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Author: Subject: latest glassware purchase
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[*] posted on 25-11-2019 at 14:38


You find Deschem's quality to be OK then? I was wondering if it might be worth springing a bit extra for the ProGlass Chinese stuff which is about 30-40% more money, but the quality is allegedly up there next to Euro brand glass.
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[*] posted on 25-11-2019 at 16:37


I'm not sure what if any size standards the Chinese follow with their RBFs. They seem incapable of making glass that conforms to US sizes and mantles, and probably Chinese garbage mantles as well. Their other glass is approximately meh.

Thick glass does not equal quality
Thick glass does not equal quality
Thick glass does not equal quality




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[*] posted on 25-11-2019 at 16:53


Deschem seems to be reasonably well regarded. Those with a fetish or need for high end stuff will go for something else. Those who break things and have a budget are happier with Chinese glass and Deschem is one of the better suppliers. Their customer service is good even if the glassware itself is a bit variable.

Nanshinglass and Reacware are also comparable, or maybe slightly ahead of Deschem.
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[*] posted on 25-11-2019 at 19:17


Until now I had a good experience with deschem, the quality is quite reasonable. The price is really unbeatable compared to european glassware, at least when buying stuff with ground joints. Nearly all of my ground glass stuff is from deschem, the beaker and stuff like that are cheaper to buy here. I had european 29/32 glassware before, but because deschem only has 24/40 and 24/29 I switched mainly to 24/29. The joints fit well into each other. I heard of some problems when using different parts from different suppliers, but my 29/32 glassware has a good fit with the 24/29 deschem glassware(I'm using joint adapters from VWR and the other 29/32 stuff is mainly Duran/Schott). Maybe I'm just lucky until now or others have been unlucky, but so far the whole experience with deschem glassware is the same as with other glassware.
The only bad thing are the rubber sealings in the thermometer adapters. They are useless after a few runs - especially with oxidizing chemicals in there, but I just use teflon tape instead of the rubber ring ;) Also the thermometers I got maybe two years ago were pretty inaccurate, they showed boiling water to be 90°C. But the new ones I got a week ago seem ok(98°C for boiling water).

[Edited on 26-11-2019 by Tellurium]

[Edited on 26-11-2019 by Tellurium]
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[*] posted on 6-12-2019 at 14:12
Distillation head!


Christmas came early this year, I found a very nice partial-takeoff distillation head for $100 on ebay! Shipping + customs taxes puts the total just over $150. Probably the best deal I've ever made considering these retail for around $700 new from a glassware supplier. It's in perfect condition, except for a broken stopcock thread and some rotten stopcock nuts, o-ring and washers.

distillation head.JPG - 1.1MB

This particular design is the one of Rehn and Theilig. (Figure from E. Krell's Handbook of laboratory distillation, 2nd ed., p. 392)

Vapors condense on the "intensive" condenser and fall down on the oblique weir just above sideway joint. This diverts the condensate to the horizontal arm with two stopcocks. Stopcock 1 precisely controls the reflux ratio: the distillate that doesn't go through this stopcock falls back over the weir into the column. Stopcock 2 is there to start or interrupt product withdrawal without modifying the reflux ratio.

The receiving flask is connected to the joint on bottom right, possibly through a condenser to cool the product further. Stopcocks 3 and 4 allow changes of receiver during vacuum distillation without disturbing the column. Hose barb A is connected to a vacuum source, and hose barb B to the atmosphere or some other gas.

Rehn-Theilig design.JPG - 111kB
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[*] posted on 7-12-2019 at 03:18


Looks like a useful piece of glassware, nice condenser.
To satisfy my curiosity, could you show a close-up of the weir/bottom of the column,
I can't see how the refluxed liquid gets back to the column.




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[*] posted on 7-12-2019 at 06:29


I'm don't have access to my lab right now, but I'll post close-up shots later. The oblique plate is actually perforated in the middle. It's kind of difficult to see here. The liquid fills up the left side of the small tube with two stopcocks and overflows through the large hole in the plate, and drips down into the column. The reflux-adjusting stopcock has an interesting design for very small flowrates, I'll show it as well.
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[*] posted on 9-12-2019 at 12:31


As promised, a picture of the weir inside the colmn. As you can see, the condensate flowing on the walls of the condenser is diverted into the side tube. This also explains the choice of condenser design: A regular Dimroth condenser where condensation drips down from the coil in the center (and not the walls) would not work for this as it would miss the weir.

Also a closeup of the reflux ratio stopcock. Small notches on both sides of the stopcock bore (not chipped, it really is designed like that) allow very small flowrates to be let through when the stopcock would normally be in a "totally closed" position. Unfortunately the thread on this one is broken, so I might replace it with a PTFE one which I will modify to also have those notches. A really nice detail, and I think this would work well on an addition funnel for very slow addition rates.



reflux stopcock detail.JPG - 165kB weir detail.JPG - 616kB

[Edited on 9-12-2019 by Heptylene]
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[*] posted on 9-12-2019 at 14:22


Ooh, very interesting details. Thanks for posting!
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[*] posted on 9-12-2019 at 14:54


Quote: Originally posted by fusso  
Quote: Originally posted by SWIM  
Just received a 25 plate vacuum jacketed 29/42 Bruun column.
Whats that for?


For distillations.

They're like Oldershaw columns, but the return tubes are outside the central column (but inside the vacuum jacket if it has one.)

They have throughput rates that are very high, and are supposed to be very good for fractionating solvent mixtures like hydrocarbons etc.

I'm probably going to try stripping the jacket off and fixing the internal column. Obviously, I don't have a hope in hell of re-jacketing it, but a 25 plate un-jacketed Bruun would still be better than nothing. If I do this I'll be able to post some pictures of it out of the jacket.

I have had terrible luck with distillation equiment for a year now.
I sold 2 of my best columns because I couldn't resist the profit, and figured I'd get more soon enough. No such luck. 3 have come broken, and 2 were not what I thought they were, but some other items so obscure I'm still not sure exactly what they're for.

Note: I just got a vacuum distillation receiver from the same guy that was broken too.

And I'm waiting on a Widmer column about 2 feet long, also from the same guy...

I wonder how many pieces THAT is gonna be in.




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[*] posted on 9-12-2019 at 15:03


Nice find SWIM! Though Oldershaw and similar columns have a large hold-up correct? What kind of scale do you run your distillations at? I imagine for anything less than a few liters of starting material, the holdup must be too great to be viable.
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[*] posted on 9-12-2019 at 16:35


@SWIM: It sounds like you need to invest in some glass-blowing equipment!:D Seriously, you might check the local university chemistry department to see if they have a glass blower on staff who can repair some of your things...or if they don't have one on staff, perhaps they can refer you to one.



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[*] posted on 9-12-2019 at 16:59


Quote: Originally posted by Heptylene  
As promised, a picture of the weir inside the colmn.

Thanks, I see it now,
and
the tapered notch in the stopcock can also be found on some (older) burette stopcocks.




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[*] posted on 9-12-2019 at 20:41


Quote: Originally posted by CharlieA  
@SWIM: It sounds like you need to invest in some glass-blowing equipment!:D Seriously, you might check the local university chemistry department to see if they have a glass blower on staff who can repair some of your things...or if they don't have one on staff, perhaps they can refer you to one.





I've been meaning to pick up an oxygen generator and torch for small repairs, but I suppose I ought to see how much getting the Bruun worked on by somebody competent would cost.
I don't think they're better than Oldershaws, but they're mighty uncommon and I'd Like to have one in working condition.

@Heptylene: I think Bruuns have a lot of holdup, but I haven't used one.
This is literally the only one I've had a chance to buy and it came broken.

I do have flasks and mantles up to 5 liters, but I was planning on using 3 liter because I have spherical mantles in that size and want to try them out.

BTW: here's what a Bruun without the outer vacuum jacket looks like.
Re-reading this post it occurred to me that my descriptions were probably confusing.















Bruun column, no jacket..jpg - 21kB

[Edited on 10-12-2019 by SWIM]




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[*] posted on 16-1-2020 at 00:18


My latest purchase, nothing exciting, but all decent quality. I have sworn off cheap glass.

IMG_20200116_190939.jpg - 4.6MB
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[*] posted on 16-1-2020 at 12:32


Quote: Originally posted by B(a)P  
My latest purchase, nothing exciting, but all decent quality. I have sworn off cheap glass.


What troubles were you having with cheaper glassware?
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[*] posted on 16-1-2020 at 15:21


The last straw was losing 1 L of dissolved ammonia nitrate and calcium sulfate precipitate all over my bench and floor. I was half way through an ammonia nitrate synthesis and got slightly over zealous stirring with a glass rod, tapped the side wall of the breaker and it broke a piece out of the base of the wall of the breaker.
I have also had issues with cheap glassware cracking when on the hotplate.
I have never had an issue with Simax.

[Edited on 16-1-2020 by B(a)P]
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[*] posted on 16-1-2020 at 19:50


Was it Chinese no name stuff, or a brand like Ninshin or whatever?
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[*] posted on 16-1-2020 at 22:37


Chinese no brand, roll the dice and take your chances purchase. It was sold as borosilicate glass.
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[*] posted on 19-1-2020 at 12:44


A full face organic respirator!!



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[*] posted on 19-1-2020 at 15:30


Quote: Originally posted by arkoma  
A full face organic respirator!!

Paint store?
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[*] posted on 19-1-2020 at 17:01


ebay



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