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General Science => General Science => Topic started by: scientizscht on 15/08/2019 19:08:37

Title: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: scientizscht on 15/08/2019 19:08:37
Hello!

I want to calculate how much the liquid level will rise in a capillary of 0.26mm diameter.

Any idea?

Thanks!
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: Bored chemist on 15/08/2019 19:37:16
Did you try this?
https://en.wikipedia.org/wiki/Capillary_action#Height_of_a_meniscus
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: scientizscht on 15/08/2019 23:07:26
Did you try this?
https://en.wikipedia.org/wiki/Capillary_action#Height_of_a_meniscus

Yes, I have a problem with the contact angle, how can I determine it?
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: alancalverd on 16/08/2019 07:34:11
That's a whole can of worms, because it is extremely sensitive to surface contamination, temperature, pressure, history, and just about every physical and chemical variable you can think of. It can even be negative (mercury in glass is a common example).

The general approach is to build your system and use the measured capillary rise to estimate contact angle!
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: Bored chemist on 17/08/2019 12:31:51
https://en.wikipedia.org/wiki/Contact_angle#Measuring_methods

Though I agree with Alan, the easiest thing to do is measure the capillary rise.
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: scientizscht on 17/08/2019 16:20:14
What is the real cause of capillary rise?

Is it the attractive forces between the liquid and the walls of the capillary?

Is it the attractive forces between the molecules of the liquid?

Is it the atmospheric pressure?
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: Bored chemist on 17/08/2019 17:18:02
What is the real cause of capillary rise?

Is it the attractive forces between the liquid and the walls of the capillary?

Is it the attractive forces between the molecules of the liquid?

Is it the atmospheric pressure?
Which factors appear in the equation for calculating it?
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: scientizscht on 20/08/2019 21:07:49
What is the real cause of capillary rise?

Is it the attractive forces between the liquid and the walls of the capillary?

Is it the attractive forces between the molecules of the liquid?

Is it the atmospheric pressure?
Which factors appear in the equation for calculating it?

Many that I don't know what they depend on, e.g. the contact angle or the surface tension.

Any specific answer?
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: Bored chemist on 20/08/2019 21:13:41
Of the precisely three things listed;
Is it the attractive forces between the liquid and the walls of the capillary?

Is it the attractive forces between the molecules of the liquid?

Is it the atmospheric pressure?
Which factors appear in the equation for calculating it?
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: scientizscht on 20/08/2019 22:17:28
Of the precisely three things listed;
Is it the attractive forces between the liquid and the walls of the capillary?

Is it the attractive forces between the molecules of the liquid?

Is it the atmospheric pressure?
Which factors appear in the equation for calculating it?

I don't like quizzes, if you know the answer feel free to say it.
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: Bored chemist on 21/08/2019 07:33:34
You already know the answer.
Since the atmospheric pressure does not appear in the equation for calculating capillary rise, it can't cause it.

Why didn't you realise that?

Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: scientizscht on 21/08/2019 13:01:29
As I said before, in the equation there are contact angle and surface tension that I do not know their dependencies.
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: Bored chemist on 21/08/2019 19:59:12
As I said before, in the equation there are contact angle and surface tension that I do not know their dependencies.
And, as I said, the important thing is what is NOT in the equation.
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: scientizscht on 21/08/2019 22:38:44
As I said before, in the equation there are contact angle and surface tension that I do not know their dependencies.
And, as I said, the important thing is what is NOT in the equation.

What is that?
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: Bored chemist on 23/08/2019 13:17:32
As I said before, in the equation there are contact angle and surface tension that I do not know their dependencies.
And, as I said, the important thing is what is NOT in the equation.

What is that?


Since the atmospheric pressure does not appear in the equation...
Title: Re: How to calculate the height of a liquid in a capillary due to surface tension?
Post by: alancalverd on 23/08/2019 20:27:17
The answer is "pretty well everything except atmospheric pressure, unless the atmosphere contains gases that dissolve in or react with the liquid or the solid, which most probably do."