Sciencemadness Discussion Board

Dean-Stark trap ?

aga - 12-5-2016 at 00:35

This brand-new £7.28 inc shipping item looks pretty dean-starky to me :

http://www.ebay.co.uk/itm/381569370564?_trksid=p2057872.m274...

dean.JPG - 56kB

Eosin Y - 12-5-2016 at 00:57

What would you usually use a Dean-Stark for?

Volanschemia - 12-5-2016 at 01:27

Looks very Dean-Starky, aga. I might even grab one.

@Eosin Y, https://en.wikipedia.org/wiki/Dean-Stark_apparatus

Eosin Y - 12-5-2016 at 01:35

Thanks. So this would be useful for something like separating ethylene glycol from water in antifreeze or something? I might grab one too, as it might be useful and it's a low price.

aga - 12-5-2016 at 01:38

It might need tipping to the side a bit to work.

I have a 'proper' one (but without the stop-cock) and the arm is slightly angled downwards.

For that price it's a steal !

j_sum1 - 12-5-2016 at 01:42

Score!

Got me one.
Quote: Originally posted by Eosin Y  
What would you usually use a Dean-Stark for?


1. Purifying immiscible substances that have an azeotrope with water. Toluene is an example. Barely soluble in water but has an azeotrope.
2. Dehydrating substances that are temperature sensitive. Oxalic acid dihydrate is an example. You can't just heat it to drive the water off. But if you dissolve it in toluene you can drive off the water using the toluene water azeotrope and return the toluene back to the original flask. Then you have a dry solution of the oxalic acid which you can then use to form the anhydrate.
3. Essential oil distillation -- which is what this one is advertised for. You could I guess use a sep funnel but the volumes you are working with make it not really workable. The Dean Stark does a better job and does it continuously as you perform your steam distillation.

Probably other uses as well. I have never used a DS trap but have been intrigued by the process. There have recently been a couple of good videos on it from Nurdrage, NileRed and I think also Doug's Lab as well. At this price, how could you turn it down?

careysub - 12-5-2016 at 05:42

For US eBay:
http://www.ebay.com/itm/24-29-50ml-Glass-Oil-Water-Receiver-...

Cheaper even than the UK listing.

[Edited on 12-5-2016 by careysub]

gsd - 12-5-2016 at 06:16
Quote: Originally posted by Eosin Y  
Thanks. So this would be useful for something like separating ethylene glycol from water in antifreeze or something? I might grab one too, as it might be useful and it's a low price.


You won't need DS to separate EG from Water. A simple column will do the job as the BP of EG is 197 Deg C.

Amongst its several uses, I use it to remove reaction water from immiscible lighter solvent which is refluxed back to the rection flask.

BTW there is a modified version of DS which can be used for solvents heavier than water. IIRC it is described in Vogel.

gsd

This image is from the net not from Vogel

a0001248.jpg - 8kB

[Edited on 12-5-2016 by gsd]

XeonTheMGPony - 12-5-2016 at 07:04

I'd rather spend the extra bit to get a proper graduated one. You can't work blind as I say, good steal if you do not need to track any results.

Good grab for those who like toys though for sure, great find.

http://www.ebay.ca/itm/15ml-24-40-Glass-Distillation-Receive...

One I plan to get.

[Edited on 12-5-2016 by XeonTheMGPony]

Dr.Bob - 12-5-2016 at 07:35

That is a comically low price for any glassware, it is amazing how cheap things are in China, plus they subsidize the postage rates for exported goods, so it costs almost nothing to mail things out of China.

I can't blame anyone for buying things that cheap, but if anyone in the US wants a Dean Stark, I have several in 29/42 size, which I would sell cheaper than for a 24/40, since they are so uncommon a size. I can even thow in an adapter. It is not worth selling them to Europe, Asia or Aust, from here, as the US has raised postage so much in the last couple years that shipping anything out of the US is way too expensive. Does that maybe help explain the trade imbalance with China? I can buy items from China with shipping for much less than just the postage cost to ship the same size/weight package back to China. That is just wrong.

XeonTheMGPony - 12-5-2016 at 08:47

Quote: Originally posted by Dr.Bob  
That is a comically low price for any glassware, it is amazing how cheap things are in China, plus they subsidize the postage rates for exported goods, so it costs almost nothing to mail things out of China.

I can't blame anyone for buying things that cheap, but if anyone in the US wants a Dean Stark, I have several in 29/42 size, which I would sell cheaper than for a 24/40, since they are so uncommon a size. I can even thow in an adapter. It is not worth selling them to Europe, Asia or Aust, from here, as the US has raised postage so much in the last couple years that shipping anything out of the US is way too expensive. Does that maybe help explain the trade imbalance with China? I can buy items from China with shipping for much less than just the postage cost to ship the same size/weight package back to China. That is just wrong.


I'd love to get stuff from USA suppliers but the shipping is akin to rape! For a 5 dollar part some are quoting 30 + dollars for shipping! when that part is the size of a potato chip!

I just can not justify that!

Texium - 12-5-2016 at 08:52

Regarding the use of a Dean-Stark trap, I have one and I've only used it once, but it was quite helpful when I did need it. I used it when I was making p-toluenesulfonic acid. As mentioned upthread, toluene and water are immiscible but form an azeotrope. In the reaction between toluene and sulfuric acid, p-toluenesulfonic acid and water are formed, so the reaction is driven forward if water is removed. With the Dean-Stark trap, it is very easy to remove water while the toluene that is collected flows back to the reaction flask. Very nice to just sit back and watch it go.

Fulmen - 12-5-2016 at 11:01

They are also quite useful for soxhlet extractions of wet material.

aga - 12-5-2016 at 11:07

What does that setup look like ?

Fulmen - 13-5-2016 at 03:31

Something like this:
585150.jpg - 12kB

careysub - 13-5-2016 at 06:13

The Dean-Stark + Soxhlet arrangement would require a very specialized Dean-Stark trap, or (more likely) a similarly specialized adapter since the upper joint on Soxhlet extractors are huge and often odd sizes (40/38, 50/42, 34/45, 45/50, 55/50, etc).

Texium - 13-5-2016 at 06:48

Interesting! I want to try that now. I have a small 34/45 Soxhlet and a 34/45 to 24/40 adapter, so I could actually set that up.

What would be a specific example of something that you would use that apparatus for?

Fulmen - 13-5-2016 at 08:01

I've used it a couple of times for toluene-extraction of wet (moist) material. Useful if you're worried about loosing volatile components or simply want to dispense with a separate drying process. It was a purpose-made adapter, not dissimilar to the one depicted.

careysub - 24-5-2016 at 08:15

I ordered one of these from playtle on eBay (only $10.24 shipping included) but it was shipped in semi-soft packaging that is manifestly inadequate to protect that very fragile side arm, and it arrived broken off. I cannot imagine these things ever get through unbroken the way it is being packaged.

I am currently corresponding with the seller about addressing this.

Just thought I would give a heads up if others want to order this. I will post how this comes out.

It is cheap enough for write-off so it is not a big deal.

Dr.Bob - 24-5-2016 at 09:14

If anyone really wants to do this well, I do have one 45/50 Dean-Stark that I remembered when I saw the photo above, I also do have a few Soxhlet apparati as well, in several sizes. It has taken me a while to find matching tops and bottom sets, as they make them in about 5 or 6 various joint sizes on the condenser bottom. The 45/50 Dean Stark holds at least 100 ml, so using it only makes sense with a pretty large bottom flask and a large scale extraction. I have a few other 45/50 joints adapters as well, gas inlets, claisen, dist head (I think), and some other large stuff, but just one box of it. Not sure how much demand there is for that size glassware.

the other half

Sulaiman - 24-5-2016 at 09:56

the glassware poined to above
has a sibling http://www.ebay.co.uk/itm/24-40-Glass-Oil-Water-Receiver-Sep...

one to remove the less dense liquid, one to remove the more dense liquid.

aga - 2-6-2016 at 11:29

Mine arrived today.

Not sure it was supposed to arrive as a kit of parts :(


brokensmall.jpg - 36kB

careysub - 2-6-2016 at 11:55

Exact same condition as mine.

The way they are packing these things they CANNOT arrive unbroken!

The mailer their are using is a Tyvek envelope containing one of these:
http://www.alibaba.com/product-detail/Hot-china-products-who...

The air tube are rigid along their length, but they flex rather easily side to side, and thus the side arm WILL get broken off.

aga - 2-6-2016 at 12:06

Quote:
but they flex rather easily side to side

Yep. Seems to be exactly because of that.

It's a real shame as the Quality of the glass & ground-glass valve all seems pretty high.

A couple of pieces of cardboard could have saved it.

[Edited on 2-6-2016 by aga]

Marvin - 2-6-2016 at 13:01

Quote: Originally posted by XeonTheMGPony  
I'd rather spend the extra bit to get a proper graduated one.

http://www.ebay.ca/itm/15ml-24-40-Glass-Distillation-Receive...
[Edited on 12-5-2016 by XeonTheMGPony]


The graduations are the wrong way round. They start at 0 part way up, not even the level of run off, and go up as you go down.