recalculation of boiling points under vacuum

[cavos]

Hi!
Finally I buyed a vigreux column and a waterpump for vaccum fractional distillation enterpreise.
Ceylon nutmeg oil, anethum sowa seed oil,calmus and sassafrass are on the road. I got only a few question.
with my lowbudget glads and pump I bring the water to boil at 25-30 C. Vogel reference says that´s the like as 28 mmHg.
could someone good old bee tell how have I to calculate the Bp of this oils at this pressure point or to point me to a reference tbel? Any good suggest?

[acid_egg]

https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/nomograph.html

There is also a very good post by chromic(I think...?) giving the BP of safrole over a range of pressures...so UTFSE.

ps you might want to rethink how you title your posts

[cavos]

Thanks,
You might want to reth..

whiy?

[Rhodium]

Because your post is only about recalculation of boiling points under vacuum. Even if you intend to use the info to calculate the bp of certain essential oils, that is completely errelevant to the question, and thus it is counterproductive to list them in the title.

Also, the abbreviations you use doesn't look good, and they are not by any means standardized.

[cavos]

Allright! Looks now as a newbee usefull question!
After my re-calculation also the right answer to my qstions are:
If water boils at 30 C
safole: ~130
myristicine: ~165
dilapiole: ~173
right?

[technology]

If you look at the link provided it will give you the directions of how to workout the temp changes will be under reduced pressure.. however, the result in calculation is merely an ~approx however, it is a good ~approx so then you can get a good idea of what temp the fraction that you are collecting comes over.

read the calc chart and it should answer your question.

[cavos]

If I follow Rhodium writeup
Water 30 C = 60 Torr
Vogel says water 30 C = 30 torr
30 torr difference are like ~29 C.
do I something wrong?

[technology]

Do exactly what the chart sez.. and will find youre own answer: In this example, we assume that your vacuum source pulls 20 mmHg (20 torr), and that you want to determine the boiling point of water at that vacuum. The boiling point of water at normal pressure is 100°C. With the aid of a ruler, draw a line from 20 mmHg in the pressure graph (to the right), through 100°C in the middle graph ("boiling point corrected to 760 torr", this is the normal atmospherical pressure), and where this line intersects the line to the left ("Observed boiling point"), take your reading. About 15°C, right? This means that at a vacuum of 20 mmHg, water will boil already at 15°C, below normal room temperature. Compliments of Rhodium:-

https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/nomograph.html

For example if you want to distill your oil under reduced pressure. Safrole has a Bp of ~235 rnd abouts" correct me if wrong, but you can not heat the oil to that temp otherwise it will decompose (which you prob are aware of)so therefore, it is done under reduced pressure. So this is how its done: Work out what pressure you can reduce to, lets say 20mmHg Torr which is the column on the right, then you draw a line from 20mmHg Torr to the middle which is ~235'C (so you have a line gong from right to left thus far, which ends up on the left side which is ~120. So all you do is work on the same principle for other reduced pressure distillations. Water. say we will reduce the pressure to 60mmHg and we know the Bp is 100'C, so we draw a line from 60mmHg on the right through the middle to 100'C and arrive at the destination on the left which is ~ 30'C. So that answer your question about Rhodium and Vogel, Rhodium is correct and Vogel made a type error, shame on Vogel"

If this does not help, you are in the wrong field of interest, i dont no what else to say, but that hope this helps a bee or two.

Also as rhodium also states that this is an ~approx but however a good one, give or take a little. But atleast you have a ruff idea as to when it will come over.."

[cavos]

dear Technology,
I´am Newbee. I read and learn since a Year in this Forum.
I take suggest from this forum.One suggest ist :
Read the fucked vogel and learn.
I did it.
Now my mission is to learn how to perform a Fractional distillation under vacuum. I buy a pump, I utfse, I read I
know my pump can bring water to boil at 30 C and that Is alla I know. I utfs, I read and I ask to findout how many vacuum that Is. I compare the monograph with rhodium and I see a dgreat difference also I ask why.
Also it was very appreciable If you had to say to me simply,
"Cavos in the vogel there is a write error", whitout the rest that is for me to read like a Torquemada Faith defense a act.Do you know torquemada?

[acid_egg]

They say nature abhors a vacuum...in that case cavos do you have to sleep with rubber stoppers in your ears?.. ..only joking!

If your pump boils water at 30C then the pressure in the setup is about 30mmHg. This concurs with the nomograph reading when I use it. Read this for safrole in particular

https://www.thevespiary.org/rhodium/Rhodium/chemistry/safrole.distillation.html

and learn to use the nomograph for other distillations.

To my knowledge sass can be distilled at atmospheric pressure without much degradation. The 'typo' in Vogel is in fact correct.

[cavos]

thanks,
this was for me a goog one info.

[Rhodium]

That is because water is one of those liquids which gives the most aberrant results on a nomograph due to its very strong hydrogen bonds and thus high heat of vaporization. Try it on a less polar solvent (anything except small molecules with an OH group), and you will get better results.

I really should change my nomograph example to use another liquid than water, I'll put that on my to-do-list.

In the meantime, check Zubrick's full discussion about Nomograph usage in

Chapter 20 of "The Organic Chem Lab Survival Manual"

(https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/distillation4dummies.html)

[Mountain_Girl]

At

http://www.cheresources.com/iapwsif97.shtml

you can download an Excel add-in (Water97_v12.xla) which allows easy calculation of the properties of water and steam at various temps and pressures.

For example, the vapour pressure at temperature T will be calculated with the following function:

     pSatW(T)

T = temperature in °K

eg. vapor pressure of water at 100 °C,
the formula in worksheet cell is    

   =pSatW(373.15)

This will give the vapour press in bar which can be easily converted to mm Hg by changing the formula to:
 
=pSatW(373.15)*760/1.01325

[cavos]

Dear Rhodium ,
your Zubrick  doument is really the best document for newbee I ever seen! I think I will buy a copy of this book because the Vogel is sometimes to "Scholastic" and without a Teacher make the reading sometimes no sense.Properties of Water & Steam in Excel is realy interesting too, thanks Mountain_Girl!

[Rhodium]

cavos: Great, you gave me an idea - I'll include a direct link to the page on

http://www.amazon.com

where the book is sold, and by the increase in sales the author will get from that link can probably make up for the copyright crime I committed by putting a chapter of his book online. What's in the document at the moment is only the first two parts (of four), as I have not yet scanned the sections on Fractional Distillation and Steam Distillation techniques.

[methyl_ethyl]

Good Idea, this really is must have literature for the newbee.  And I am sure Zubrick, will drop all pending lawsuits against you.........