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Author: Subject: Copper sulphate and vacuum question
NEMO-Chemistry
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[*] posted on 13-1-2018 at 09:11
Copper sulphate and vacuum question


I have two VAC pumps, one is really old. Its the type that used to have a glass bell jar on top of the Vac inlet, it has a separate motor belt connected to the vac unit.
I use this for most my dirty vac work, but the spare seals and gaskets are getting harder and harder to get. So i feel like i need to abuse it less.

The other pump is my good one, its a two stage one that sucks like a ' ', well put it this way, it could suck a water melon through a hose pipe.

This pump i normally use with a vacuum chamber, various traps etc and change the oil frequently. the last stage of the line to the pump normally has a wash bottle, in this i put a mix of mineral and veg oil with a emulsifier in.

My hope is this catches at least some the water.

Normally if i put a beaker of cold water (1-2c), in the vac chamber in my cold lab, the pump pulls a vac good enough to boil the water within 15-20 seconds.

So I decided to dry some finely powdered copper sulphate with it, the copper sulphate was anhydrous a month or two back, but over the last few weeks the colour has become more blue as it has picked up water from the damp air.

The powder is normally sealed up, so its not alot of water. Anyway, i put the powder in a thin layer in a beaker and pulled a full vac. I ran the pump for a good 30 mins, after 30mins i couldnt detect a single change in colour!!

I was so sure the pump would pull the water out the copper sulphate! So this has given me an idea.....

My pump is either fecked (no gauge on it), or copper sulphate at a cold room temp dosnt want to give up water easily, if this is the case then maybe i could put anhydrous copper sulphate in the last wash train sandwiched between some filter paper, draw the air through the powder and into the pump.

Given all the above, do you think this would work?
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Reboot
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[*] posted on 15-1-2018 at 17:50


I assume it just doesn't want to give up the water. Perhaps it would in time. Normally I would just say to use something cheaper like magnesium sulfate, but of course copper sulfate opens up the possibility of changing color as it becomes saturated with water.

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[*] posted on 15-1-2018 at 17:58


There is a difference between water in a damp portion of a substance and water of crystallization. I would not expect a vacuum to remove water of crystallization.
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[*] posted on 16-1-2018 at 04:08


Thats a shame. It makes sense when i think about it, the water needs alot of energy when removing from a crystal, so copper sulphate taking up water is not the same as forming a crystal and trapping water.

Or in short...

I am talking bollocks and it wont trap water! Shame though as it would have been an excellent and cheap way to protect the pump, back to the cheap skate methods i use.
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