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G-Coupled
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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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S.C. Wack
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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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j_sum1
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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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Tellurium
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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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Heptylene
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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.
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.
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Sulaiman
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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.
CAUTION : Hobby Chemist, not Professional or even Amateur
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Heptylene
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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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Heptylene
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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.
 
[Edited on 9-12-2019 by Heptylene]
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G-Coupled
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Ooh, very interesting details. Thanks for posting!
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SWIM
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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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Heptylene
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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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CharlieA
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@SWIM: It sounds like you need to invest in some glass-blowing equipment!
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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Sulaiman
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Thanks, I see it now,
and
the tapered notch in the stopcock can also be found on some (older) burette stopcocks.
CAUTION : Hobby Chemist, not Professional or even Amateur
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SWIM
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Quote: Originally posted by CharlieA  | @SWIM: It sounds like you need to invest in some glass-blowing equipment!
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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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.
[Edited on 10-12-2019 by SWIM]
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B(a)P
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My latest purchase, nothing exciting, but all decent quality. I have sworn off cheap glass.
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G-Coupled
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What troubles were you having with cheaper glassware?
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B(a)P
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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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G-Coupled
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Was it Chinese no name stuff, or a brand like Ninshin or whatever?
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B(a)P
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Chinese no brand, roll the dice and take your chances purchase. It was sold as borosilicate glass.
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arkoma
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A full face organic respirator!!
"We believe the knowledge and cultural heritage of mankind should be accessible to all people around the world, regardless of their wealth, social
status, nationality, citizenship, etc" z-lib
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morganbw
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Paint store?
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arkoma
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ebay
"We believe the knowledge and cultural heritage of mankind should be accessible to all people around the world, regardless of their wealth, social
status, nationality, citizenship, etc" z-lib
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j_sum1
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I am now the proud owner of a range of volumetric flasks: 1×1000mL, 2×500mL and 4×100mL.
Something that I have been meaning to get for a long time. I feel like a scientist now and I can pretend to be half-way accurate in what I do.
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j_sum1
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Thread Topped
7-3-2020 at 21:46 |
Sulaiman
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I was recently given a 2-neck (34/35 & 19/26) 5L rbf with 700W heating mantle and three retort clamps with stands ... lovely
Unfortunately other parts of this kit have not materialised,
and all of my chemistry stuff is in UK, so I can't do much,
... I've ordered a few things;
. a 19/26 thermometer adapter https://shopee.com.my/19-26-Thermometer-Adapter-Inlet-Adapte...
. a -10 to +110 x0.5 oC mercury thermometer https://shopee.com.my/READY-STOCK-Thermometer-Mercury-Lab-Us...
. 24/35 to 24/29 adapter https://www.ebay.co.uk/itm/Glass-Reducing-Adapter-From-34-35...
. a cheap Chinese '1000ml Distillation Kit' https://shopee.com.my/Teamwinm-Distillation-Apparatus-Lab-Va...
At least I will have a Vigreux column to compare HETP with my usual Hempel columns.
I already have more than one distillation kit at home, this is just temporary setup.
Now to start a sugar wash fermentation so that I can distill some EtOH for hand sanitizers.
Hopefully I can get product before the covid pandemic dies out.
CAUTION : Hobby Chemist, not Professional or even Amateur
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Sulaiman
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just curious ... B, A, USP ? certificate ?
I ask because previously I mostly had second hand volumetric flasks,
I bought a new Pyrex A/USP 100ml vol.flask recently,
the date and batch code are printed on the bottom of the flask,
and from the scilabware website I downloaded the batch certificate.
Interesting ...
the specifications are 100ml +/- 0.08ml In@20oC
the batch certificate gives 100.021ml +/-0.014ml (1 std. dev.)
... much better than the basic spec.
(but maintaining similar accuracy over a few operations is tedious)
_______________________________________________________________________
I found the cheap polypropylene volumetric flasks available from China via eBay to be very useful
as flower vases ... definitely not for anything near an accurate volume.
CAUTION : Hobby Chemist, not Professional or even Amateur
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