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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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What is the source of the intense blue colour of ultramarine pigment?

The pigment ultramarine was once a rare, expensive and highly prized pigment for artists because of its intense, long lasting blue colour. It was one of the most expensive pigments used in renaissance ...
matt_black's user avatar
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2 votes
0 answers
22 views

Is there a cheaper alternative to Liquid Color Standards?

I'm trying to create a sensor that measures the fluid color within a PVC tube that exits from a patient's surgical wound. I have a handheld spectrophotometer and a TCS3200 sensor, and I'm trying to ...
Bilal Bahadır Akbulut's user avatar
-2 votes
2 answers
73 views

Azo dyes with different colours than Yellow, Orange and Red [closed]

Why are there just Azo dyes with colours of Yellow Orange and Red. Do the molecules become to be unstable with a greater pi-electron System? Every dye or indicator with other colours are'nt Azo dyes.
Jonah's user avatar
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0 answers
23 views

Are there any yellow ferrous (ideally stainless) alloys? Perhaps after heating?

I recently learned about purple gold, which is roughly 80%-20% Au - Al by weight. (It's beautiful.) I also know that Titanium will turn bright purple if heated sufficiently (probably an oxide layer). ...
L. Jones's user avatar
0 votes
0 answers
52 views

Extended resonance and colour [duplicate]

I was pretty sure that this would've been asked before but I couldn't find anything here. I've noticed that system with multiple benzene rings and pi donating/accepting groups tend to be quite ...
Gaurav Sai Maddipati's user avatar
0 votes
1 answer
42 views

Finding the pH level of a liquid process

A photo of 15ml of distilled water accompanied with 3 drops of both universal indicator and bromothymol blue were mixed together and taken (white background was put into the back of the beake). The ...
Jimmy Zeng's user avatar
-1 votes
1 answer
740 views

Are there pigments that will only show their colour after applying water? [closed]

I am looking for pigments that at first are not showing their colour (and appear colourless), but after adding water or another 'component' like oil/alcohol etc. will show their colour. My excuses for ...
Diorcula's user avatar
3 votes
0 answers
50 views

The colour of sunset yellow powder (red, orange, and yellow)

I asked about the colour of sunset yellow in water in the previous post (Changes of colour of sunset yellow in water). And here, I would like to raise another question based on sunset yellow. Sunset ...
Freeby Freeby's user avatar
2 votes
2 answers
496 views

Changes of colour of sunset yellow in water

I am conducting an experiment on “sunset yellow (FCF)”. Based on my observations, the substance, when in powder form, is bright red in colour (observed with naked eyes). When I dissolve the powder in ...
Freeby Freeby's user avatar
0 votes
0 answers
161 views

Products formed on reaction of aqueous solution of iron(III) nitrate nonahydrate

Crystalline iron(III) nitrate nonahydrate, Fe(NO3)3.9H2O, has a very pale violet color. When added to water, the crystals dissolve to form a brown solution. Treatment of this brown solution with ...
Priyanshu Kumar's user avatar
-2 votes
1 answer
143 views

Colour of coordination compounds due to d-d transition

Hexaaquanickel(II) is green but tetracyanidonickelate(II) is colourless. On internet I found two explanations. One used valence bond theory that claimed there is no excitation of electron in ...
Harjot Dhillon's user avatar
0 votes
1 answer
70 views

Why Green Solution After Putting Bismuth Antimony in Nitrogen Acid

I am in a physics lab studying dislocation, and we submerged a bismuth antimony sample in nitrogen acid (about 50% concentration, if I remembered it right) as the first step to etch it. There were ...
Yuting Z's user avatar
0 votes
0 answers
30 views

Silica gel reheating (orange)

I am a non-chemist looking for some advice! I am an archaeologist and am currently using moisture-indicating silica gel (orange) to dry out some metal finds from our excavations. I have reheated ...
Michael Ann Bevivino's user avatar
1 vote
0 answers
153 views

Color of coordination compounds

My book(Page $259$ section $9.5.5$) says that the color mainly comes from absorption of light in the coordination compound: The color is complementary of the wavelength it absorbs , the wavelength ...
Razz's user avatar
  • 137
5 votes
1 answer
317 views

Can a colorant be mixed into zirconia powder?

I’m wanting to color zirconium dioxide into beads after it is fired but I would like to get more colors than just white and the high temperature black oxide. Can I mix other metal oxides to zirconium ...
Cara Loibl's user avatar
-1 votes
1 answer
351 views

Reason behind paramagnetic substances having color

I've read in many books that paramagnetic substances are coloured while diamagnetic substances are colourless (yes there are some exceptions too). But nowhere i could find a reason for this phenomenon....
Gnanadeep Sai's user avatar
-1 votes
1 answer
71 views

What is that substance coming from tractor tire?

I have old tractor with Bridgestone tires. When I press a clean white tissue against the tire, a black spot show on the tissue. Is that substance carbon black and it’s harmful to soil?
MasterMind's user avatar
4 votes
2 answers
455 views

Why does color of substances not disappear after some time?

Some compounds are colored due to HOMO-LUMO transition. We see the complimentary color to the frequency which the electron absorbs to get the high molecular orbital. But after some the electron should ...
Garv Chaudha's user avatar
1 vote
1 answer
285 views

Why hot iron turns from red to white and then blue? [closed]

While reading structure of atom chapter no. 2 from ncert class 11th chemistry part 1 book, I got a doubt. In the book it says on page 40 that: Hot objects emit electromagnetic radiations over a wide ...
S K's user avatar
  • 33
-3 votes
1 answer
136 views

Colour of CuO and CuCl2 [closed]

Colour of $\ce{Cu^2+}$ is blue. Then why is the colour of $\ce{CuCl2}$ green and $\ce{CuO}$ black? Because both of these compounds have $\ce{Cu^2+}$.
Sarban Bhattacharya's user avatar
0 votes
0 answers
133 views

Color change when heating organic compound

I did just attend a lab class where I should synthesize 3,6-dibromo- N-propylcarbazole from N-propylcarbazole by bromination. Once, the bromination was over the color of the reaction content was ...
maniboy's user avatar
1 vote
0 answers
131 views

Resazurin not turning pink

I want to add resazurin to my media as an anaerobic indicator. To my understanding, the resazurin is blue when first added to the media, then turns pink after autoclaving, and finally it turns ...
David Madrigal Trejo's user avatar
3 votes
1 answer
272 views

Detection of Nitrogen and Sulfur in Lassaigne's Test

In Lassaigne's test for the detection of nitrogen and/or sulfur in organic compounds, we prepare Lassaigne's extract. In this extract, NaCN is formed if nitrogen is present, and $\ce{Na2S}$ is formed ...
R H's user avatar
  • 39
3 votes
0 answers
158 views

Colored inorganic liquids: why is SCl2 red, and S2Cl2 orange?

Those do not involve d orbitals, so there is no crystal field theory or ligand theory. Do we have a name of study that only involves p orbitals? Since I think molecular theory is for all s p d f ...
Neal Conroy's user avatar
4 votes
1 answer
1k views

Colour properties of nickel complexes

According to Crystal Field theory (CFT), complexes with stronger ligands must absorb light with higher frequency hence would transmit corresponding complementary colour. The colour of $(\ce{[Ni(H2O)2(...
Mithun M R's user avatar
6 votes
2 answers
3k views

Colour changing Lipstick

I have bought a colour changing lipstick with the colour Phloxine B.(Other ingredients, see below...) Normally this colour changes to pink at pH 5. So this means on skin it changes its colour because ...
Jean Claude Delaveine's user avatar
1 vote
0 answers
217 views

white vs light pink color of MgO

Recently I ordered some high purity MgO, which is light pink in color. However, the old powder I was using was white. MSDS also suggests that it should be white. Can anyone explain the reason of two ...
user49535's user avatar
  • 137
0 votes
0 answers
424 views

Why wavelength of Rubidium flame test(red violet) is more than Lithium(crimson red)

My teacher show this table from my book Here, you can see Red violet wavelength is more than Lithium, which is against order of visible light which increase according to acronym 'VIBGYOR' According ...
Shinnosuke's user avatar
6 votes
0 answers
98 views

Why sulfur dissolved in ethylenediamine turns green?

Davis, R. E., & Nakshbendi, H. F. (1962). Sulfur in Amine Solvents. Journal of the American Chemical Society, 84(11), 2085–2090. doi:10.1021/ja00870a017 I've also done this experiment. But what ...
seilgu's user avatar
  • 281
6 votes
1 answer
620 views

Why does benzaldehyde turn yellow?

We used benzaldehyde for a demonstration of the Cannizzaro reaction in school, but the liquid we used appeared visibly yellow, as opposed to the colourless liquid described by Wikipedia. A few reasons ...
Jono94's user avatar
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1 vote
0 answers
108 views

Could a beach have green or blue sand due to a nearby copper deposit? How poisonous would such a beach be? [closed]

I am in the midst of a world building project and am wondering about green sand from copper oxide/patina material. The material could either be washed into the water from a nearby land deposit or be ...
Lynx's user avatar
  • 19
-2 votes
1 answer
360 views

Why are iodine precipitates yellow? [closed]

Why do iodine precipitates appear yellow? Learning about precipitates I noticed that compounds like Lead Iodide and Silver Iodide are yellow.
hanning's user avatar
  • 17
2 votes
1 answer
354 views

Colour of ferrous hydroxide crystal

My chemistry teacher said that pure $\ce{Fe(OH)2}$ is a "white" crystalline solid in anaerobic environments, and acquires the usual green tinge, the colour of $\ce{Fe(II)}$, when in contact ...
Jono94's user avatar
  • 593
4 votes
1 answer
371 views

Intense purple colour of litmus paper in contact with calcium oxide

When conducting an experiment to identify some common chemicals, I tested crystal/powder samples of the chemicals with moist litmus paper. When I put a piece of blue paper on some $\ce{CaO}$ powder, ...
Jono94's user avatar
  • 593
3 votes
0 answers
79 views

Why is hexacyanoferrate(II) coloured whereas tetrachlorocadmiate(II) is not, even though both lack unpaired electrons?

$\ce{K4[Fe(CN)6]}$ is coloured whereas $\ce{Na2[CdCl4]}$ is not. Even Laporte selection rule would suggest the tetrahedral cadmium complex to have a higher intensity of colour than the octahedral iron ...
Confused's user avatar
10 votes
0 answers
151 views

Why are vapours of xenon hexafluoride coloured?

According to Wikipedia, [...] It is a colorless solid that readily sublimes into intensely yellow vapors. It is clear from the above statement that $\ce{XeF6}$ is colourless in solid form. But why ...
Infinite's user avatar
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1 vote
0 answers
44 views

Why do the links in a plastic chain become different colors?

I have a plastic chain, about 5 meters long, sitting between two wooden posts. The link has 1 meter long sections of alternating white/red links. It's been sitting there for 2 years, and the once red ...
Magnus's user avatar
  • 109
3 votes
1 answer
250 views

How does pressure affect the color of reaction medium with equimolar amounts or reactants and products at equilibrium?

Chlorine gas is pale yellow-green, and both hydrogen and hydrogen chloride are colorless gases. According to the Le Chatelier's principle, the change in pressure will not affect the following ...
nitsir's user avatar
  • 41
1 vote
0 answers
440 views

Why is AgOH brown when silver(I) ions are colorless?

As Wikipedia states, $\ce{Ag+}$ ions are colorless in solution: https://en.wikipedia.org/wiki/Color_of_chemicals Compounds that I know of containing $\ce{OH-}$ are also colorless or white (such as $\...
ernogal's user avatar
  • 37
2 votes
1 answer
406 views

Does nitrous oxide decolorize potassium permanganate?

My teacher says that nitrous oxide can't form any complex with manganese in aqueous solution, so it can't be oxidised. However, shouldn't it get oxidised as it is present in the intermediate oxidation ...
Priyansh Kumar's user avatar
0 votes
1 answer
394 views

How can I produce Red Iron oxide with electrolysis

I am producing Iron Oxide with the intention of using it for pigmentation. My attempts so far have been to use electrolysis. My first attempt I used Borax as an electrolyte and a 12 volt adapter with ...
Riley Hughes's user avatar
4 votes
0 answers
193 views

Ferrocene's band gap is supposed to make it colorless but it isn't. Why is it so?

Wang and Islam [1] state that the ferrocene molecule's band gap, i.e. the HOMO-LUMO gap at the Kohn-Sham level, is 5.03 eV, which corresponds to an absorption wavelength of at most 240 nm. So, ...
Kanghun Kim's user avatar
6 votes
2 answers
881 views

PVP-iodine and octenidine can stain skin purple, does the reaction create iodine radicals?

In this paper it is mentioned that ... octenidine can release iodine radicals from the PVP complex, resulting in a tissue irritation as well as strong brown to violet discolouration in the border ...
Michael Paul's user avatar
7 votes
2 answers
1k views

Why is NMP developing a yellow color after distillation?

I got an aqueous mother liquor of N-methyl-2-pyrrolidone (NMP) from some reaction I was running and when I redistilled it under vacuum, it came out colorless but turned yellow the next day. I am ...
Pulkit Sharma's user avatar
3 votes
1 answer
494 views

Colour of diamagnetic compounds using Crystal Field Theory

I know that the colour in coordination compounds can be explained by CFT in terms of d-d transitions. Are d-d transitions possible in diamagnetic complexes? Why does $\ce{[Co(NH3)6]^3+}$ show colour? ...
Aja's user avatar
  • 96
1 vote
1 answer
258 views

Why is instant coffee powder not as dark as the coffee resulting from it?

Instant coffee granules generally are of a light brown colour, while coffee made from it is a deep black. Pigments are far more concentrated in the dry form, to add water is to dilute them. Still, ...
HannesH's user avatar
  • 483
0 votes
1 answer
48 views

Simple bistable and reversible electrochromic reaction in solution

I'm not a chemist and I'm looking for a simple bistable and reversible electrochemical reaction that changes color, specifically: A liquid in a glass with two electrodes that when a voltage is ...
Marcos's user avatar
  • 11
5 votes
1 answer
961 views

Reaction between anilinium chloride with ferric chloride

I have a question about reaction between aniline and $\ce{FeCl3}$. I supposed that the following reaction proceeds with formation of brown precipitate: $$\ce{3C6H5NH2 + FeCl3 + 3H2O -> \underset{...
Ann Ivanov's user avatar
7 votes
4 answers
617 views

When pigments absorb light only around a single particular wavelength, why aren't they still white?

I'm trying to understand how organic molecules get their colour. One major factor are conjugated double bonds which create delocalized pi-orbitals (e.g. https://en.wikipedia.org/wiki/...
Bernhard Werner's user avatar
3 votes
0 answers
146 views

Briggs-Rauscher reaction doesn't oscillate and turns blue with Vitamin C

I tried to recreate the Briggs-Rauscher reaction by using a solution of $\ce{H2O2}$, $\ce{KIO3}$, $\ce{H2SO4}$, $\ce{CH2(COOH)2}$, $\ce{MnSO4}$ and a soluble starch. I used this recipe. In container ...
mathbunny's user avatar

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