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Chris The Great
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[*] posted on 13-2-2005 at 02:19
Glassware Questions


I recently acquired a fair sum of money, and wish to get a complete vacuum capable distillation setup. However, I lack any experience with lab glassware types (other than that Bomex = things breaking) and the different advantages/disadvantages that different things have. Because there are a lot of you guys who have experience and knowledge vastly exceeding mine on this subject, I have some questions. Hopefully none are simple other than the first one, I have only heard that once on this board, so I wanted confirmation. I have decided on a 24/40 setup, as this seems to be the most common size of glassware, most of which I hope to buy from United Glass Tech, as according to the thread on Cynmar they are the best and cheapest for vacuum capable distillation setups. I am planning on buying their complete distillation apparatus http://unitedglasstech.com/distillation.htm if a 200mm condenser is all I need, to save a few bucks.

1: I've heard that flat bottom flasks cannot be used for vacuum distillation, is this true? I suppose it would be the uneven pressure on the flat bottom.

2: The Liebig condenser http://unitedglasstech.com/ugt2004onlinecatalog/Distilling/D... - is there any need to get beyond a 200mm one? They sell 400 and 600mm ones, at much higher prices, and I'm wondering if there is ever need for such a long condenser, or would it be best to just stick with the 200mm, which is what I am thinking is the best (and cheapest).

3: The Vigreux column http://unitedglasstech.com/ugt2004onlinecatalog/Distilling/D... - this one really has me stuck, as I know absolutely nothing about what length would be best. 200mm seems to be small, 400mm looks better, 600mm looks best, but do I really need a 400 or 600mm column, or would it be best just to get it now so I won't have to buy a longer one when I start doing more requiring experiments. Some experiments I plan to do however require a "efficient column" which I assume to mean 400 or 600mm. But that will also slow down distillation for things that do not need such a long column, so, should I get the longer ones, and if so, what length?

4: Lab stands- is there anything special about these or should I just get the cheapest available, and what type of clamps should I get? Assuming I'm using the below setup for heating, is one stand enough (one clamp to hold the vigreux, another to hold the receiving flask and a ring support for the receiving flask) or would it be best to get two?

5: Heating- I'm planning on using a Crockpot (for making stew) to heat an oil bath. Some modifications will be made to the heating controls of course, apparently these can get to 250C without a problem, I assume this will work well for distilling with a small stand for the flask? It also means I can be cheap, as old Crockpot's, oil and a simple stand are dirt cheap.

6: Thermometer- UGT wants $30 US for a thermometer, which I am simply not going to pay! Especially since I need two thermometers, one for <115C, and one for above that. Is there anything special about these? Surprisingly, Cynmar http://www.cynmar.com/advanced_search_result.php?keywords=th... sells mercury thermometers for 1/10 of this price, and up to 1510C :shock: so I am probably going to buy it from them. Is there a catch, or is it just a good deal?

7: Rubber tubing- Since I need rubber tubing both to connect to the condenser and for other experiments, what size is best? 3/16 inch inner diameter? I'm planning on buying the black rubber tubing from Cynmar http://www.cynmar.com/index.php?cPath=199_163_279 with a 3/16 inner diameter and 1/16 inch wall, or would a 1/32 inch wall work fine for low pressure etc?
On a related note, 6mm outer diameter glass tubing is the standard size, right? That's what an old home chemistry book of mine says, I assume it's still true.

8: Vacuum tubing- Cynmaer doesn't sell it, UGT doesn't sell it, where should I go for it?

9: Aspirator- I don't want to make one myself, so I figure I'd buy one from Cynmar http://www.cynmar.com/advanced_search_result.php?keywords=as... . The stainless steel one is what I'm looking at, as it should not be affected by nitric acid etc and most other chemicals. Or am I mistaken?

I am also wanting to buy a reflux condenser http://unitedglasstech.com/ugt2004onlinecatalog/Condensers/c... , however I don't have enough money at the moment. However, since I figure I might as well figure this all out now, what would be the best length for refluxing compounds with a fairly low bp (ie <30C). I plan on trying several procedures which will need that, so I assume a longer condenser would be best in this case? And what is the difference between a Graham and the Reflux Condenser? Aren't they the same? If they are I'll just buy the 500mm Graham from Cynmar http://www.cynmar.com/index.php?cPath=187_83 .

So many questions....hope they aren't too simple.
Thanks alot.
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[*] posted on 13-2-2005 at 07:40


Take a look at their ebay auctions, too. Their ‘distillation distilling’ setup is the same thing with a couple more things (stopper, thermometer, free shipping) for a few dollars less.

1. Yes, it’s true.

2. I’ve found my 200mm liebig adequate for distilling things.

4. No, there’s nothing special. I use two stands and four buret clamps. One for the boiling flask, one for the top of the 3-way adapter, one for the receiving flask, and one for the bent adapter, although I’m not sure if that one’s really necessary.

5. If I were you, I’d get a cheap heating mantle from ebay and a suitably sized flask (with a normal wall, not UGT’s thick walls) for non-vacuum distillation. Don’t use cheap cooking oil for heating, it stinks up the house well below 200*C.

6. Yes, go with Cynmar. Get an NIST thermometer, that Ertco stuff is junk (Ertco = +/- 2*C, NIST = +/- 0.1*C). I think you’d want a total immersion thermometer, as PI ones are very touchy about where exactly you put the bulb. With a TI, it should be fine as long as the vapor completely surrounds the mercury. (If anyone knows better, please correct me.) By the way, the thermometer UGT gives you with their setup is a PI.

7. No, get the ¼” ID stuff.

9. Looks good.

As for the condenser, you definitely want one with a 24/40 joint. Cynmar’s condensers don’t have joints. In a grahm condenser, the cooling water goes around the spiral, while in a reflux condenser, it goes through the spiral. You can’t use a grahm for refluxing.
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Marvin
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[*] posted on 13-2-2005 at 08:07


1. True. Flat surfaces do not resist pressure well. Flat sheet of A4 paper cannot support its own weight supported from both ends, but roll it into a tube and its fine. Into a vertical cone and it can support full tins of soft drink.

2. Depends what you are distilling and how rapidly. 200 or 300mm should be fine for most jobs but for an ether reflux its worth using a double wall condensor. Impotantly, don't get an expensive one alone as using it all the time will end up costing you more money. I suggest you buy a 200mm or 300mm and if you need a better one later on, buy one then.

3. I am not fond of these and what you need will be totally dependant on what you are doing. I would go with a shorter plain column with a packing support. Vigreux is very wasteful and if you buy a long column for high separation and then need to distill a high boiling point oil, you wont be able to insulate the column well enough. You can pack a plain column with broken glass and it will work a lot better provided you dont crowd out all the gaps. If you dont have an idea what you are going to be separating, then dont buy one at this stage.

4. The lab stands and clamps need to be rock solid. You can add cross bars to make a lattice, and screw the bases to the desk if need be, but as a guide, I'd say 'heavy' and 'steel'.

5. Dispite the cost I would go with heating mantles. They can be made to cover several sizes of flask by packing the exposed areas with glass wool (Dont insulate the flask from the mantle!). Oil baths are messy and unpleasent to use. Find a cheap mantle and controller or you will probably spend more time trying to clean oil off everything than doing actual chemistry.

For small distillations of 'safe' substances (high boiling boint or non flammable), I generally use a bunsen or a micro burner, particulally for pear shaped flasks which tend to be better for small amounts.

6. Thermometers tend to come in all flavours and prices from insane glass jointed NIST calibrated prices to cooking thermometers. I'd use the latter with a screwthread adaptor. Most important thing is that you know when the temp is changing, and that you can compare the temps of several runs. If several thermometers dont agree closely label them, A, B , C etc and note the letter next to each temp reading. If an accurate absolute value becomes important you can convert at a later date.

7. Depends on your condensor. You may also want to think about cable ties to help keep it on. It needs to be a totally reliable connection. I have no idea what you mean by standard glass tubing, since quickfit I dont think anyone uses glass tubing for connections anymore.

8. Rubber tubing will usually not work at all with low pressure and the extremely thick wall stuff is far too expensive for my liking. Try places that sell semirigid tubing for fish tanks, depending on what you are distilling and how much of that you expect to go beyond the condensor.

9. Go with polypropylene, stainless steel is needlessly expensive and the PP ones stand up to a lot of lab abuse. It doesnt need to last forever.

For general reflux just use the Liebig. If its ether then a double walled condensor is best. What they call a 'reflux style' is what everyone else calls a cool coil. The water is run through a coil in the middle which condenses the rising vapour. Graham condensor is inside out, the vapour rises through the coil of glass and the cooling water circulates around the outside. Graham is going to choke on even small amounts of liquid, its not generally useful.

I hope this is helpful.

Edit, the only part of neutrino's post I would disagree with on tecnical grounds would be the use of a total immersion thermometer. These expect the whole length to be at the same temperature. A partial immersion will have a line on the stem a few inches at most above the bulb and only the lower part needs to be at the measured temperature. As the bulb in distillation should be level with the vapour offtake most of a long thermometer will be outside so a partial immersion will give the more accurate result. A total immersion not totally immersed may as well have been calibrated by Mickey Mouse as NIST though this wont affect relative work which as Ive said is all I consider important.

[Edited on 13-2-2005 by Marvin]
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neutrino
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[*] posted on 13-2-2005 at 09:48


I just realized the error in my reasoning: the thermometer would be way too long for the whole thing to fit into the 3-way adapter. You would need a PI thermometer after all. One more question then: where should the line above the bulb be: where the thermometer meets the rubber adapter (at the top of the 3-way adapter) or where the tube connecting to the condenser meets the tube from the boiling flask?
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[*] posted on 13-2-2005 at 10:17


I suggest a 300mm condenser for distillation, because of commonly distilled low-boiling cpds. Even with ice water going through the condenser, it can't be too long. I use the same for reflux.
Hardware store tubing works fine for vacuum. They also have yellow rubber tubing for the condenser.
I use 3-finger clamps for everything, I've found other clamps too flimsy. And 2 stands.
You also have to consider length of the thermometer, if you use a 3-way adapter you may find the temperature hard to read with a shorter thermometer.
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[*] posted on 13-2-2005 at 11:22


Organic glassware kit: I went with a 19/22 kit from Kontes - a bit expensive but I'm very happy with it. It has all the flasks, a condenser, reflux column, thermometer adapter, claisen head, distilling head, etc, that you need. I've see some real bargains (<$200) on ebay for these kits - but you may not be patient enough to wait for one. :D I don't know why those kits from UGT wouldn't be fine -I believe they are a reputable company.

1. I would go with ground glass RBF - it's proven technology and gives a very quick, painless, set up. I use 2 stands. I use a lab jack to hold up the receiver flask. I use Keck clamps at all joints with a very thin coat of silicone grease at the joints. This will minimize vapor leakage to ambient.

2-4. I have not tried a Vigreux but wished I had one with the acetic acid preparation as I was getting a lot of column flooding. But I understand they are equivalent to only about 2.5 plates so this might not have been adequate. I have some nice Czech glass beads from my local craft shop that I will try next for fractionating.

5. I have a Corning 5" x 7" stirrer/hotplate for general heating and evaporating work. I wouldn't go any smaller.

I debated a long time about how to heat the different sized RBF's. Originally my school used the one-size-fits-all Electrothermal type flask heaters - they were frustrating at times. Then they started using the Glas-Col fiberglass hemispherical mantles ("breast warmers";) and I liked them a lot. You need an independent variable voltage power supply (ebay - $10) for these. So I bought a 500 mL and a 100 mL size mantle, both of which I support with a 500 mL size "extension support" ring (steel w/2 fiberglass cross straps). This system works very well. What I really like about it is that I support it a few inches about the bench using a ring stand. I support the glass independently. Then if I ever need to cut the heat instantly I just drop the mantle and swing to the side! voila! no more heat! When you are venturing into the unknown as we do this can be important. :o

I agree on the 3-fingered supports. The reason I like them is that they are adjustable in place in regard to the clamp distance from the ring stand. The style that don't are a real pain in the ass.

For cheap but good lab equipment you only need to know 2 words: Carolina Biological.




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[*] posted on 13-2-2005 at 11:49


All I can say is it depends what you want to do with kit.

If you are doing higher temp stuff with a condenser with an internal cooling coil, which is very efficient, it has more chance of cracking and the water goes straight into the reaction.

Under vac the glassware needs to be good quality. A good quality water pump will give within 10% of the average high vac pump.

The vigreux column is petty inefficient unless lagged, glass fibre pipe lagging (could cut windows in it to see how things are going). If the column is flooded then there is very little fractionation.
Glass beads or cut up glass tubing seems to work. I used a few bits of larger pieces of tubing to support the column and then added the smaller bits.
The distillation condenser could be used for the reflux condenser.
PTFE tape can be used to make seals.
For basic filtering a good quality aquarium pump seems to work, run in reverse.
For reactions under inert conditions I am going to try the metallised Helium balloons.
mick
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[*] posted on 14-2-2005 at 16:53


Quote:
Originally posted by mick
For basic filtering a good quality aquarium pump seems to work, run in reverse.

For reactions under inert conditions I am going to try the metallised Helium balloons.
mick


Huh? how do you use an aquarium pump for filtering? I just dont get it. Aquarium pump moves water. Filtering relies on Vac. yes/no??? Maybe I'm missing something.

Elaborate a bit on this Helium balloon idea?
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[*] posted on 15-2-2005 at 00:48


You connect the aquarium pump to an aspirator, so that it pumps water through aspirator. Aspirator provides vacuum and is then connected to filtering flask.

The baloon filled with He is placed on a free neck of RB flask and is used as air protection. This is an economical way of using an inert atmosphere, because you don't have to supply He from the cylinder continuously.

[Edited on 15-2-2005 by demorol]
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[*] posted on 15-2-2005 at 05:06


About the balloon idea: make sure you don’t use any of that party-supply store helium, as that usually has a good deal of air in it. This is added so people breathing the stuff (kids) don’t suffocate from a lack of oxygen.
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[*] posted on 15-2-2005 at 18:40


Quote:
Originally posted by neutrino
This is added so people breathing the stuff (kids) don’t suffocate from a lack of oxygen.

And some/most adults :P:D

-rlr
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[*] posted on 16-2-2005 at 15:39


Maybe a bit off-topic but what a friedrich condenser is used for? Also can someone go a bit farther by explaining what are the use of the most common type of condenser?
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[*] posted on 16-2-2005 at 15:56


No, no canadian :P
I know the usual difference between a reflux, Liebig and West. But i just don't see why, how and in which case i should use a Dewar, Friedrich, Graham or Ailhin. Maybe when i'll get my degree in chemistry i'll know that but for the moment I just see some basic difference but not enough to know how to use them adequatly. :)




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neutrino
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[*] posted on 16-2-2005 at 17:16


As far as I know, Allhins are used for reflux (bulbs = higher surface area for heat exchange), Dewars are used for cooling mixes (like dry ice-acetone) which you can’t circulate through the condenser, and Grahams are used for low-boiling vapors, but have to be pointed vertically downward in order to work. Why anyone would use a Friedrich, though, is beyond me.
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Magpie
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[*] posted on 16-2-2005 at 17:33


There is a thread on this. Search under "condensers."



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[*] posted on 17-2-2005 at 14:10


Originally posted by mick
For basic filtering a good quality aquarium pump seems to work, run in reverse.

For reactions under inert conditions I am going to try the metallised Helium balloons.
mick

The basic aquarium pump is a rubber diaphagm with non-return valves, so it will pump and also suck at a low level.

About the He balloons. The metallized balloons have a very low porosity to O2 and N2 unlike rubber balloons. The rubber balloons are only OK for short term stuff.

mick

All advice is always appreciated and never forgotten

Trying to talk with a lung full of He use to be funny.


[Edited on 17-2-2005 by mick]
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Chris The Great
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[*] posted on 23-2-2005 at 19:21


Been pretty busy lately, only been able to quickly check into the forum. Anyway, thank you all so much for the advice! It has helped alot!

I am going to go with a longer liebig condenser, a 400mm, to make sure that it will work with lower bp liquids like ether and for refluxing said low bp liquids. This will go with the distillation setup UGT is selling on ebay instead of the 200mm liebig, hopefully they will let me do that without charging too much extra. I will also pick up a 250mL RB flask to go with this for distilling lesser quantities of stuff.

About the Vigreux column, I have read some more on the issue, which has told me the vigruex is moderatly efficient, but has a high flow rate and works well in a vacuum. Other types of columns, such as using bits of glass have low flow rates and apparently do not work well under vacuum. It is for this reason I will be getting a 400mm vigreux sometime later, when I get more money, for seperating out solvent mixtures, distilling sulfur chlorides and thionyl chloride (to give some examples of the intended usage). Unless of course doing so would be a bad idea, but it seems to be what I need.

By "standard glass tubing" I meant the diameter of the tubing that fits in the general stopper holes. If there is such a thing as a general size for a stopper hole.... I need glass tubing to stick into stoppers, and in rare cases to connect things together such as if I am using SO3 gas (thionyl chloride) which I would be hesistant to put through rubber tubing from my local hardware store.

Now, I've been looking over my many experiment plans to see what else I will need to get after this. So, I ended up with some more questions.

In your experience, would it be better to get a three neck flask, and stopper one of the holes when you need a two neck, or buy a two neck flask and not have to stopper/worry about leaks? I am thinking that a 3 neck flask is probably worth the extra money, but I'm wondering if the people who actually have three neck flasks if they need the three necks, or usually just use two.

Addition funnels seem to be basic, I am looking at a 500mL with teflon valve and pressure equilizing tube (I know that it will be extremely handy, for everything, and worth the extra $).

Claisen adpater, 24/40, nothing special. Just a really handy piece of equipment.

Glass stoppers- these are expensive! Also, do glass stoppers with holes for tubing in them exist? I am having trouble finding any stoppers of any kind, UGT wants $11.50 for one 24/40 stopper, and I haven't seen them anywhere else. I need a few 24/40 glass stoppers and a couple 24/40 glass stoppers with a hole for glass tubing, if they exist (hopefully). Rubber stoppers are a no-no for some of the stuff I will be doing with the appartus, so they will not be suitable for me to use instead of glass stoppers, although I will be picking up a few for other stuff.
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[*] posted on 23-2-2005 at 19:48


A thermometer adapter with a ground glass fitting will work for 6mm glass tubing I would think. In fact I have an experiment planned for tommorrow that will use this technique. I plan to use a 25x200mm test tube positioned horizontally as a reaction vessel for a dry distillation. I will use a rubber stopper with 6mm tube (bent 17 degrees) leading to my condenser that has ground glass fittings. I'm using a test tube instead of an RBF because: (1) Provide more surface area for gas evolution, and (2) if I ruin the test tube I won't cry much - but if I ruin my ground glass Kontes RBF - there I would cry.

[Edited on 24-2-2005 by Magpie]

[Edited on 24-2-2005 by Magpie]




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[*] posted on 24-2-2005 at 09:35


For a stopper with a hole in it, use one of UGT’s thermometer adapters. The glass part has a hole through which tubing could fit, although the one I have (the rubber one) needs the rubber piece to provide a seal. I’m not sure how the nylon one works, but it may be worth a try.
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[*] posted on 24-2-2005 at 10:37


I have the nylon one, it is just a hole in the top, which is actually slightly big for my thermometer so I have to use teflon. However, if you want to distill nitric it might be a good idea.

I ordered all my stuff recently too:

400mm West/leibig Condenser
1000ml Round Boilong Flask
3 Way
Nylon thermometer holder thing (its a little bit for ost thermometers IMO, 7mm IIRC)
Stands + Clamps

Did I forget anything? Also, the little connecter things on the outside of the west/liebig, where the water is supposed to go, what would be a good way to pump it trhough there. i am not sure how well an aquarium pump would work for a large size like 400mm.




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[*] posted on 24-2-2005 at 11:36


The pressure equalizing dropping funnels are expensive and relatively fragile. On a quickfit set up I use screw cap adaptors with inserts cut with a cork borer (or sharpened bit of tubing of the right diameter and a hammer) from PTFE faced silicone rubber (I have found some relatively cheap large reagent bottle top inserts of this) or just silicone rubber. A long double ended syringe needle goes from the top of the dropping funnel to a side arm on the flask. A bit of thin tubing of the right metal could be used, with a bit of a point filed on the end.
With PTFE tube getting cheaper and more available that could be used. The seal can be made from PTFE tape by wrapping it round what ever tubing needs to be sealed (loosely) and compressing it into shape with the screw cap adapter, add a bit more etc. I have made stirrer guides like that using these adapter ( the best are PTFE screw cap adapters, which have run overnight and still had got a good seal from an argon bubbler).
mick
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[*] posted on 24-2-2005 at 22:40


For pumping, there are very cheap fountain pumps at the hardware store. They last a long time. The smallest one should be less than $15.
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[*] posted on 4-3-2005 at 10:00
Heating


Quote:
5: Heating- I'm planning on using a Crockpot (for making stew) to heat an oil bath. Some modifications will be made to the heating controls of course, apparently these can get to 250C without a problem, I assume this will work well for distilling with a small stand for the flask? It also means I can be cheap, as old Crockpot's, oil and a simple stand are dirt cheap.

I noticed magpie listed a stirring hotplate in his inventory but no one has really emphasized this. If you're going to be doing vacuum distallations, you will need a stirring hotplate and magnetic stirbars or you will experience bumping. I use an aluminum pot on top of my stirring hotplate for the oil bath since aluminum does not interfere with the magnetic stirring.
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[*] posted on 6-3-2005 at 02:05
BUCHI


I am looking at buying some of these BUCHI flask they look more of a tear drop shape than round does anyone know if they are any good for vacuum distilling?
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[*] posted on 6-3-2005 at 07:39
Condensers


I have many different styles of condensers in my collection but I still rely on the
liebigs for most applications - even vacuum. The advantages I find with these
condensers is low cost and ease of cleaning. They'll even work as refluxers with
a long coolant jacket and a high rate of coolant flow.




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