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Author: Subject: Lab Fridge. I searched around and Didn't Find Much...
zenosx
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[*] posted on 6-10-2014 at 18:42
Lab Fridge. I searched around and Didn't Find Much...


More and more I am finding a need for a laboratory fridge. However, because of the explosive nature of some compounds, and the "hobby" nature of this site for us, I am unsure of what would potentially be appropriate.

I would potentially at the most be chilling compounds that could develop peroxides like diethyl ether, etc. More likely it would be chilling various biological suspensions that I am currently developing work on. Either way. Any cool environment to prolong the shelf life of compounds is the idea.

What do you guys use for lab fridges? I have been thinking that a standard Mini-Fidge with the built-in freezer might be economically friendly, and close enough to what I have use for. It wouldn't need to be explosion proof, as I really wouldn't trust anything but a professional lab fridge for truly explosive compounds (why I don't synthesize them except on a per use basis..)




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[*] posted on 6-10-2014 at 23:22


Quote: Originally posted by zenosx  


What do you guys use for lab fridges? I have been thinking that a standard Mini-Fidge with the built-in freezer might be economically friendly, and close enough to what I have use for. It wouldn't need to be explosion proof, as I really wouldn't trust anything but a professional lab fridge for truly explosive compounds (why I don't synthesize them except on a per use basis..)


according to vogel ,you need a professional lab fridge(one with a spark-proof compressor) to store even ether:cool:

also sometimes even a lab fridge will not be able to prevent an explosion. i once read on some other forum that the an instructor left diazomethane in the fridge and next day he saw that the door of the fridge was embedded in the wall 20 metres away:D

[Edited on 7-10-2014 by CuReUS]
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[*] posted on 7-10-2014 at 02:59


I also thought about this a few weeks ago. You dont want to store toxic chemicals together with your food. I was thinking that i would buy a mini fridge, but after hearing what Cereus said, i am thinking that a lab fridge would be better.

Where do you find a lab fridge, and whats the price for a small one, approx?
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[*] posted on 7-10-2014 at 05:16


If you live somewhere so hot that you have to store ether in the fridge, perhaps you should think about finding alternatives to use instead which are more suited to your climate.

[Edited on 7-10-2014 by forgottenpassword]
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[*] posted on 7-10-2014 at 05:18


I am interested in one as well. I have looked around, and being aware of the exposed windings and such on the compressor, etc., I wasn't willing to use just any fridge. The lab fridges I found online are quite a expensive, and not something available to the average home amateur.

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[*] posted on 7-10-2014 at 06:28


Quote: Originally posted by forgottenpassword  
If you live somewhere so hot that you have to store ether in the fridge, perhaps you should think about finding alternatives to use instead which are more suited to your climate.

[Edited on 7-10-2014 by forgottenpassword]


I store dichloromethane, as a low BP, non-combustible replacement for diethyl ether, and petroleum ether in a garage fridge.

I use n-heptane (Bestine, available from art suppliers by the quart and gallon, BP 98 C, but still pretty volatile) when I really need the strictly non-polar properties of petroleum ether.
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[*] posted on 7-10-2014 at 14:04


An amateur 'Lab Fridge' is sold commercially as a Fridge.

You just put it in your Lab, rather than the Kitchen.

That makes it a Lab Fridge.




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[*] posted on 7-10-2014 at 16:53


You can use a normal fridge for the storage of most non-flammable chemicals without any issues. And storing highly sensitive explosives like diazomethane is probably a less than good idea regardless of what type of fridge you own.

If you want to store flammables safely, then you can still use a normal fridge, with some limitations. You need to make sure that there are no ignition sources inside the fridge. That means, remove the light socket, any thermostats which switch internally, and so forth. These things can be removed from a regular fridge or replaced with external equivalents, if you know what you're doing (or know someone who does!).

One thing to think about, however, is corrosives. The cooling coils are usually made of aluminium these days, and do not like even the tiniest traces of acid in the atmosphere. If the coils are exposed and you have corrosives in there, you will walk in one day and find the fridge running with no coolant (trust me, I speak from experience... one very well sealed bottle of thionyl chloride was enough to ruin the coils in a six month old, $1500 kitchen-type fridge we used in our university lab!). I suspect that you could coat them with epoxy or something resistant, but I don't know how well that would work. Of course, in a home lab, you may well not have any corrosives you want/need to store cold anyway.
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[*] posted on 7-10-2014 at 20:26


I have a full size extra refrigerator that I picked up on craigslist for chemical storage in my garage. I store solvents in the freezer at 8F and the rest of the chemicals in the main refrigerator at 40F. I don't store dangerous chemicals like alkali metals and sodium azide or oxidizers; they get stored in a different location. The problem with a refrigerator in the garage is that during winter in the Midwest I need to remove some of the chemicals back in the house for the winter.



[Edited on 8-10-2014 by jamit]
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[*] posted on 7-10-2014 at 20:33


I store my solvents and bromine in an outdoor shed. They are subject to cold winters and hot summers but this has caused no problems. The only thing I store in a fridge is 35% H2O2 which is kept in my kitchen.

Storing ether in a fridge with food is a very bad idea. I found this out the hard way. Any item that contained fat, like ice cream and meat, became tainted and had to be thrown away.




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[*] posted on 7-10-2014 at 23:34


Quote: Originally posted by Magpie  


Storing ether in a fridge with food is a very bad idea. I found this out the hard way. Any item that contained fat, like ice cream and meat, became tainted and had to be thrown away.


what does ether do when it comes in contact with fats ?:o
could that reaction be of any synthetic importance(to make protecting groups?)
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[*] posted on 7-10-2014 at 23:46


Quote: Originally posted by CuReUS  

what does ether do when it comes in contact with fats ?:o
could that reaction be of any synthetic importance(to make protecting groups?)


Usually the phase is liquid and it extracts fats, but since Magpie is talking vapors here, he does literarily mean it tainted, or contaminated his food. It is possible to use ethers as protecting groups for alcohols, or even special ether-like ketal/acetal groups on ketone and aldehyde respectively... but this is the formation of an ether, not the use of one.


Ether lipids (of glycerol) are biological signaling and structural molecules, and the synthesis of them would require etherification of specific glyceride chains, so that could be viewed as a use in the synthesis of these compounds, in some manner of thinking.
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[*] posted on 7-10-2014 at 23:53


Quote: Originally posted by ziqquratu  
You can use a normal fridge for the storage of most non-flammable chemicals without any issues. And storing highly sensitive explosives like diazomethane is probably a less than good idea regardless of what type of fridge you own.


but because of its explosive nature,no one will ship it to you(it might blow up during transportation:D ) ,and synthesizing it is a pain(you need to use a special distillation kit from Sigma-aldrich because diazomethane can explode if you use normal ground glass joints;) so chemists make it in big batches once and for all and store it in the frigde

and you cant deny the fact that it is the best alkylating agent around:D

Quote:
If you want to store flammables safely, then you can still use a normal fridge, with some limitations. You need to make sure that there are no ignition sources inside the fridge. That means, remove the light socket, any thermostats which switch internally, and so forth. These things can be removed from a regular fridge or replaced with external equivalents, if you know what you're doing (or know someone who does!).

in today's fridge,the defrosting is automatic,which means the compressor "switches" on and off every 12 hours.now you cant take the compressor out,can you;)

so you would have to buy a fridge with manual defrost,and every time you defrost it,you have to take out all the chemicals.finding such a fridge with and age old technology in today's world can be challenging:cool:

Quote:
The cooling coils are usually made of aluminium these days.... I suspect that you could coat them with epoxy or something resistant, but I don't know how well that would work.
the coils act as a heat sink.what that means is that the coolant absorbs heat from whatever you store in the fridge,dumps it into the heat sink and in the process becomes cooler so that it can absorb heat again and the cycle can be repeated.the heat sink in turn dumps it into the atmosphere and it has to do that fast,or you might just wait for winter to keep things cool ;) .hence a good conductor like aluminium,before they used copper but copper is expensive and will increase the weight of the fridge(copper is more dense that aluminum,thats why overhead cables and high tension wires are made of aluminum

covering it with epoxy will decrease its ability to lose the heat to the atmosphere
but wont the aluminum be already covered with an oxide layer,and isnt that oxide layer resistant to even conc nitric acid(thats why nitric acid is transported in aluminum tanks)

[Edited on 8-10-2014 by CuReUS]
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[*] posted on 7-10-2014 at 23:59


Quote: Originally posted by Chemosynthesis  
Quote: Originally posted by CuReUS  

what does ether do when it comes in contact with fats ?:o
could that reaction be of any synthetic importance(to make protecting groups?)


Usually the phase is liquid and it extracts fats, but since Magpie is talking vapors here, he does literarily mean it tainted, or contaminated his food..


so does that mean that magpie kept the ether in the fridge one night and the next morning he saw that all the fatty foods had become emulsions?:D
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[*] posted on 8-10-2014 at 00:04


Just use peltier cells! double them up for better performance, you can get them really cheap on ebay. My little polystyrene fridge box with 6 cells is around 1c most the time, all you need is a difference in temperature.
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[*] posted on 8-10-2014 at 00:05


Quote: Originally posted by CuReUS  


so does that mean that magpie kept the ether in the fridge one night and the next morning he saw that all the fatty foods had become emulsions?:D


Probably more comforting and interesting than the unpalatable surprise I suspect he had.

[Edited on 8-10-2014 by Chemosynthesis]
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[*] posted on 8-10-2014 at 00:21


Quote: Originally posted by Little_Ghost_again  
Just use peltier cells! double them up for better performance, you can get them really cheap on ebay. My little polystyrene fridge box with 6 cells is around 1c most the time, all you need is a difference in temperature.


i thought that a difference in temperature would produce an electric current according to the seebeck effect

to do the opposite i.e the peltier effect ,you would have to pass current through it .which will make one junction(or one side as in the peltier cell) hot and the other junction cold

generally peltier cells are used in biolight camping stoves

in these stoves ,one side is exposed to the heat from the fire whereas the other side is exposed to the atmosphere(in this case the cool night air;) ) .this will produce a current which can be used to charge your phone etc

but is this an efficient solution .the size of the fridge will be really small(i have heard they make portable frigdes with this idea)
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[*] posted on 8-10-2014 at 12:05


Quote: Originally posted by CuReUS  
Quote: Originally posted by Little_Ghost_again  
Just use peltier cells! double them up for better performance, you can get them really cheap on ebay. My little polystyrene fridge box with 6 cells is around 1c most the time, all you need is a difference in temperature.


i thought that a difference in temperature would produce an electric current according to the seebeck effect

to do the opposite i.e the peltier effect ,you would have to pass current through it .which will make one junction(or one side as in the peltier cell) hot and the other junction cold

generally peltier cells are used in biolight camping stoves

in these stoves ,one side is exposed to the heat from the fire whereas the other side is exposed to the atmosphere(in this case the cool night air;) ) .this will produce a current which can be used to charge your phone etc

but is this an efficient solution .the size of the fridge will be really small(i have heard they make portable frigdes with this idea)


Yes your correct, however if you put the hot side inside the fridge and the cold side of that outside the fridge and backing onto the hot side of the other, then you put a cpu aluminium heatsink on that, wire a 35mA (or less) cpu fan (you can find them at the dump but dont use ones over about 35mA.
Then what happens is the cell pulls hot air from inside the fridge to the outside, this produces a current as you say, but if you have them back to back and a temp difference then normally you can get the fridgee pretty cold if you use the wrong side in the fridge, sometimes the fan will cycle alot but that dosnt matter. what matters more is you draw off and use the current hence the heatsink and fan.
Works a treat, I also use this sort of thing on my fishtank LED lights, it keeps them cool and powers the fan.
It dosnt work if you put the cold side in the fridge though, in you do that then you need to power it, you also cant (I dont think anyway) get below about 1C

[Edited on 8-10-2014 by Little_Ghost_again]
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[*] posted on 8-10-2014 at 12:47


The Peltier effect, simply put, is that if you pass a current through a Peltier device, the Heat transfers from one side to another.

Often referred to as a 'Peltier Heat Pump', as it basically pumps the heat from one side to the other.

They are really Cool devices.
Oh, and Hot too, on the other side.




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[*] posted on 8-10-2014 at 13:19


Quote: Originally posted by aga  
The Peltier effect, simply put, is that if you pass a current through a Peltier device, the Heat transfers from one side to another.

Often referred to as a 'Peltier Heat Pump', as it basically pumps the heat from one side to the other.

They are really Cool devices.
Oh, and Hot too, on the other side.

You dont have to pass a current though, if you use them back to front then they make a current. place your hand on the cold side and you can light a led, use a linear technology dooh dah and you can up the voltage output and power a fair bit.
Weurth elektronica do a cool kit for energy harvesting, we have one at school
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[*] posted on 8-10-2014 at 16:04


I don't "Need" to store ether in the fridge as my lab stays pretty well at 20C, I was thinking more of lowering vapor pressure n such, i suppose it isn't really necessary. Having one just for chemicals would be ideal as I will not mix chemistry and cooking :)

On the manual defrost, my current (old) mini fridge upstairs is exactly like that. I have to unplug and defrost it manually. Maybe I'll use it and buy a new one for the upstairs.

Thanks for all of the very helpful replies. I learned quite a bit that I didn't know.




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[*] posted on 8-10-2014 at 20:49


Quote: Originally posted by Little_Ghost_again  

You dont have to pass a current though, if you use them back to front then they make a current. place your hand on the cold side and you can light a led, use a linear technology dooh dah and you can up the voltage output and power a fair bit.
Weurth elektronica do a cool kit for energy harvesting, we have one at school


Little_Ghost you seem to be implying that your fridge requires no power source, which I find impossible to believe given those pesky laws of thermodynamics. Do you think you could post a diagram so we could better understand what you are talking about?

[Edited on 10-10-2014 by Polverone]
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[*] posted on 9-10-2014 at 08:20


i think what he is trying to say is this
let one peltier cell be represented like this- [c||h] (actually the formation of cold and hot side depends on the direction of the current ,which depends on how you connect the terminals of the peltier cell with the terminal of a battery)

now suppose two cells are kept side by side ,the cold side of one cell inside the fridge,the hot side of the first cell facing the hot side of second cell and the cold side facing the fan

fridge -c||h-h||c -fan

now initially there is no hot or cold side
when the fan is switched on the two junctions are created in the right cell
due to this a currect flows in that
that current flows to the second cell and makes two junctions
but isnt it easier to just connect the peltier cell to the external power source
and wont the cpu fan cause sparks if the connections get corroded:o
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[*] posted on 9-10-2014 at 10:50


No I didnt explain well.
In the weurth kit there is a cell connected to a circuit to boost the current etc so it runs a micro board and LCD.
The hot side of the cell is connected to heat sink of largeish size, the side that feels a bit cooler is the side you place your hand or whatever. Now this side drags the heat from your hand to the other side of the plates ~9they are just N and P type junction plates, this produces a current and the micro and LCD light up.
So I took this further, Iput the side that got warmer to another plate, this warmer side is sandwiched with the side that feels slightly cooler on this second plate, this drags the heat out quicker from the first cell. The heat sink now goes on the warm side of the second cell so it can rid itself of heat.
They work by temperature gradients so the warmer of the two sides must have a large ish heat sink. the more heat you can shed from the warm side the cooler the cold side gets.
its not magic just thermodynamics, or basically a heat pump!
The fan just helps use the current and give the cells two sides, they come with a red and black lead, although you can wire any way around stick to the red and black and dont put in serise.
To get it going properly you warm the side inside the fridge to create a temperature gradient.
It does eventualy equal out and stop making a current, but in use I havnt seen this.
With heat from say fish tank lights the cells will produce plenty of current as long as tere is heat.
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[*] posted on 9-10-2014 at 10:53


Forgot to add that as long as the room the fridge is in is at least 8c warmer than inside the fridge it works fine, if your room is say 3c then it isnt going to work very well, if you heated the room to 60c you would get a freezer :D
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