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Drying IPA with silica gel ? Will this work ?

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Ian.M:
Probably the best idea is to determine how much water it has adsorbed over the years so you know what you are working with, then use it for applications that concentration is suitable for, and also as Mechatrommer suggested, get a smaller quantity of high purity IPA, appropriate to your usage rate, for when you need the 'good stuff'.

To determine the concentration, get the room and solution temperatures as close as you reasonably can to 20 deg C, and either use a hyrometer, or weigh a litre on accurate scales (check against a litre of  water) to determine its specific gravity (density) then look it up in this table: http://www.pharmcoaaper.com/pages/TechLibrary/tech_docs_high_purity_solvents_reagent_chem/specific_gravity_isopropyl_alcohol_water_mix.pdf

BravoV:

--- Quote from: Mechatrommer on July 02, 2019, 11:01:31 am ---.... doubt the purity of cheaper 30 litres compared to more decent priced 1 or 2 litre chemicals.

--- End quote ---

Well, the 30 litres I bought is Merck brand made in German, and it came with factory seal, bought them from a surplus from a big chemical surplus shop that sourced from a big chemical factory that was closed. Pretty confident it's quality is much better than those cheap no brand even has the same concentration.



--- Quote from: rikkitikkitavi on July 02, 2019, 12:49:12 pm ---BravoF, if your IPA doesnt leave any residue but slowly evaporating water then it should not be  a problem.

High purity , i e low water content IPA is best used for non polar polutants, and follow up by a rinse with demineralised water will clean up your PCBs nicely.

--- End quote ---

Mine has almost undetectable dry residues (by eyes) when the IPA and water have evaporated.

As I used it to clean my camera's lenses too, this method is easy to spot on the purity. I did try compare the Merck brand vs other cheap no brand one I bought once, put a droplet each at a very clean glass surface like camera lens, then let it dry in open air. The Merck brand didn't leave any visible residue mark at all, while the no brand one left a very-very faint circle on the dried droplet but noticeable when dried. This method is easier to spot at camera lens or glass lens as they have the faint colored shaded coating at it's reflection.



--- Quote from: Ian.M on July 02, 2019, 12:58:35 pm ---Probably the best idea is to determine how much water it has adsorbed over the years so you know what you are working with, then use it for applications that concentration is suitable for, and also as Mechatrommer suggested, get a smaller quantity of high purity IPA, appropriate to your usage rate, for when you need the 'good stuff'.

To determine the concentration, get the room and solution temperatures as close as you reasonably can to 20 deg C, and either use a hyrometer, or weigh a litre on accurate scales (check against a litre of  water) to determine its specific gravity (density) then look it up in this table: http://www.pharmcoaaper.com/pages/TechLibrary/tech_docs_high_purity_solvents_reagent_chem/specific_gravity_isopropyl_alcohol_water_mix.pdf

--- End quote ---

Thanks, noted, but I've decided its not worth the effort as I was just trying to find an easy & cheap to dry it, not interested if its troublesome, guess I have to live with it for now.

rikkitikkitavi:
Well, leave no trace, that is the purpose of the solvent.

If you need to remove something very greasy, ie non polar fat IPA is not the best to begin with anyhow.

But for cleaning PCbs and electronics is the best.

You keep your IPA.
30 liters will get you far.

And when you don't want it anymore, add some hand washing agent, blue colour and dilute with water and use it as wind screen cleaner :)

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