Paddywhacker - 5-3-2009 at 01:50
A Dean & Stark apparatus is an extremely useful piece of kit, but, when I started out, none of my suppliers stocked it.
Instead, I found this
http://www.labwarehouse.co.nz/product_info.php?products_id=4...
The supplier calls it an Oil Determining Tube .... and it is not cheap.
It is like a Dean & Stark, but with a connecting tube that drains the water back into the reaction flask. I heated part of that tube until it was
soft and then pulled a vacuum (I sucked it) on the apparatus to collapse and seal the offending tube.
Now water does not drain back into the flask and the piece of glassware acts as a perfectly acceptable Dean & Stark apparatus.
DJF90 - 5-3-2009 at 04:26
That looks like a dean stark for heavy entrainers.
Paddywhacker - 5-3-2009 at 08:05
Woah ... then if I'd used dichloromethane instead of toluene I wouldn't have had to modify it?
Now I gotta get another.... budget permitting. Those things are supposed to be really rare.
DJF90 - 5-3-2009 at 08:09
They aren't rare, they just aren't as common as a dean stark for light entrainers, which are used for, as you say, toluene, because this is generally
more useful (higher bp of toluene vs DCM/chloroform, not entirely sure of other advantages).
chemrox - 5-3-2009 at 20:04
These come up on ebay all the time. I have five or six in different configurations. For water being evolved in a reaction in toluene I use one that
captures 10 ml water in a narrow cylinder. Iwouldn't buy the one offered here. Ge it on ebay for 10-20. If you want a stopcock make sure it is
TFE... not ground glass.
not_important - 5-3-2009 at 20:49
These are used in analytical procedures, volatile/essential oil content. Drop the material under test into the flask, add water, heat to steam
distill the oil. The oil floats on top while the water, saturated with the oil, returns to the flask. At the end, tap off the water, then the oil,
measure both for total oil if the oil has much solubility in water.
For normal DS dehydration, just open the tap whenever the water level gets too high, collecting the water in a graduated cylinder so as to track the
total amount. No need to mod the device. If you don't want to watch that closely, a photoelectric watcher could activate a stopcock turner, use a
rotary solenoid for example.
Paddywhacker - 5-3-2009 at 22:31
Thanks millions for the explanation, NI.
That means I have a simple way to steam distill a bit of essential oil from herbs and spices. Got a kg of fennell seeds in the freezer need to earn
their keep.