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# Boiling Point Of A Liquid Under Vacuum

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### #1 sateeshkumar830

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Posted 04 April 2016 - 11:34 PM

Dear sir,

How to calculate boiling point of chemical with respective Vacuume. i know the boiling point of one chemical at 5mmhg. how to calculate the boiling point at 760mmhg. i dont know the antonie constants of that chemical. For organic solvent we know the antonie constants , we can calculate by using antonie equation. how to calculate the boiling point of remaining chemical with respective vacuum.

### #2 shantanuk100

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Posted 05 April 2016 - 06:09 AM

Dear Sateesh,

1. You have a fluid whose Boiling point is known at 5mm Hg.

But without knowing which fluid it is, or atleast what kind of phase diagram it has, or atleast it's antoine constants, I would say it is impossible to guess the Boiling point.

2. The best you can do is to calculate it from the antoine equation constants but you say that you do not know the values of the constants.

So it is difficult since different kinds of phase changes are possible.

Is there any other data given ?

3. If you know antoine equation constants, then please use the spreadsheet below that I've made and used earlier.

It needs input of your local conditions and the antoine equations for vapor pressure calculations.

4. The boiling point will then be the temperature at which your saturated vapor pressure is equal to the local atmospheric pressure.

Regards,

Shantanu Kallakuri

#### Attached Files

Edited by shantanuk100, 05 April 2016 - 06:10 AM.

### #3 Profe

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Posted 06 April 2016 - 09:26 AM

Hi Sateesh

Attached is an Excel file used for Petroleun fractions to transform ASTM D1160 distillation at low pressure (1-50 mmHg) to atmospheric pressure D1160. I think this may be helpful.

Ref: Ref: Petroleum refining - vol 1 - crude oil - petroleum products - process flowsheets - Technip J. P. Wauquier p 102

Note: Use your know data Boiling point at 5 mmHg to 50 % vol.

Good luck

Fausto.

#### Attached Files

Edited by Profe, 06 April 2016 - 09:38 AM.

### #4 breizh

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Posted 06 April 2016 - 07:53 PM

Hi Sateesh ,

The best way is to perform the experimentation with an approved lab , familiar with such work . You have not been generous about the chemicals , difficult to help more .

Breizh

### #5 Napo

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Posted 06 April 2016 - 09:02 PM

Sateesh,

What is the boiling point of your chemical at 5 mm Hg?.

Maybe you can do an estimation by means a vapour pressure nomograms, for example.

Napo.

### #6 P.K.Rao

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Posted 06 April 2016 - 10:53 PM

Please refer to ASM D 1160. Section 7.3.

### #7 breizh

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Posted 07 April 2016 - 08:24 PM

Hi ,

Will it help?

http://www.sigmaaldr...omo-assets.html

Breizh

### #8 MrShorty

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Posted 11 April 2016 - 10:45 AM

A little late to this discussion, but I would add a couple of thoughts.

1) How accurate do you need the normal boiling point? There is no question that, when accuracy is important, one needs laboratory measurements to get an accurate vapor pressure vs. temperature curve. If accuracy is less important, then there are some different means of estimating vapor pressure vs. temperature.

2) Estimation techniques that I am aware of are almost all based on the principle of corresponding states. If you are unfamiliar with the principle of corresponding states, put it to your favorite internet search engine or wikipedia or look it up in a good textbook. One equation that I am familiar with is the Riedel equation ln(p)=A+B/T+Cln(T)+DT^6. When temperature and pressure are expressed on a reduced basis, the four parameters of the Riedel equation can be expressed in terms of a single parameter. If you can estimate a critical temperature and pressure, then you can derive the rest of the vapor pressure curve. The accuracy of this technique, of course, depends greatly on the accuracy of the estimation of the critical properties.

3) Do you have access to the textbook The Properties of Gases and Liquids? This is a good text used by many engineers as a reference for estimation techniques for many different properties. This text describes Riedel's equation, along with some other techniques for estimating vapor pressures.

Edited by MrShorty, 11 April 2016 - 10:46 AM.

### #9 shantanuk100

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Posted 11 April 2016 - 05:55 PM

@ Mr.Shorty

But I don't think it is possible to estimate the Critical points without knowing what substance it is.

Regards,

Shantanu

### #10 MrShorty

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Posted 12 April 2016 - 11:58 AM

@shantanu

True enough. Did the OP say that he has no idea what the compound in question is, or did he merely not tell us what it is? If he knows what it is, but chose not to reveal the compound's identity in an open forum, then he should be able to use that information to find critical constants. If he truly does not know anything about the compound (molecular formula, structure, name, or anything like that), then he will have real difficulty estimating critical constants.

I have heard of, though never used, a method described by Gunn and Yamada that uses a few vapor pressure points and a few density points to estimate critical properties without knowing atomic or molecular structure. It still requires more information than the OP says he has, though.

I guess it really boils down to whether the OP has really divulged "everything" he knows about this compound, or if he has some information not divulged.

### #11 shantanuk100

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Posted 13 April 2016 - 12:00 AM

@ Mr.Shorty,

Hmm.. That's true.

As long as the OP knows the substance there should not be a problem.

The OP has only said they dont know the antoine constant, so I guess there's more clarity needed on that.

Regards,

Shantanu

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Posted 13 April 2016 - 12:03 AM

Dear sir,

How to calculate boiling point of chemical with respective Vacuume. i know the boiling point of one chemical at 5mmhg. how to calculate the boiling point at 760mmhg. i dont know the antonie constants of that chemical. For organic solvent we know the antonie constants , we can calculate by using antonie equation. how to calculate the boiling point of remaining chemical with respective vacuum.

Hi,

It's really difficult unless you have few other datapoints to regress the coeffiecient. What's this fluid?