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Science Forum Index » Chemistry Forum » Thiele tube
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| Author |
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| Allan Adler |
 Posted: Mon Jan 05, 2004 8:47 am |
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According to the book, Introduction to Organic Laboratory Techniques, A
Contemporary Approach", 2nd ed., by Pavia, Lampman and Kriz, "The shape of
the Thiele tube allows convection currents to form in the oil when it is
heated. These currents maintain a uniform temperature distribution
throughout the oil in the tube. The sidearm of the tube is designed to
generate these convection currents and thus transfer the heat from the
flame evenly and rapidly throughout the heating oil."
I'd like to know more about how a Thiele tube and its convection currents
work. There are two approaches: (1) A theoretical analysis of the problem;
(2) An experimental study of the detailed temperature distribution as it
varies in time. I'm more interested in the (1), although it would
be interesting to know what techniques are used for the latter. If you
know where such a study is carried out, please let me know.
Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu
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* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
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| Mark Tarka |
| Posted: Mon Jan 05, 2004 2:01 pm |
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Allan Adler <ara@nestle.ai.mit.edu> wrote in message news:<y93llom5wxs.fsf@nestle.ai.mit.edu>...
[snip...]
Quote: I'd like to know more about how a Thiele tube and its convection currents
work. There are two approaches: (1) A theoretical analysis of the problem;
(2) An experimental study of the detailed temperature distribution as it
varies in time. I'm more interested in the (1), although it would
be interesting to know what techniques are used for the latter. If you
know where such a study is carried out, please let me know.
I would theorize that this technology was
developed empirically and tested by time.
I just carried out a thought experiment --
a small piece of iodine was dropped into
a Thiele tube and the side arm gently heated
with a Bunsen Burner. I also thought that I
wore a full face safety shield, fire-retarding
full-length body protection, and heavy
insulated gloves with long cuffs. In my
imagination I believed that I saw tendrils of
color circulate within the warming oil. Hey,
it's a different window to look through :-)
If you're serious about this, you might
try checking the earliest volumes of
Chemical Abstracts in the USA, or publications
by the Royal Academies or Europe, and the Zeit...
and Bun... reports published in the German Language
during the last half of the 19th Century. But I
doubt you'll find what you want there.
Maybe someone can narrow down the span of time when
the technique was developed (presumably before
organic chemistry was recognized as a distinct
discipline, maybe even during the time of the
alchemists -- think "alembic").
There used to be popular books about the history
of science and its tools; maybe there's something
there.
Mark (...I'd bet 1800's +/- a generation or two....) |
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| Mark Tarka |
| Posted: Mon Jan 05, 2004 4:48 pm |
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Allan Adler <ara@nestle.ai.mit.edu> wrote in message news:<y93llom5wxs.fsf@nestle.ai.mit.edu>...
Quote: According to the book, Introduction to Organic Laboratory Techniques, A
Contemporary Approach", 2nd ed., by Pavia, Lampman and Kriz, "The shape of
the Thiele tube allows convection currents to form in the oil when it is
heated. These currents maintain a uniform temperature distribution
throughout the oil in the tube. The sidearm of the tube is designed to
generate these convection currents and thus transfer the heat from the
flame evenly and rapidly throughout the heating oil."
Ahem....
It's in about 1640 that the first liquid-in-glass
thermometers appear (water, then wine). Fahrenheit's
work helps to establish a temperature scale around
1714 and thermometers made by craftsmen begin to be
sold on the streets after 1780, with no commercial
production until after 1850. This info from
_Scientific Instruments of the Seventeenth and
Eighteenth Centuries and their Makers_, Maurice
Daumas; B.T. Batsford, London, Publisher.
"The use of melting points to characterize organic
compounds and their purity was introduced by Michael
Chevreul during his study of fatty acids in the 1810's.
The thin capillary tube closed at one end, still used
today, was employed by Robert Bunsen in the 1830's.
Samuel P. Mulliken at the Massachusetts Institute of
Technology published extensive tables of melting points
in his _Methods for the Identification of Pure Organic
Compounds_ (1899-1904)." _Instruments of Science: An
Historical Encyclopedia_, Bud and Warner, eds., Garland
Publishing, New York and London, 1998, p. 373.
"The most common melting point apparatus was a small
heated beaker half filled with concentrated sulfuric
acid (glycerin and mineral oil were also used) in which
was suspended a thermometer and a capillary tube held
together by a thin rubber band. The observation of the
melting point could be improved by using a magnifying
glass. Somewhat safer apparatus, which enclosed the
sulfuric acid, was introduced by such chemists as Richard
Anschutz and E.A. Schluze (1877), Carl Franz Roth (1886),
and Frederick William Streatfeild. Several improvements
were made to the melting point tube, especially the b-shaped
tube introduced by Johannes Thiele (by 1907). However, these
changes were not widely used." Ibid, p. 374.
By the 1920's the electrically heated metal block
debuts. The Sixties saw what was undoubtedly the
sort of apparatus shown in the Fisher and Sargeant
catalogs of the time, used by some of us in the labs
(Ouch! That's hot!). Now we have computer controlled
units that'll take a perfect m.p. every time. Ibid.
Mark (Please, DO NOT call Johannes Thiele, at least not
to her face  |
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| Mark Tarka |
| Posted: Mon Jan 05, 2004 7:18 pm |
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mark_tarka@yahoo.com (Mark Tarka) wrote in message news:<6b70c71c.0401051101.50bcfa83@posting.google.com>...
Quote: Allan Adler <ara@nestle.ai.mit.edu> wrote in message news:<y93llom5wxs.fsf@nestle.ai.mit.edu>...
[snip...]
I'd like to know more about how a Thiele tube and its convection currents
[snip...]
And furthermore....
M.E. Mason wrote the following, found in _Chemical
Abstracts_, v.1, May-Aug 1907, p.2064:
"Apparatus for Melting Point Determination."
J. Thiele, _Ber_., 40, 996-97. ...Upon heating
the glass loop, the acid circulates around it,
thus heating the substance rapidly and uniformly.
Mark (Oh...oh...look...look |
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| Bruce Hamilton |
| Posted: Mon Jan 05, 2004 9:30 pm |
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On 5 Jan 2004 11:01:52 -0800, mark_tarka@yahoo.com (Mark Tarka) wrote:
Quote: Allan Adler <ara@nestle.ai.mit.edu> wrote in message news:<y93llom5wxs.fsf@nestle.ai.mit.edu>...
[snip...]
I'd like to know more about how a Thiele tube and its convection currents
work. There are two approaches: (1) A theoretical analysis of the problem;
(2) An experimental study of the detailed temperature distribution as it
varies in time. I'm more interested in the (1), although it would
be interesting to know what techniques are used for the latter. If you
know where such a study is carried out, please let me know.
I suspect that the only real flow issues could arise if heat was
applied in the wrong place ( under the thermometer and sample ) rather
than under the sidearm.
Quote: Maybe someone can narrow down the span of time when
the technique was developed (presumably before
organic chemistry was recognized as a distinct
discipline, maybe even during the time of the
alchemists -- think "alembic").
I suspect the FBI confused an alembic with an almanac.
Bruce Hamilton |
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| Allan Adler |
| Posted: Tue Jan 06, 2004 11:09 am |
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Thanks for the historical comments, including references to Thiele's paper.
I'll see if I can find it.
Regarding a theoretical analysis of why it works, I have only the following
intuitions, based only on looking at a picture of one:
(1) The Thiele tube consists, essentially, of a test tube with a side arm
connected (A) near the bottom and (B) near the top of the test tube.
(2) The side arm is somewhat thinner than the test tube.
(3) Liquid in the side arm is heated more quickly than liquid in the test tube.
(4) The hotter liquid is a little lighter and the cooler liquid tends to be
found in the test tube between (A) and (B). Since the cooler liquid is
heavier (i.e. denser), it moves downward and therefore pulls the hotter
liquid at (B) down.
(5) This sets in motion convection currents which flow upwards through the
side arm and downwards from (B) to (A). Thus, the liquid moves around
the loop and its motion and heat is more evenly distributed in the loop.
(6) By way of contrast, if one merely heated a test tube, there would be
a temperature gradient from the bottom of the tube, where the heat is
applied, to the top of the tube.
(7) In more detail, between the bottom of the Thiele tube and the height of
(A), there will be a temperature gradient, and between the height of (B)
and the top of the Thiele tube, there will be a temperature gradient, but
between (A) and (B) the gradient should be very slight once circulation
sets in.
Assuming that is correct, the next questions are:
(a) how does one estimate the temperature gradient?
(b) at what rate does the liquid circulate around the loop?
(c) what is the rate at which the "equilibrium" in (7) achieved?
Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu
****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
**************************************************************************** |
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| Mark Tarka |
| Posted: Tue Jan 06, 2004 11:38 am |
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mark_tarka@yahoo.com (Mark Tarka) wrote in message news:<6b70c71c.0401051618.5cfc59b9@posting.google.com>...
Quote: mark_tarka@yahoo.com (Mark Tarka) wrote in message news:<6b70c71c.0401051101.50bcfa83@posting.google.com>...
Allan Adler <ara@nestle.ai.mit.edu> wrote in message news:<y93llom5wxs.fsf@nestle.ai.mit.edu>...
[snip...]
I'd like to know more about how a Thiele tube and its convection currents
[snip...]
And furthermore....
M.E. Mason wrote the following, found in _Chemical
Abstracts_, v.1, May-Aug 1907, p.2064:
"Apparatus for Melting Point Determination."
J. Thiele, _Ber_., 40, 996-97. ...Upon heating
the glass loop, the acid circulates around it,
thus heating the substance rapidly and uniformly.
_Berichte der Deutschen Chemischen Gesellschaft_,
40, 996-97 (1907).
139. Johannes Thiele: Ein neuer Apparat zur Schmelz-
punktsbestimmung.
(Eingegangen am 27. Februar 1907.)
Der nebenstehend abgebildete Apparat hat sich seit
zwei Jahren im StraSSburger chemischen Institut und
in einigen anderen Laboratorien bestens bewahrt.
Er besteht aus einem Rohr von ca. 2 cm Weite und 12
cm Lange, an welches ein Bogen von 1 cm Weite so
angesetzt ist, daSS er das untere Ende des Rohres mit
der Mitte verbindet. Zum Gebrauch fullt man sovielSchwe-
felsaure ein, daSS sie die obere Mundung des Bogens
gerade sperrt, wenn das ThermometergefaSS sich etwa in
der Mitte zwischen den Schenkeln des Bogens befindet.
Erhitzt man jetzt die Krummung des Bogens, so beginnt die
Schwefelsaure in dem Apparat zu zirkulieren, wie das Wasser
in einer Warmwasserheizung; in dem Rohr bewegt sie sich
dabei von oben nach unten und bewirkt ein sehr gleichmaSSiges
Steigen des Thermometers.
Der Apparat arbeitet viel gleichmaSSiger, als alle anderen
Apparate ohne mechanischen Ruhrer, er heizt sich sehr schnell
an, geht wenig nach, kuhlt sehr schnell wieder ab, und ist
durchaus nicht zerbrechlicher, als die anderen Apparate zur
Schmelzpunktsbestimmung. Da die Saure in dem Rohr ein
Temperaturgefalle von oben nach unten hat, schmelzen bei
raschem Anheizen zuerst die etwa im oberen Teil der Capillare
haftenden Staubchen der Substanz, und man kann daran leicht
erkennen, wenn man in die Nahe des Schmelzpunktes gekommen ist.
Der Apparat wird von Hrn. Karl Kramer in Freiburg i. B.
angefertigt.
There is an illustration of the device.
Mark (I do this to demonstrate what you can find
in the old lit. I located three or so reports
on what we now call the Stern-Gerlach experiment,
and with the help of some dictionaries got
reasonable translations back in 1990 or so, Now
there're on-line translation services.) |
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| Allan Adler |
| Posted: Wed Jan 07, 2004 2:15 am |
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Thanks for quoting Thiele's article. If I understand it correctly,
Thiele confirms my impression that the side arm of the tube is narrower
than the test tube part, but differs in his description of how to heat
the tube: he wants you to heat the bend in the side arm, not the bottom
of the test tube. However, his description of the convection currents
agrees with mine to the extent that the hot liquid descends from the
top of the test tube to the bottom. On the other hand, the illustration
in Pavia, Lampman and Kirz, p.496, shows the Thiele tube being heated
from the bottom of the test tube part.
Are both methods of heating the Thiele tube currently used?
Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu
****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
**************************************************************************** |
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| Bruce Hamilton |
| Posted: Wed Jan 07, 2004 2:36 am |
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Allan Adler <ara@nestle.ai.mit.edu> wrote:
Quote: On the other hand, the illustration
in Pavia, Lampman and Kirz, p.496, shows the Thiele tube being heated
from the bottom of the test tube part.
I've never seen anybody heating one from the bottom of the test tube.
The illustrations I recall in Vogel also show heating the near the bottom of
the side arm, and that's how I was taught as well.
The one we used was an inverted P with the side arm slightly smaller diameter,
and reconnecting about halfway up the main tube. The important part was to
ensure the sample and thermometer were just below the upper sidearm re-entry.
However there may be many different versions as people experimented.
Bruce Hamilton |
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| Mark Tarka |
| Posted: Wed Jan 07, 2004 10:40 am |
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Allan Adler <ara@nestle.ai.mit.edu> wrote in message news:<y93k745xdpn.fsf@nestle.ai.mit.edu>...
[snip...]
Quote: Assuming that is correct, the next questions are:
(a) how does one estimate the temperature gradient?
(b) at what rate does the liquid circulate around the loop?
(c) what is the rate at which the "equilibrium" in (7) achieved?
These are irrelevant. It is the temperature at
the sample and thermometer bulb that matter, not
at the point of heating. The process is dynamic
-- rapid heating to just below the expected m.p.
and then slooooooowly until you get the spread.
Mark |
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