Sciencemadness Discussion Board

Drying agents for water

mycotheologist - 27-4-2012 at 08:17

I know a drying agent for just about every common solvent but I don't know of any compounds that can be used to remove traces of other solvents from water. Right now I'm trying to obtain a pure water solution of potassium iodide/iodate so I can bubble Cl2 through it and oxidise the salts into I2 but the problem is that the last of the IPA seems to be impossible to boil off. If I add more water, is there some water insoluble compound I could add to absorb the alcohol?

Hexavalent - 27-4-2012 at 09:09

Just out of curiosity, why do you have isopropanol in your water?

There are better, easier and safer ways to make iodine from iodide salts BTW . . .the most common method is either adding sulfuric acid to the solution or hydrogen peroxide and hydrochloric acid, followed by filtration to remove the iodine precipitate.

The small amount of iodine that remains in solution with water can then either be kept in a seperate bottle as is, as a lab iodine/water solution, or have the elemental iodine removed from it by solvent extraction and evaporation of the solvent.

[Edited on 27-4-2012 by Hexavalent]

barley81 - 27-4-2012 at 11:57

I haven't seen this anywhere, but I believe that if you use HCl and H2O2, you could get ICl contamination with your I2. I used diluted sulfuric acid and H2O2 because of this. The user woelen suggested that you can melt the iodine precipitate (I would rinse it with water, decant the rinse, and chill, then add the sulfuric acid slowly to prevent overheating) under sulfuric acid to form a nice pellet, which can be sublimed easily in a clean beaker with a round-bottomed flask of ice on top. This is what I did, and I obtained an appealing crystalline product. I recommend this process, though I got only a 75% yield because I made the mistake of skipping the sulfuric acid addition and subliming it wet. This introduced lots of mechanical loss because I got little bits of iodine on the vial, crystallizing dish, filter paper, etc. It was my first experiment when I built my lab. You should be able to get a much better yield.


Since you have iodate/iodide, just add dilute sulfuric acid and hydrogen peroxide and then maybe try out what I wrote above. Others may correct me if my suggestion is bad.

[Edited on 27-4-2012 by barley81]

mycotheologist - 1-5-2012 at 06:34

Quote: Originally posted by Hexavalent  
Just out of curiosity, why do you have isopropanol in your water?

I had 500mL of iodine tincture which used IPA as the solvent instead of ethanol. I added KOH solution to oxidise the I2 into KI then boiled off the solvent. Now I'm left with damp KI that won't dry. Its slightly yellow so there is still some I2 dissolved in the IPA.

Quote: Originally posted by Hexavalent  

There are better, easier and safer ways to make iodine from iodide salts BTW . . .the most common method is either adding sulfuric acid to the solution or hydrogen peroxide and hydrochloric acid, followed by filtration to remove the iodine precipitate.

Yeah I know, I just want to try out the Cl2 bubbling method to learn.

EssOilChem - 1-5-2012 at 06:59

Quote: Originally posted by mycotheologist  

I had 500mL of iodine tincture which used IPA as the solvent instead of ethanol. I added KOH solution to oxidise the I2 into KI then boiled off the solvent. Now I'm left with damp KI that won't dry. Its slightly yellow so there is still some I2 dissolved in the IPA.


How damp? What does it look like? Still complete liquid?