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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3
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3answers
58 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.
8
votes
1answer
872 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
45 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 ...
3
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0answers
53 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
votes
1answer
65 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 ...
0
votes
1answer
24 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 ...
1
vote
1answer
780 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?
0
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0answers
32 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 ...
1
vote
1answer
40 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
votes
1answer
39 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
votes
1answer
41 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 ...
0
votes
2answers
63 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
votes
1answer
51 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 ...
0
votes
1answer
78 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?
1
vote
1answer
321 views
2
votes
3answers
682 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?
1
vote
3answers
140 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 ...
3
votes
3answers
159 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.
4
votes
1answer
293 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 ...
1
vote
0answers
78 views

What reaction took place?

Okay, so I was fiddling about in the chemistry lab, and I added: Sodium Nitroprusside (soln) $\small\ce{ Na_2[Fe(CN)_5NO] }$ with Potassium Ferrocyanide (soln) $\small\ce{ K_4[Fe(CN)_6] }$. ...
4
votes
3answers
135 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 ...
1
vote
2answers
132 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 ...
1
vote
1answer
147 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 ...
10
votes
3answers
7k 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?
4
votes
1answer
94 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
votes
1answer
95 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 ...
12
votes
2answers
5k 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 ...
5
votes
2answers
277 views

What chemical compounds were used in CRT phosphors?

In the old days computer monitors and televisions were built from cathode ray tubes (CRTs) where the image was generated by an electron beam hitting phosphors which emitted light approximating the ...
8
votes
1answer
109 views

Why do some materials turn black and others white after combustion?

Most solids objects turn black after they are burnt. But some turn white. Why is that ?
14
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3answers
1k views

How may copper acetate ligands be manipulated to change colors?

I have a solution of copper acetate and I would like to play around with the ligands to get different colors. Background: The copper acetate was made through mixing vinegar (5% acetic acid), NaCl, ...
9
votes
2answers
806 views

Color of chromate and permanganate

I've heard quite a few times that the chromate and permanganate have a $d^3s$ configuration. Also, their colors arise due to a rapid switching of electrons between the oxygen and metal atoms. I don't ...