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Magpie
lab constructor
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Registered: 1-11-2003
Location: USA
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Mood: Chemistry: the subtle science.
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I'm not sure what you mean by a "water cooler." Is this an example:
http://www.walmart.com/ip/Ragalta-Thermo-Electric-Hot-and-Co...
The single most important condition for a successful synthesis is good mixing - Nicodem
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XeonTheMGPony
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yes the ones with the vapour compression cooling system.
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PlatinumLab
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That's more along the lines of an AC-cooling system, in which case, that's personally how I cool my water in distillations.
I built a small desktop compression unit that basically blows the air from the hotside of the coils outside, while on the cold side I have a
liquid/liquid heat exchanger which I pump my condenser water through.
I personally think it's a brilliant way to keep a condenser cold and can allow adjustable condenser temperature by adjusting the compression
differential on the hot/cold sides. It can keep the condenser cool for as long as I have electricity.
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XeonTheMGPony
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That is a very common mod in the hobby liquid cooling field. I used to fabricate custom water chillers with up to 600w capacity at -20.
I preferred to run my servers at 0c and have 13,500btuh cooling capacity.
Some point I need to make a simple 2 stage cascade system for a good cold trap, I'll use a horizontal rotary system at 500btuH.
But as I say a fast n dirty but use full cold trap can be made by moding a water cooler, it is much easier to clean and dry then a air con, especially
if one doesn't have the skill or tools to open the system and do a more proper mod of it for the application.
Most systems run on R410a now days too which is a very high pressure gas that is a near azeotrope, so if not recovered very well it will need the gas
replaced. With out looking at my tables if I recall it is siting at 200psi at average room temp!
So be care full when playing with modern air cons!
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highpower48
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What fittings do you need to make this work? 1/4" flare male fittings seem hard to get. That is 1/4" flare to a barb fitting...
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Sulaiman
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It seems that you can buy two Chinese rotary vane vacuum pumps
for the cost of a meter that can measure the pressure 
I guess that for 'serious' vacuum work you need a costly gauge,
or an un-calibrated DIY one.
From the little knowledge that I have remembered,
. unless you have a short path distillation setup there is no point going for less than a few mm absolute due to length/diameter of equipment
. if you have a short path distillation setup, with gauges, traps ...
then maybe there is a difference between a 5 pa single stage rotary vane and a 0.3 pa dual stage like I bought,
but to me there is no difference as far as distillation goes, and both are overkill for filtration.
. other interests may influence your choice,
refrigeration, thermionics, vapour deposition, clothing storage ....
I intend to make a vacuum desiccator soon so maybe my dual stage will be worth the extra ... maybe not 
your question is like " which is the best automobile to buy ? "
P.S. how to measure down to 0.3 pa with some known accuracy/error, cheaply ?
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XeonTheMGPony
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Ebay you can usually find a Supco VG46 vacuum guage for apx 100 or less. They used a fixed thermistor reference so hold calibration very well.
http://www.ebay.com/itm/Supco-VG64-Digital-Vacuum-Gauge-/172... < First hit.
http://www.ebay.com/itm/Supco-VG-60-Vacuum-gauge-/1519592630... < Much lower end one but even cheaper.
http://www.ebay.com/itm/Yellow-Jacket-69075-SuperEvac-LCD-Va... < Different brand
For fittings you want the largest practical diameter leading up to the point of use.
The deeper the vac the better the dehydration, for refrigeration water is toxic to the system, it will turn most newer oils into acids, break down the
refrigerant and block the metering device, So the standard is 500microns vacuum that holds, at this level you are assured there is no trace of water
in the system.
I like to break with OFN (Oxygen free nitrogen) then pull one more vac to be certain, for the real hard core guy for dessication you can invest in a
small cylinder of nitrogen fairly cheaply! all so use full if you want to experiment with vacuum freeze drying (One of my goals to get around too,
need to build the system for it)
With out accurate guages you may well be pissing into the wind in the pitch black!
[Edited on 24-1-2016 by XeonTheMGPony]
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Sulaiman
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I have a bid on a VG-64 on ebay UK at the moment !
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Rocket89
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What are everyone's opinion of the Chemglass CG-4800-03 vacuum pump? Found a couple used on eBay in the $200-$300 price range.
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Rocket89
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Bought a Chemglass CG-4800-03 
That is all.
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Rocket89
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Bought a Chemglass CG-4800-03
That is all.
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Axismundi000
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I'm new here so hopefully the below is relevant and useful.
I got one of the the ghast vacuum pumps (24"Hg) from Cole Palmer last summer, it had a lot of good reviews re reliability. Applying vacuum to a
distillation train after the system has settled down you definately need to close off the system with a stopcock after about 10 minutes. If not
vacuum will attenuate with continued pump operation and also you cannot switch off the pump and maintain the partial pressure.
So for vacuum distillation it is great, once the system is settled close the valve and disconnect the pump. Also it is not that noisy and it is a
diaphragm pump so no oil needed.
For continued usage where you cannot close off the system once vacuum established and you need to maintain highest vacuum this would not suite ( it
wasn't a cheap pump).
So the main question then is perhaps the specific needs that the pump must satisfy. For vacuum distillation the one I got is fine because I just use
it for distillation.
Has anyone tried the Ventuuri vacuum valves? I considered those because of potentially much better vacuum but I was concerned that thermal
decomposition might occur before heating of the boiling flask established partial pressure in the system. If thermal decomposition at low temperature
is not an issue they are a fraction of the cost.
[Edited on 30-1-2016 by Axismundi000]
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EugeneOregon
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Quote: Originally posted by Heavy Walter  | Hi Rocket89
Me too an old lurker and a new member.
I have a small high vacuum lab and planning some chemical synthesis.
Think of having two vacuum systems: a simple water jet for filtering and low requirements, easy (in case you have running water close to) and an
elaborated system (two-stage rotary pump plus diffusion pump -air or water cooled) with high-vacuum reading.
The high vacuum system will be helpful for delicate syntheses.
Don't need to buy new ones: e-bay offers are interesting and cheap.
Water jets come in glass, plastic or metal, no too expensive.
High vacuum is tricky: leaks are common and pinpointing them not so easy. You will have to do your own practice.
Feel free to ask me any doubts.
Can send you some images.
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I am from Oregon and in my retirement from disability I have adopted a great hobby of purifying cannabinoids out of the available and legal marijuanna
extracts from dispensaries.
Step One is Dry Column Vacuum Chromatography. (DCVC), which is my adaptation of the DCVC method demonstrated by the University of Coppenhagen.
My video showing this is here:
https://www.youtube.com/watch?v=BIsiCfcLBL4.
The only good pump for DCVC is a diaphragm pump and I chose a PTFE economy pump for the vacuum through the column during DCVC which draws a lot of
fume because the column is drawn dry between solvent gradients. When I used my dual vane cheap rotary pump it pukes out a vapor that fills the room
which is a fine aerosol of oil mist attaching to fume as the fume passes through the oil.
Step two is heated solvent purge under low vacuum provided by the PTFE pump. The fumes pass through the oiless daphragm pump and into a collection
flask. Pump is unaffected by Hexanes, Ethyl Acetate, and alcohols used.
Step three is molecular distillation. This is the big one. You must be able to pull a vacuum down to 20 microns or less IF you hope to distill delta 9
THC and the other medicinal cannabinoids at temperatures listed in scientific journals. Pubchem lists THC (Dronabil) boiling point as 200C and .02 mm
Hg (Torr). This is also stated as 20 microns. Very deep vacuum was achieved in my home hobby lab with my Edwards EM 28 outfitted with stainless steel
bellows and fittings. I got the EM 28 from craiglist for $1000 and two oil changes and running the ballast wide open has returned the unit to factory
specifications. I cannot emphasize the importance of being able to maintain a deep vacuum for molecular distillation. I have demonstrated in the video
link below a technique for measuring the boiling points of cannabinoids. First drip into collection bulb noted at 140C on flask thermometer suspended
one inch above puddle.
Using a single point conversion chart to make a crude estimate of likely boiling points reveals from this information that the temperature limit on my
spherical cloth heating mantle of 400C will easily be exceeded at just 75 microns (.075 mm Hg). The heating mantle is just 60 watts and this is way
more than enough IF you can pull down to this level and hold it. I believe this video is the first on youtube demonstrating decent precision measuring
cannabinoid boiling temp and pressure data.
https://www.youtube.com/watch?v=rD5tIdnDNl0
Short answer to your question is I use three pumps, each well suited for their niche use but nearly useless outside their niche. Using the deep vacuum
pump to attempt solvent purge means you will suck a lot of compound up into the uptake tube and purging rig from violent bumping. Then the pump oil
needs decontamination procedures. The roughing pump, a $250 dual vane pump, is perfect for my one quart vacuum chamber used to purge trace solvents
from medicine under low heat and high vacuum. Oil must be changed in the roughing pump after each use as it has no gas ballast but the pump pulls down
to 75 microns which easily purges trace solvents and has the advantage that those solvents do not decontaminate the deep vacuum pump, hose, or pirani
sensor used in it and brand new replacement is just a few hundred dollars.
You must read and understand the technical specifications on the pump and you must know what vacuum you need to achieve and what type of vapor load
you plan to see. Ultimate vacuum is listed and rate of evacuation in cubic feet per minute will be listed. Ultimate vacuum is how much vacuum it pulls
when the inlet line is blanked off. CFM is a bit trickier to explain because of (among other things) the time (integral) factor involved. As the
vacuum becomes deeper the flow from the furthest part of the vaccum system towards the pump chamber become slower and then there is no "flow" at all
of the compound being molecularly distilled. Gas does not "flow" as a fluid under conditions that I create during molecular distillation at one micro
or less. In that state when the phase transition occurs the gas molecule takes off in a random brownian direction and continues in a straight line
until it hits something. This repeats so that eventually the molecule finds its way out of the boiling vessel.
Leakage at molecular distillation vacuum levels is a factor and represents that which "flows" in a system under deep vacuum. ANY polymere seal has
permeability and leakage. Any glass joint has leakage despite grease. I do not know how to compute the way to select the right CFM under these
conditions precisely except to say that it can be expressed as "tonnage" which roughly translates into work capability. Tonnage is estimated by CFM
squared. So a .9 CFM pump creates .81 tonnes of work while my 26 CFM Edwards creates 676 tonnes.
In the marijuanna industry here in Oregon refineries that use a common Welch pump rated at .9 CFM pump, at .81 tonnes, typically run up to 100C higher
in their online videos than my experimental rig that runs a pump with the exact same ultimate vacuum rating as a practical matter but at 26 CFM which
creates 676 tonnes of work to pass the leakage out of the system. This suggests that a curve could be plotted if more tests with different pump
tonnage ratings were conducted but I have not seen any definitive table of data doing this and regarding the relationship between CFM and target
vacuum level during molecular distillation as carried out at or near the ultimate vacuum of the pump which is under one micron (during which the only
"flow" out of the system is leakage).
Forgive my long winded answer but I never got good at stopping at pne sentence...
Good luck
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