Dark Coloured Bottles in Chemistry Labs

  • Context: Undergrad 
  • Thread starter Thread starter Bubonic Plague
  • Start date Start date
  • Tags Tags
    Chemistry Labs
Click For Summary

Discussion Overview

The discussion revolves around the use of dark-colored bottles in chemistry labs, specifically addressing the reasons for their coloration and its effects on chemical stability. Participants explore the implications of light exposure on chemical reactions, the mechanisms by which light may cause decomposition, and the effectiveness of dark bottles in mitigating these effects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the effectiveness of dark bottles, suggesting that since dark colors absorb light, the energy may still be transferred to the chemicals, potentially leading to decomposition.
  • Another participant explains that visible light can cause chemical decomposition, while dark bottles convert light to heat, which does not cause decomposition.
  • Some participants express skepticism about the necessity of dark bottles, questioning why opaque or black bottles are not more commonly used if light exposure is a concern.
  • A participant mentions that hydrogen peroxide is stored in dark bottles to prevent photolysis, indicating a specific example of light-sensitive chemicals.
  • There is a discussion about the historical use of brown beer bottles to limit light exposure, with questions about the relationship between light and fermentation processes.
  • Participants inquire about the specific properties of light that enable it to decompose chemicals, contrasting it with heat energy.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness and necessity of dark bottles, with some supporting the idea that they prevent decomposition while others remain skeptical. The discussion includes multiple competing perspectives and remains unresolved regarding the best practices for storing light-sensitive chemicals.

Contextual Notes

Some claims about the mechanisms of light-induced decomposition and the properties of energy transfer remain unverified, and assumptions about the effectiveness of different bottle colors are not fully explored.

Who May Find This Useful

Individuals interested in chemistry, particularly those studying chemical stability and storage methods, may find this discussion relevant.

Bubonic Plague
Messages
94
Reaction score
0
When you enter a chemistry lab, on the bench, there are some bottles containing chemicals, and some of these chemical bottles are tinted so that they have a dark brownish colour.

My chemistry teacher had told the class that the dark colour is used to prevent light from getting to the chemicals stored in the bottle, so that the chemicals will last longer. But I don't understand why.

Let's say the bottle is not tinted and clear, the light will get to the chemicals, which is common sense, and provide energy for the chemicals to decompose or react.

Now let's say the bottle is tinted, the most of the light that falls on the bottle will be absorbed by the bottle, 'cause dark colours absorb more light. And the energy absorbed from the light will then be transferred by conduction to the chemicals, cause there will be a energy gradient between the chemical and the bottle. So in the end, it's all back to square one. So how does making the bottle dark in colour actually help in anyway?

My physics is not the greatest, please point out any flaws in my physics.:smile:
 
Physics news on Phys.org
In such cases, visible light (read: relatively high frequency light) is capable of making the chemical decompose. When the bottle is darkened, the light is converted to heat when it strikes the bottle. Heat, unlike light, does not cause the chemical to decompose.

It is true, however, that the bottle's walls reradiate the energy into the chemical, but mostly in the infrared spectrum (since all objects at room temperature radiate mostly in the infrared). The infrared photons do not have enough energy to activate the reaction, so the chemical stays fresh.

- Warren
 
chroot, your explanation is IMO correct. Still I suspect this might be an urban legend... If they are so concerned about light, why not paint the bottles black? And why are there no dark plastic bottles, just white ones (AFAIK)?
 
You may be familiar with hydrogen peroxide from the apothecary, stored in dark plastic bottles to prevent photolysis.
 
Originally posted by arcnets
chroot, your explanation is IMO correct. Still I suspect this might be an urban legend... If they are so concerned about light, why not paint the bottles black? And why are there no dark plastic bottles, just white ones (AFAIK)?

Opaque bottles would certainly keep the light out, and sometimes that is done, with especially sensitive liquids. But then you can't tell just by looking what is the level of fluid in the bottle.

In the old days before it was pasteurized, beer came in brown bottles.

I believe specifically UV radiation is the culprit.
 
dont forget about beer bottles!
 
In such cases, visible light (read: relatively high frequency light) is capable of making the chemical decompose. When the bottle is darkened, the light is converted to heat when it strikes the bottle. Heat, unlike light, does not cause the chemical to decompose.

What is that special property which light has that can decompose chemicals?

It is true, however, that the bottle's walls reradiate the energy into the chemical, but mostly in the infrared spectrum (since all objects at room temperature radiate mostly in the infrared). The infrared photons do not have enough energy to activate the reaction, so the chemical stays fresh.

What about through conduction too?
 
What is that special property which light has that can decompose chemicals?

the ability to carry energy?

in paticular, it carries the proper activation energy
 
Originally posted by selfAdjoint
In the old days before it was pasteurized, beer came in brown bottles.

So they didn't want to let light into prevent the beer from ... fermenting? what?

is fermenting what makes beer bad so that they would want to limit fermentation?

(note: I am not old enough for beer so i wouldn't really know too much about it)

can you briefly explain how pasteurizing does the same thing to beer as preventing light from entering the beer? i mean, what's the point of keeping the light out of the beer?
 
  • #10
Bubonic Plague
What is that special property which light has that can decompose chemicals?
As I mentioned above, photolysis[b(].
 
  • #11
the ability to carry energy?
As I mentioned above, photolysis.
Heat, unlike light, does not cause the chemical to decompose.
I know that light carries with it energy, but what is so different about the energy from light and the energy from heat which is conducted or radiated to the chemical that only energy from light can cause the chemicals to decompose?

Pardon me, i just can't seem to "see" the answer.
 

Similar threads

Undergrad Why does the effect linger with Glow in the dark?
  • · Replies 16 ·
Replies
16
Views
6K
Undergrad The physics behind mixing coloured pigments (questions inside post)
  • · Replies 4 ·
Replies
4
Views
3K
Why do we store open bottles of hydrogen mouth down?
  • · Replies 3 ·
Replies
3
Views
3K
Undergrad How does our brain differentiate between a source of light and a painted circle?
  • · Replies 9 ·
Replies
9
Views
2K
Undergrad Mysterious Flashes of Light in Dark Room
  • · Replies 7 ·
Replies
7
Views
15K
Implementing “Ab initio” approach in molecular mechanics method
  • · Replies 4 ·
Replies
4
Views
3K
Undergrad Where does the energy go if I raise and lower a block?
  • · Replies 6 ·
Replies
6
Views
3K
Turning oxygen into fluorine in our atmosphere
  • · Replies 5 ·
Replies
5
Views
3K
Undergrad Condenser lens retrofit for a lighting application
  • · Replies 24 ·
Replies
24
Views
4K
Admissions DOE SULI Advice For Biology Background - Renewable Energy Development
  • · Replies 1 ·
Replies
1
Views
2K