DanteDominic
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Leaking Unions
Hello everyone, I'm new here and wanted to say thanks first off!
I'm newer and been having some issues with unions leaking. I've started with simple distillation of water just to make sure I'm getting everything
correct and I know what I'm doing. I don't want sulfuric acid or anything leaking all over the counter or vapors fuming into the space.
I have noticed though that at times I don't get the yield I would like. at first I noticed leaking coming from one union, but after patching that up I
noticed it coming from the other as well. searches online said to use plumbers Teflon tape but I'm not entirely sure how that might hold up later on,
or if it could effect or potentially destroy a solution in the future.
I'm currently using it, I've not tried a new distillation with it on both unions so perhaps I'm coming here a "bit" premature. but I did want to pick
the brain of the experienced a bit to see what everyone thought about "Teflon tape." if that makes sense.
I'm not entirely sure if the issue lies in the glassware I bought, I'm sure its not the best but I am just starting out. I got Stonylab from amazon...
don't throw me to the wolves just yet. if you can recommend any better glassware that isn't going to break me, I would appreciate it.
Thanks in advance!
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Radiums Lab
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Hi welcome to SM, I'm also new here.
Can you please tell what distillation are you performing and what lubricant you are using for the unions?
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Radiums Lab
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If ur performing high temp. distillations teflon tape is a bad option because it will melt and spoil ur product and glassware.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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DanteDominic
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Hi Radiums!
I'm not using any lubricant, should I be? I tried Vaseline at one point but it wasn't working. also I'm doing low temp? I've been rocking around
75-80c.
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BromicAcid
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Teflon tape can work, and the upper processing limit is very high, around 250°C before it starts to break down. That being said plumbers tape in the
store sometimes has other 'inert' fillers so you need to be careful of the brand. It's also hard to get a good seal, if you're doing vacuum work that
could be important. They do sell solid Teflon sleeves that can be reused hundreds of times though if you were inclined to find the right tool for the
job.
Your best bet is to get some actual vacuum grease, lots of sellers on amazon shifting the stuff somewhat affordable, go for the Dow Corning stuff.
This will help 'hold' the joints together. You grease the male side and push together and twist till the joint is transparent. Vasaline is just too
thin and thins out too much on heating to be very good for this.
Please try not to work with with dry joints, this makes them much more susceptible to freezing where they get stuck together. Vacuum grease during
assembly, wipe clean with a paper towel after assembly and if you've got the money for some acetone wipe them off against with an acetone damp paper
towel. You don't need a ton of grease, but you don't want to starve the joint, I suppose finding the right middle ground could be an art but I don't
think about it much anymore - if you have too much grease it could contaminate your product.
Your other problem like you said is the joints coming apart. Part of this is probably due to your setup, you want to assemble so you don't have
tension on the glassware, it should all be supported from the bottom with clamps to hold it from falling forward or backwards. My first clamp stand
was just a blow gun that had been put into a drilled hole in a 2x4. Another thing that could help are some Keck clamps, after the invasion of Chinese
knockoffs you can pick up something claiming to be a Keck Clamp dirt cheap online. They just slip over the joints and apply some pressure keeping
them together. If you have a 3D printer someone on our forum did some work making a model and testing them out.
Good decision to give things a try with water first, helps with a lot of the nuances like positioning of the distillation probe, and as you've found
out assembling without tension and such.
Best of luck!
[Edited on 4/13/2025 by BromicAcid]
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Radiums Lab
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Can you please tell what you are trying to synthesized or distill
so that someone could suggest lubricant, for some chemicals specific lubes are not a good pair.
For temp. you mentioned teflon is a good sealent but not the best because it too has some tiny gaps for gas to escape so you need to use gel based or
liquid ones.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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DanteDominic
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Hey everyone, thanks so much for all the answers! for now Radiums, I'm just distilling water, I'm trying to figure out how to set things up, fix
leaks, and make sure I fully understand how the pressure will effect things. also how often to top up the water bath, and how to wrap the water bath,
also how that will effect distillation. because I've wrapped the bath in aluminum before and it does seem to help with the distillation and make the
evaporation in the water bath go slower.
I do use clamps for unions. so right now its, teflon tape, and a clamp. I have 2 stands, one holding the flask coming out of the water bath and
another holding the flask where the water is distilling into. I'm using low heat right now because 1. I'm really curious how low you can go to still
get distillate and how that will effect the purity of something. and 2. I can't be here to monitor all the time so I being able to check on it after
work and in the morning is something that is preferred. not that I'll always do it this way but it does help for now.
I've also bought some pool anti-algae and add a tiny bit (diluted in 8oz of water) so that the water bath wont get funky.
I am curious how you might remove some mineral build up because I started using tap water and later found I should be using distilled or deionized. so
if there is a nice way to get rid of some of the buildup inside the water bath I would like to.  something easier than elbow grease because it REALLY seems like it doesn't want to come off, HA!
thanks again for all the help!
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BromicAcid
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To remove mineral buildup you might want to give vinegar a go. It's what most people use to clean the scale out of their coffee pots.
Also as an aside if you're using a water bath they sell plastic floating balls that you can drop in there and they'll cover the surface and insulate
it. Kinda cool but then again water is cheap. For lower temps I've used styrofoam pellets.
[Edited on 4/15/2025 by BromicAcid]
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Sulaiman
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I have some Quickfit glassware and some cheap Chinese glassware,
The main difference is the quality of the ground joints
The cheaper joints tend to be imperfect,
so for Quickfit a tiny smear of grease seals the joint,
cheaper joints require a lot of grease to seal them,
so much that when it heats up during a distillation it can dribble out of the joint
- into whatever it is that you are distilling.
I now use two turns of plumbers ptfe tape instead of grease.
+1 for the vinegar,, almost ay acid will dissolve the deposits from tap water.
Water baths are useful,
but I prefer oil (cooking, lubricating.....) because it does not steam everything up.
It is messier to clean up afterwards though.
Glass is a surprisingly poor conductor of heat,
so when you want to distill a liquid,
the outside of the flask needs to be 50oC or more above the boiling point to get heat through the glass quickly enough to get a decent
production rate.
So for example, to distill water I might use an OIL bath at about 150oC.
CAUTION : Hobby Chemist, not Professional or even Amateur
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teodor
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Quote: Originally posted by DanteDominic  | I'm really curious how low you can go to still get distillate and how that will effect the purity of something
....
I am curious how you might remove some mineral build up because I started using tap water and later found I should be using distilled or deionized. so
if there is a nice way to get rid of some of the buildup inside the water bath I would like to.
thanks again for all the help! |
You can go as lower as you want but for keeping the speed of distillation reasonable you need to do it around the boiling point. Some compounds have
tendency of overheating. The classic remedy for this is putting some pieces of ceramics with rough surface which would serve the purpose of bubbles
nucleation.
There are also chemical methods, they are better. For example, for distilling organic acids you can add some CaCO3 which normally doesn't react with
them except in micro-quantities but that would be enough to achive a smooth boiling just around the boiling point.
I check water purity by measuring it's conductivity. But it shows only compounds which are ionized in water and on the level less than dissolved CO2.
For organic substances adding KMnO4 is necessary. But some gases (NH3) requires a special treatment.
The methods of getting water of high purity is an area of my interests. I have some books regarding the methods. Without very pure water some of
experiments I plan would be impossible to make.
So, if you remove organics and gases the rest you have goes by water/air mist during the distillation - a high vertical column probably can lower the
amount but several distillations (usually 2 is the standard for tap or rain water) are more effective to get rid of inorganics. And then you get the
level when what you have is coming from glassware itself. There is some extra-pure glass but I believe some metals or plastic would serve the purpose
better. But if you need such a purity.
And to answer your second question, the Procter & Gamble company at WW2 time hired few best chemists and they found a solution to add a bit sodium
hexametaphosphate which prevents the buildup. They sell a lot of this simple chemical by the commercial name "Calgon" and it looks like it works
great.
Acids can remove many types of buildup but not all. Sulfates will not go easily. If you didn't use Calgon to keep them in the solution you can also
try it or citric acid to remove them after.
[Edited on 15-4-2025 by teodor]
[Edited on 15-4-2025 by teodor]
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DanteDominic
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hey everyone thank you so much for all the answers. I'm going to try a lot of this stuff.
I suppose the only question I would have left is, if I were to upgrade from stonylab equipment and actually put some money into some QUALITY
glassware, what would I get? also, could anyone recommend a good water bath and heating mantle? right now I'm using joanlab but I've noticed that my
mantle is starting to get weird, it seems like it will drop in temp out of nowhere and then go up again. I thought it might be my variac at first but
I'm not 100%.
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Sulaiman
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| Quote: Originally posted by DanteDominic | | ...I've noticed that my mantle is starting to get weird, it seems like it will drop in temp out of nowhere and then go up again. I thought it might be
my variac at first but I'm not 100%. |
Why are you using a variac?
If you reduce the supply voltage to the heating mantle there is a high probability of 'misbehaviour'
The electronics inside need a minimum supply voltage.
Why not use the mantle's own temperature controller without the variac ?
Personally, if your mantle does not have stirring,
and you have a variac,
I would connect the variac output directly to the heating element,
bypassing all of the internal circuitry.
This would give smooth repeatable control of truly constant heating power.
Really useful for fractional distillation.
CAUTION : Hobby Chemist, not Professional or even Amateur
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Deathunter88
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| Quote: Originally posted by Sulaiman | | Quote: Originally posted by DanteDominic | | ...I've noticed that my mantle is starting to get weird, it seems like it will drop in temp out of nowhere and then go up again. I thought it might be
my variac at first but I'm not 100%. |
Why are you using a variac?
If you reduce the supply voltage to the heating mantle there is a high probability of 'misbehaviour'
The electronics inside need a minimum supply voltage.
Why not use the mantle's own temperature controller without the variac ?
Personally, if your mantle does not have stirring,
and you have a variac,
I would connect the variac output directly to the heating element,
bypassing all of the internal circuitry.
This would give smooth repeatable control of truly constant heating power.
Really useful for fractional distillation. |
He probably has the style of heating mantle where a variac acts as the control (see https://www.orgchemboulder.com/Technique/Equipment/Community...)
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bnull
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I don't think so. Joanlab only sells (as far as I could find) heating mantles that don't need a variac. Heating control is fully electronic (the
simplest would be a triac biased by a potentiometer, the cheapest probably something built around an IC), like the other heaters that have popped up
here. Using a variac with that type is (for the lack of a better word) wrong.
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Cathoderay
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DanteDominic, wait a minute.
You said something about checking it before and after work. At your stage of doing things it is dangerous to operate things like heating equipment
while you are not there. You would need a lot of monitoring and safety equipment I doubt you have. Are you running cooling water all day?
It also sounds like you intend to distill water very slowly, that may not be a good idea with the type of equipment you are using. You are using a
water bath and trying to distill water, the bath will evaporate before the water in the flask.
It may help if you are more specific about your equipment. What model of mantle? If the distillation setup was a kit, which one is it?
The brand is less important than the other details. What capacity boiling flask? How long is the condenser? How big is the receiving flask? What size
joints?
I have a feeling there is something not set up correctly.
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DanteDominic
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I read online that if you're running high voltage of any kind you should use a variac to make sure it doesn't start a fire. so I'm running it in
between the water bath/mantle and outlet. when I'm running the mantle I'm home and I monitor it, the water bath is very low heat. I top it up in the
morning and when I get home from work to ensure the level doesn't get too low. I monitor like crazy and have cameras at home so I can check it during
work as well. also I make sure to set the variac to 120v. it doesn't really move off of it to be honest. it's a fairly decent one. The mantle I have
does have stirring, although I haven't used it. I'm really just trying to get the hang of things and make sure that what I'm doing is working
correctly. no leaks, I'm familiar with the equipment, and I feel comfortable moving onto something more complicated. also this allows me to see if
there are any holes in the tools and equipment that I own. if I come across a problem and need something now, vs in the future when I might be doing
something more difficult. and what I should look for, etc. I like to be prepared before I move on or do anything more complex.
Heating Mantle: JoanLab B07Z4FJFXL
Water Bath: JoanLab B07WZSBRJR
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Cathoderay
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There is some confusion, I think those are the serial numbers. The heating mantles have model numbers that start with H, the water baths have model
numbers that start with W.
Wherever you saw that statement about variacs online perhaps was out of context. A particular situation that does not universally apply. Variacs are
not really safety devices. The same power (volts X amps) that goes in also comes out. If there is enough power going in to start a fire there is also
that much coming out. (neglecting efficiency). A variac does not prevent you getting shocked either. The mantle was designed to be directly plugged
into the outlet (unless it does not contain it's own temperature control), use it as intended.
Have you seen this video?
https://www.youtube.com/watch?v=cw-Wc_KjHgc
Teflon tape should be OK to use as long as the temperature is below about 250 C.
If you use grease it has to be high temperature like silicone based.
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bnull
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| Quote: | | so I'm running it in between the water bath/mantle and outlet. [...] also I make sure to set the variac to 120v. it doesn't really move off of it to
be honest. it's a fairly decent one. |
Now I've got it: you're using the variac to keep voltage around 120 V, right? You're not lowering the voltage to control the temperature.
You don't need a variac. A variac is more appropriate in those cases where you need a soft start, such as an old tube radio or amp, or are using a
simple heating mantle without temperature control, such as those in @Deathunter88's link. What you need is a sort of circuit breaker
or fuse-based thing [ground fault interrupter is one of them] that cuts off power if the mantle/bath malfunctions (short-circuit, mostly).
You also don't need a fixed voltage because: (1) the temperature control of the mantle is based on the readings of an internal temperature probe and
not in the current that flows through the heating element, so as long as the voltage is within acceptable limits (it is probably written somewhere in
the manual, something like 110-130 V) it will run safely; (2) the stirrer has its own voltage regulator.
| Quote: | | The mantle I have does have stirring, although I haven't used it. |
If we're to believe the reviews for that model on Amazon, the heater is good but the stirrer is very fond of malfunctioning. You can fix it if it
breaks, of course.
Edit: I take forever to write, I guess.
[Edited on 18-4-2025 by bnull]
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Cathoderay
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I figured out that those numbers are Amazon item identifiers.
So you have a model HMSC500 mantle (500ml, 250W, with temperature probe) and a model BHS-1 water bath (3L, 300W).
I don't quite understand why you have both. Are you using the water bath for distillation?
So with that mantle you need to always use at least a two necked boiling flask, one neck for the temperature probe, the other the outlet.
Most of the time it seems that the vapor temperature at the flask outlet is the more important one so you would need a temperature sensor or
thermometer there.
I suppose what kinds of glassware (not the brand) you are making the distillation set up out of is an important factor. Which pieces?
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jackchem2001
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For what it's worth I have been pretty unimpressed by Teflon sleeves. Maybe it is because I am using cheap Deschem glassware but I noticed these
problems:
They absolutely cannot be heated. They become stuck on the male joint (even once cooled) and are very hard to remove. One of my stoppers is
permanently a Teflon stopper after one experiment 
Also, when heated any unclamped stoppers can't act as pressure releases (I tried to pull out two different stoppers while hot and it was
impossible).
So I only use them on the receiving side of the apparatus to avoid grease contamination.
On the subject of grease I have some thoughts:
People talk a lot about the perflorinated stuff but silicone grease is pretty excellent and can even be in contact with food! Grease gets
absolutely everywhere so I would rather use something non-toxic.
At least with silicone grease, acetone is pretty useless. You should first wipe with a paper towel and then use a hydrocarbon solvent. This will
remove most grease, however...
... there is always some residue. Fresh ground glass is wetted by water. However, joints that have previously been greased are hydrophobic (even
if they have the characteristic ground-glass appearance). This is another reason why I prefer something benign. A base bath restores the wettability
of the joint.
There are some experiments where silicone grease will not do. For example, chlorine gas will react and form a thick, white, and difficult to remove
residue. In this situation, sulfuric acid is often used but sulfuric acid is a pretty bad grease. It flows and this is a very big problem on
near-horizontal joints (i.e. a distillation head - though this is always a hot spot for leaks even with silicone grease). It also absorbs water which
seems to make it lose its greasing ability - a problem if you build an apparatus on one day and use it on the next.
Also, it cannot be used to grease reaction vessels with boiling water as the water wicks into the joint and dissolves out the grease, eventually
popping the joint. You might expect this to be a problem with silicone grease and say boiling toluene but I have never observed this with silicone
grease.
One final thing - if you don't want grease/sulfuric acid contamination just use a bit of water! If you apply heating then I strongly recommend
disassembling the apparatus while hot (obviously this has to be safe if you choose to use water as your grease).
[Edited on 19-4-2025 by jackchem2001]
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Cathoderay
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The only time I've heard of sulfuric acid used on joints is when distilling concentrated sulfuric acid. Understandable nothing else is likely to
withstand it.
jackchem2001, I am surprised to hear of your problems with Teflon sleeves. I've never used them. Tape seems to work for me but I don't do anything at
very high temperature.
Telfon can flow. Are you using clamps?
Are you doing vacuum distillation?
Atmospheric pressure might be adding force on the joint.
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jackchem2001
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Yes, I think the unfortunate molding/flow effect I observed is due to temperature. In the experiment (atmospheric distillation at around 100 degrees
for a few hours) I didn't use any clamps.
When you are able to, try remove a hot stopper that has Teflon tape in the joint. I assume that it will be difficult to remove and this is bad because
the stopper can't function as a pressure release. With literally anything but Teflon (water, sulfuric acid, silicone, etc) it is easy to remove.
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DanteDominic
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Wow all these answers are outstanding! Sorry that I haven’t posted in some time. I’m going to unhook the cardiac and see how it does.
Can anyone recommend a good heating mantle with temperature control that doesn’t have a probe? I hate that thing and wish I didn’t have to deal
with it, ha!
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