gdflp
Super Moderator
Posts: 1320
Registered: 14-2-2014
Location: NY, USA
Member Is Offline
Mood: Staring at code
|
|
Testing purity of Potassium Iodide
I recently obtained about 4oz of KI for a good price in a one time auction. The seller claimed the iodide was ACS reagent grade, but I highly doubt
this based on the price. Is there any way to test the KI for impurities(It doesn't have to be to ACS standards, but I'm looking for a quantitative
test so I can know it's around 98% or better purity.)
|
|
|
Galinstan
Hazard to Self
Posts: 53
Registered: 22-11-2013
Location: England
Member Is Offline
Mood: No Mood
|
|
take a small sample of your KI and convert it to iodine then dissolve it in an excess of a KI solution to form the triiodide ion and titrate against
sodium thiosulphate or other equivalent reducing agent to work out the percentage of your KI that is actually KI.
|
|
|
MrHomeScientist
International Hazard
Posts: 1806
Registered: 24-10-2010
Location: Flerovium
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Galinstan  | | take a small sample of your KI and convert it to iodine then dissolve it in an excess of a KI solution to form the triiodide ion and titrate against
sodium thiosulphate or other equivalent reducing agent to work out the percentage of your KI that is actually KI. |
This. I just did this recently myself, actually. Be aware that KI is somewhat reactive towards air, and solutions are slowly but easily oxidized to
iodine by oxygen. I found this out when leaving a clear KI + starch solution out over the weekend, and returned to find it brownish.
|
|
|
gdflp
Super Moderator
Posts: 1320
Registered: 14-2-2014
Location: NY, USA
Member Is Offline
Mood: Staring at code
|
|
Wouldn't that require known KI to do? I'd rather not drop $10 for an ounce of good KI, and have to wait a few weeks to get it and titrate the unsure
KI.
|
|
|
Zyklon-A
International Hazard
Posts: 1547
Registered: 26-11-2013
Member Is Offline
Mood: Fluorine radical
|
|
No. Re-read Galinstan's reply.
|
|
|
Paddywhacker
Hazard to Others
Posts: 478
Registered: 28-2-2009
Member Is Offline
Mood: No Mood
|
|
It would need some form of known standard unless you had laboratory standardised sodium thiosulfate solution. Potassium iodate is the usual
laboratory primary standard because it can be obtained very pure and it dries in the oven without decomposition and cools in the desiccator without
absorbing atmospheric moisture.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
