker-skinned people, the color is mainly due to melanin, ...
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3answers
129 views

How to make permanent ink that appears after some time?

I'd like to ask, how to make permanent ink, that will be invisible when used, but after like 30 minutes it will appear (preferably dark color)? Thanks.
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1answer
1k views

Does bleach turn a substance white or colorless?

From what I understand, bleach works to weaken the ability of a substance to absorb light. Thus this seems to be "whitening" i.e. reflecting all light. In contrast, colorlessness (according to ...
4
votes
1answer
71 views

why does a glass tube show white bands after being heated with a torch?

When I use a torch to split a glass tube, there's always a hazy white band which appears. Does anyone know what the cause of this is? (FYI, it was a hydrogen-oxygen torch. The glass is fused quartz ...
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1answer
88 views

Ultraviolet acid base indicator

Is there a chemical(s) that provides good discrimination between absorbance curves for different pHs in the UV light spectrum (100-400nm?)
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1answer
88 views

How to change color of urine safely? [closed]

I am trying to find a SAFE way to change the colour of my urine, from what I have read online, Methylene Blue is relatively safe, and will change urine to blue or green. Is it safe? Can I put this in ...
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1answer
37 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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1answer
974 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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0answers
33 views

How can I tell what colour an element will be? [duplicate]

Previously in my Chemistry education, it was required of us to memorise the colour changes some elements, especially transition metals, go through. Currently we learning about electron configuration ...
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1answer
47 views

Fluoride Color Reaction

I am trying to find visual ways to demonstrate water contaminants. For example, chlorine reacts to N,N-diethyl-p-phenyldiamine (DPD), forming a magenta color. The chemical doesn't need to be accurate, ...
3
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1answer
60 views

The walls of a plastic vial with Mercury inside are darkening. What is causing this?

I have a sample of Mercury in a plastic vial, The vial is a BD Vacutainer (genuine), made of polyethylene terephthalate. It is used for blood samples, and the one I used was new. When the vial was ...
3
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1answer
49 views

What is an effective fabric-friendly solvent for aluminium chlorohydrate?

I have recently found out that the white/yellowish "sweat" stains one occasionally finds on t-shirts might be aluminium chlorohydrate polymers. While talk about aluminium and antiperspirants is all ...
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2answers
89 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 ...
2
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1answer
80 views

Why is $\ce Co(SCN)_4$ blue?

Why is $\ce Co(SCN)_4$ blue? I simply can't predict the colors of such inorganic salts. I have learnt that $\ce {Co^{2+}}$ salts are pink in color. Also, if the ligand is a strong field ligand ...
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1answer
136 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
530 views

Flame test: Is the metal atom or the metal ion responsible for the flame colour?

Why is the textbook answer $\ce{Ca}$, why not $\ce{Ca^2+}$ ?
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3answers
936 views

what is the origin of the colour of azo dyes?

what is the origin of the colour of azo-dyes? Is it the same reason as to why transition metal complexes have colour?
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3answers
169 views

How do i find out which species is colourless? [closed]

Among the following $$\ce{TiF6^{2-},\ CoF6^{3-},\ NiCl4^{2-},\ CuCl2}$$ how do i find the species which i colorless If possible please provide the concept used to deduce the result it will be very ...
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3answers
339 views

Why does ZnO turn yellow when it is hot?

Why does ZnO's color become yellow when it is hot? I have read that it is because of physical properties, but I need a more elaborate explanation.
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1answer
415 views

Can I synthesize iron acetate like this?

The oxidation state of the iron doesn't matter too much; I am just trying to make an attractive red-brown ink. Here are some instructions I prescribed to a friend. Here's an approximately decent ...
2
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0answers
110 views

What reaction took place?

Okay, so I was fiddling about in the chemistry lab, and I added: Sodium Nitroprusside (soln) $\ce{Na_2[Fe(CN)_5NO]}$ with Potassium Ferrocyanide (soln) $\ce{K_4[Fe(CN)_6]}$. $\ce{Na_2[Fe(CN)_5NO]}$ ...
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3answers
140 views

Can you colour a flame, and what would the effects be?

I read this question : Flame temperature for cooking food and was thinking, could companies colour there flames so that products would heat quicker? how would they do this, also could you use this to ...
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2answers
136 views

Egg-Detection in Pastries: An Analysis in Heat-Alterated Molecule Identification

I would like to know if anybody here knows of a method to detect the presence of ovalbumin--or any unique, egg-related molecule, in a baked good. Here I am anticipating that the "unique egg-related ...
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1answer
208 views

How Does The Mordant, Ferric Acetate, Interact With Tannins When Ebonizing Wood?

Ferric Acetate (II) and (III) are "mordants," which intensify wood staining in direct proportion to the tannin concentration in the wood. Some wood stainers add tea to increase the tannin content and ...
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3answers
12k views

Why do transition elements make colored compounds?

Why do transition metals element make colored compound both in solid form and in solution? Is it related with their electrons or something else?
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1answer
112 views

Is it possible to calculate chromacity coordinates using absorbance values?

I have absorbance values for blood plasma. Absorbance was measured in range of 380 – 600 nm every 5 nm ending up with absorbance values for 45 wave lengths. I was browsing through literature, and I ...
3
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1answer
96 views

What causes Copper Rose?

We made a solution of Tetrakis Copper(I) hexafluorophosphate and the usual color is yellowish. As it oxidizes to Cu(II), it should turn blue. However, our current mixture has an off color that is ...
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3answers
6k views

Why are some salt solutions coloured?

I notice that salt solutions of $\ce{NaCl}$ and $\ce{KCl}$ are colourless while those of $\ce{CuSO4}$ and $\ce{FeSO4}$ are coloured. I got as far as figuring that it has to do with the transition ...