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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31k views

Difference between white sugar, brown sugar and red sugar

I always get confusing why the appearance of normal sugar (the white one), brown sugar and red sugar are different although they are sugar. Is it because they each have different molecular formulae or ...
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1answer
881 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 ...
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1answer
1k views

Why is ruthenium(III) intensely colored in water

I was preparing a solution of ruthenium(III) chloride (aqueous) when I added some (nearly black) $\ce{RuCl3 . H2O}$ to the water. I was surprised that a tiny amount could dye the water so well, I'd ...
4
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1answer
11k views

Predicting color of precipitate

Is there any way of predicting whether a precipitate will be colored? I know that for solutions, transition metal ions with unfilled d-orbitals will have color because of d-orbital splitting in the ...
4
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1answer
235 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 ...
4
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1answer
555 views

Aqua Regia Coloring

I was working with Aqua Regia in the lab today and was impressed by how quickly the solution (HCl and HNO3) changed colors from a colorless liquid to orange to a deep red. I didn't time it, but I ...
4
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1answer
706 views

Why do complex ions not emit light from de-excitations of electrons?

I understand that complex ions are coloured due to d-orbital splitting which results in electrons being able to absorb wavelengths of visible light and become excited to the higher energy state ...
4
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1answer
1k views

Colored Flames Experiment

I am going to be doing a gender reveal for my sister's pregnancy. To do this, we wanted to light a huge fire pit and throw in a chemical to change the fire into the color (red/pink for girl, blue/...
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2answers
530 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?)
4
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1answer
295 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 ...
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0answers
1k views

Mechanism of DPD (N,N-diethyl-p-phenylenediamine) reaction with free chlorine

NOTE: As I've been finding new informations about the question, I've been editing the question to keep it up to date. If some comment doesn't make sense just check the Edit History. DPD (N,N-diethyl-...
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364 views

Why is nitrogen dioxide brown?

Nitrogen dioxide (NO2) is a reddish brown molecule, while its dimer nitrogen tetroxide (N2O4) is colorless. Can you give a reasonably detailed explanation for this from electronic structure theory? ...
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275 views

Why do isomeric complexes often have different colors? [duplicate]

For example, $\ce{[Cr(NH3)2Cl2]+}$ One isomer is green and the other is violet. Why is this so? The ligands are the same, the oxidation state is the same, and so is the coordination number. The only ...
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195 views

Why does the electrolyte used in Lechlanché cell turn blue?

In my school there are jars which are turned into Lechlanché cells. Basically the cell has aqueous ammonium chloride solution as the electrolyte which is obviously transparent in the beginning. The ...
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0answers
3k views

Why is the geometry of [Ni(CN)4)]2- square planar? Why is it colorless?

Why is the geometry of $\ce{[Ni(CN)4)]^{2-}}$ square planar given that it has a coordination number of 4? Shouldn't its geometry be tetrahedral as it would minimise the bond angle and hence repulsion?...
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176 views

Can pure elements have different colors?

This question was inspired by this: Are there colorful metals besides gold and copper? I was wondering how the color of a pure element could be changed. I know that it is possible for color to change ...
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2answers
1k views

How is Persian blue rock salt made?

How is Persian blue rock salt made and what does it contain that makes it look blue?
3
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2answers
190 views

Is there a way to create natural Red food coloring from Turmeric in the house kitchen?

As a non chemist I have read in the Wikipedia article Curcumin that: Curcumin becomes bright red when it interacts electrostatically with phospholipid film. This text appeared without source ...
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2answers
3k views

Why is a [Cu(SCN)2] complex black?

I've been creating various Copper(II) complexes using different ligands and predicting their relative hues using Crystal Field Theory by using the spectrochemical series to predict the extent of d ...
3
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1answer
213 views

Why are most glow-in-the-dark things green?

I've noticed that many glow-in-the-dark objects you can purchase in the store are green. Occasionally I would come across something that was orange or blue, but mostly it seems that green is the ...
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57 views

How do you track Iodine on a black surface?

While spraying with starch solution seems to be standard procedure, blue-black colouring seems not to stand out from a black (charcoal) surface.
3
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1answer
1k views

Color imparted to flame and color of coordination compounds

When we heat a ionic substance/compound, the ionic bond gets weakened and the metal is ionized. Is the color imparted to the flame due to absorption of light? i.e. Do we see the remaining wavelengths? ...
3
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1answer
6k views

Why do elements change their colour in reactions?

We are almost common with the reaction: $\mathrm {CuSO_4+Fe = FeSO_4+Cu }$. In this reaction initially Copper sulphate is bluish in colour, which gradually changes to pale green. I want to know, why ...
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2answers
1k 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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1answer
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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? ...
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3answers
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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
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Why does molten salt turn black?

Lately I have been seeing quite a few videos on YouTube about molten salt, specifically table salt (NaCl). One of the things that interests me about it is that regardless of what melting technique or ...
3
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1answer
6k views

Why is MnSO4 colourless?

I get it that transition metal salts have colour due to d-d transition from $\mathrm{t_{2g}}$ to $\mathrm{e_g}$ orbitals in octahedral and the opposite in tetrahedral but why would $\ce{Mn^2+}$ not ...
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1answer
4k views

Bleach turned towel bright pink before fading to white

We have some relatively new white towels that were getting dirty, so we decided to clean them with bleach (standard Clorox). When we sprayed the diluted bleach on the towels they immediately turned ...
3
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1answer
97 views

Color difference among oxovanadium species

Why dioxovanadium $\ce{[VO2]+}$ is pale yellow, whereas orthovanadate $\ce{[VO4]^3-}$ is colorless? Both of them should be colorless if we ignore charge transfer for a moment, because in both cases ...
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1answer
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Clarification on absorption spectra and crystal field theory

My textbook, Chemistry: The Central Science, gives this figure to explain the purple color of the hexaaquatitanium(III) ion: Such absorption spectra are common to chemistry and biochemistry. However, ...
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1answer
1k views

How does complex ion differ from ligand complex?

As I understand, in terms of "colouring", ligand complex cause a transition metal cation centre's d-shell to split, allowing the electrons in that region to absorb specific frequencies of light, and ...
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1answer
1k 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 ...
3
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1answer
209 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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1answer
3k views

Failed esterification of 1-butanol and ethanoic acid

I did an esterification experiment of 1-butanol and ethanoic acid. 30 mL of 1-butanol was added followed by 30 mL of ethanoic acid, and then 1.5 mL of concentrated sulphuric acid and some boiling ...
3
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2answers
328 views

Photosynthesis: Chlorophyll and color. [closed]

As I know, chlorophyll is green as it absorbs all wavelengths but green. It absorbs red, yellow, blue, purple, etc. Thus, the plant does not utilize green light. i] Why is chlorophyll green? Is ...
3
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1answer
403 views

Is there a way to make long delay ink?

I would like to make some invisible ink that apears by itself after some time, preferably at least a couple of days. I want to write a dedication in a book with it, so it would probably be fine if the ...
3
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1answer
611 views

50-90'C color changing chemical to use as warning marker for hot electronics?

I am testing electronics with many potentially unstable contacts, and I wish to monitor if they rise above 50 to 90 degrees Celsius, i.e. using carbon paper that would darken progressively from 50 to ...
3
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1answer
516 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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0answers
84 views

Dilute FeCl3 colour is darker at 5e-4M than at 5e-3M. Why?

I did two different dilutions of $\ce{FeCl3}$ (within a $\pu{1h}$ timespan) from $\pu{0.05 M}$, and the one with $\pu{5E-4 M}$ concentration looked a darker orange than the one with $\pu{5E-3 M}$. ...
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1answer
6k views

Explaining the colour change in the potassium permanganate titration of iron(II) ions

In the redox titration: $$\ce{MnO4- + 8 H+ + 5 Fe^2+ -> Mn^2+ + 4 H2O + 5 Fe^3+}$$ the colour change which occurs is purple to colourless, because of the decreased concentration of permanganate ...
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0answers
212 views

Explaining color differences using bond conjugation

I'd like to ask about how the color differences between the dyes methyl violet and malachite green can be explained. Looking at the conjugated bonds of each, methyl violet seems to be more conjugated ...
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0answers
217 views

Transition Metals that react with Vanillin and their Complexes [closed]

My question is simply whether anyone knows what are the transition metals that the phenol group of the vanillin molecule could react with, and thereby produce discolorations. This question is ...
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0answers
53 views

Color fading in contact with air over period of time [closed]

I am a product designer and I am wondering if there is a pigment or ink that is able to fade over time by staying in contact with air? I am designing a label that should change color after ...
3
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0answers
402 views

How do counter-ions influence the color of coordination compounds?

I've been asking myself for a while now how counter-ions sometimes change the colors of coordination compounds. Like when I use d-metals as counter-ions to precipitate Cyanoferrates. I looked at ...
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0answers
91 views

Colour change on exposure to singlet oxygen?

Is there a dye that is particularly well suited to radical colour change on interaction with singlet oxygen, preferably non-toxic? Based on this answer: https://chemistry.stackexchange.com/a/27633/...
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421 views

How does a photochemical reaction of lignin with oxygen (yellowing of paper) produce chromophores?

Edit: This question is about chromophore production in lignin as found in low cost or short-term use paper such as newsprint. A different, excellent answer describes oxidation yellowing of the ...
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0answers
46 views

Trouble understanding Bradford Assay

From what I understand, the Bradford reagent contains Coomassie Brilliant Blue in an acidic solution so both of the (sulfonic acid groups? I'm not sure if this is the correct name- I can't seem to ...
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0answers
911 views

How does the “methylamine test for sugars” work exactly?

There is a test that enables distinction of sugars between mono- and oligosachharides. It consists letting methylamine react with an aqueous solution of the sugar under alkalic conditions and ...
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4answers
124 views

Books showing colorful images of elementary particles…is this true? [closed]

Do electrons or protons or any other elementary particle have colors of their own or do they have smell?