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Colorimetry: Why use complementary colour?

OK so my colour-physics is not so good...

I need to know why we use the complementary colour to that of the solution being tested for colorimetry.

Also, are there any units of absorption?

Cheers. +rep as thanks! :smile:
I just set out to answer this and then realised i didnt really know the answer lol...

So you have a sample in a cuvette, white light is striking the sample and some of it being absorbed. The remaining frequencies are transmitted and are what gives the solution its colour. If a solution is blue, then it is absorbing orange light. By using an orange filter you're only letting orange light hit the sample... so perhaps the sensor sensitivity is somehow improved by only allowing frequencies which will show a level of absorption through. i.e. if all the frequencies(except orange) were hitting it it'd be harder to measure variations.

This is speculation :dontknow:
Using the filter which is a complementary colour to the solution being tested means the only colour of light being absorbed or transmitted by the solution is the one which is most strongly absorbed, making it easier to measure the concentration of the solution.
Reply 3
Avatar for Pigster
Pigster
20
Original post by sharpyt_14
Using the filter which is a complementary colour to the solution being tested means the only colour of light being absorbed or transmitted by the solution is the one which is most strongly absorbed, making it easier to measure the concentration of the solution.


Welcome to TSR.

Before replying to threads, it is worth checking how old they are.

This one was probably last visited when you were still in primary school. Your reply is pretty unlikely to be seen by anyone who was part of it.
Reply 4
Avatar for Awan0903
Awan0903
7
What colour of the calorimeter filter should be used when using a red coloured sample?
Please reply soon.
Original post by Awan0903
What colour of the calorimeter filter should be used when using a red coloured sample?
Please reply soon.



Reply 6
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Awan0903
7
Original post by charco

what is this??
Original post by Awan0903
what is this??


The complementary colour wheel.

Just go to the opposite side of the wheel to find the complementary colour.
What would happen if you used the same colour filter as your solution?
Reply 9
Avatar for eddiemason
eddiemason
1
Original post by Pigster
Welcome to TSR.

Before replying to threads, it is worth checking how old they are.

This one was probably last visited when you were still in primary school. Your reply is pretty unlikely to be seen by anyone who was part of it.


I saw it and found it helpful
(edited 7 months ago)
Original post by sharpyt_14
Using the filter which is a complementary colour to the solution being tested means the only colour of light being absorbed or transmitted by the solution is the one which is most strongly absorbed, making it easier to measure the concentration of the solution.


thanks that helped me understand, well explained
Hi @eddiemason,

I'm pleased to hear that you found this thread useful.

However, please be aware that it's 13 years old. We generally avoid reviving old threads, as there's a risk that queries may go unnoticed when threads are several years old and already have responses.

I will now close this thread, but don't hesitate to start a new thread if you have any additional questions.

Have a great weekend,

5hyl33n

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