DubaiAmateurRocketry
National Hazard
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 841
Registered: 10-5-2013
Location: LA, CA, USA
Member Is Offline
Mood: In research
|
|
temperature dependent color change of a solution?
Anyone aware of color change of solutions where the color change starts at around a temperature of 40 celsius ?
|
|
Sulaiman
International Hazard
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 3631
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
for many of the thermochromic pigments available via eBay,
31oC is a common transition temperature
some transition at 13oC
I've not noticed any at 40oC.
Most of the "thermometer strip" via eBay have one 40oC patch.
(I was looking for a thermochromic dye to use in my recirculating water-cooled condenser system
but only found insoluble pigments that I thought could cause blockages,
while searching I did come across a pigment manufacturer with a range of transition temperatures,
too expensive for me so I did not keep a link )
[Edited on 7-10-2018 by Sulaiman]
|
|
fusso
International Hazard
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 1922
Registered: 23-6-2017
Location: 4 ∥ universes ahead of you
Member Is Offline
|
|
Can adjusting cobalt & chloride concentration change the transition temp?
|
|
DubaiAmateurRocketry
National Hazard
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 841
Registered: 10-5-2013
Location: LA, CA, USA
Member Is Offline
Mood: In research
|
|
Sulaiman, theyre not in solutions though? do they still behave the same in a solution ?
|
|
Sulaiman
International Hazard
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 3631
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
I'm not sure but it seems that the pigments are insoluble in anything that does not destroy the thermochromic effect,
so the pigment is used like those in oil paints, lacquers etc. a slurry/colloid/suspension or embedded in a polymer.
I think.
|
|
DraconicAcid
International Hazard
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 4298
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline
Mood: Semi-victorious.
|
|
Cobalt chloride in solution will change colour with temperature. You could probably play with the concentrations of cobalt and chloride ion so that
40 oC is your transition point. Not sure how broad of a range it will change over, though.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
|
|
Sulaiman
International Hazard
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 3631
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
I believe that the thermochromic change in cobalt chloride is practically irreversible ?
|
|
woelen
Super Administrator
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 7988
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
A pinch of cobaltous chloride or cobaltous sulfate, dissolved in 10 ml of appr. 3 M HCl makes a good temperature dependent solution. You need to
carefully prepare the solution. Dissolve some of the cobalt salt in cold 5M HCl. You get a purple/blueish solution. Drip in cold water while swirling,
until the liquid becomes purely pink. At that point the acid will be around 3M.
If you heat this pink solution then you can get it dark royal blue when it is hot and it is pink when it is at room temperature again. This effect is
100% reversible as often as you want. I put some of this solution in a glass ampoule and use it for demo purposes. I just put the ampoule with pink
liquid in a cup of hot water (e.g. from a coffee machine) such that the top half of the ampoule remains above the hot water so that you can handle it
without hurting your hand. The effect is really striking. I think that the transition occurs over a range of appr. 30 C (purely pink) to 70 C (deep
royal blue).
|
|