Iodine/potasium iodide

loki · guinea pig

makes no difference putting salt in there... it might somewhat make the iodine less water soluble tho... but then you have to wash that salt residue back out afterwards anyway = more water = more I2 dissolution

gspot · Sat Jul 02, 2005 6:26 am

Ok, swim weighs out 60g KI and disolved into 150mls h2o. Then makes acidic with approx 20mls hcl 32%. To this he adds "4" 16oz bottles of h2o2. The solution turns dark purple and fizzes. It is stirred and left to sit for approx an hour. Now swim has a dark solution with no I2 crystals. Swim adds approx 500 mls h2o hoping to force i2 to precipitate but no luck. What was swims error? should sodium hypochlorite be added? More h2o?

Any feedback would be appreciated.

loki · guinea pig

yeah a lot more H2O for 60g, and more HCl (I'd guess about 60-100ml is required) and i think that is definitely be too much H2O2, by a long shot, you may find the solution will slowly turn pale over the next day or two, i made the same mistake while recovering some I2 recently. i initially thought it was too much water but when i saw it change, something i'd seen with over-oxidisation (for which reason I don't use hypochlorite) i knew what the culprit must have been.

gspot · Sat Jul 02, 2005 9:07 am

ok, swim added about 100-120mls more hcl and about 1000mls more h2o. Will wait about an hour or two and see if I2 has formed at the bottom. If not I will add more h2o.

Thanks for your help loki

loki · guinea pig

yeah you may have killed the iodine with peroxide tho, but you may still get precipitation. only a fairly small amount of peroxide is needed. there's info about the place on the proper amount of oxidising agent to use on the rhodium archives.

gspot · Sat Jul 02, 2005 4:17 pm

Ya, nothing precipitated. So i'll just throw this batch out and start again. I did find some info searching around that specified exact measurements to go by. This is what swim found:

1. Dissolve 100g KI in 300ml 10% HCl
or in 107ml 28% HCl
->300ml HCl 10% = 30g HCl
->30g HCl/280g/L = 0.107l of 28% HCl
->if using 28% hcl add 126ml h2o also
2. Add 100ml H202 (hydrogen peroxide 10%)(=10g H2O2)
or 333.33ml H2O2(3%)(10g/0.03g/ml=333.33ml)

2(KI) + H2O2 + 2(HCl) ------> 2(H2O) + 2(KCl) + I2

KI = 166g/mol
H2O2 = 34g/mol
2HCl = 36.4g/mol

SO -> 100g KCl = 0.602 mol
10g H2O2 = 0.301 mol
22g HCl = 0.602 mol
->Need pretty exact amounts of potassium iodide and hydrogen peroxide, but excess hydrochloric acid is OK. Thats why the recipe is for 30g equivalent of HCl when the balanced equation is for 22g HCl.
100% theoretical yield of I2 = 254g/mol x 0.301mol = 76.454g

As you add the H202, I2 falls out. This can
be filtered off, as it is only slightly soluble in water.
It is a good idea to wash it with some distilled water, as it might still contain some KCl.
When I do this in my dreams, I squeeze the filter to get the I2 crystals dry (not completely).
Then it can be purified by resublimation (see above).

reaction mechanism ( Smile

):

The H2O2 gives off oxygen ions.
These react with the hydrogen ions
from the HCl to form H20. The H202 is now H20, too, since the O left it, because they argued the whole time. Not a very stable relation, that H202.
Now that chlorine ions from the HCl are alone.
But they don't want to be alone. They want to be satified. So they grab the K ions from the KI, since they are stronger than those iodine ions.
Now the iodine ions are alone. And they want to be satisfied, too. So they react with temselves to form I2 Smile

.

D.G.(original) + Myles(modified)

Hope it works as stated.

gspot

loki · guinea pig

yeah when i do it i wrap the filtered crystals in a heap of dry filter papers and between two sides of a newspaper and between two phone books and stomp that bitch hard. presses a bloody lot of water out (after washing it with water). this is usually ok for a reaction, just ensure to reduce water volume by about 10% of the iodine weight (water being about 1kg/L, well 990g/L or something). I have done resublimation before too, it's pretty cool to watch, pink vapour, shiny black/purple/silvery crystals growing madly everywhere that's cool (they grow around the sides of the flask if it's not insulated, until the flask surface all gets hotter than 100 degrees). if only all halides were as friendly to work with as iodine Very Happy

gspot · Sat Jul 02, 2005 6:55 pm

It worked well! Swim was actually suprised at the amount of I2 that formed at the bottom. Used 100g KI, 96 mls hcl 32% + approx 200 mls dh20 and 333 mls h2o2 3%. All was done in a 1 Liter graduated flask. Although a lot of heat was generated with the addition of h2o2 so swim would recommend an ice water bath or some ice cubes in with the solution to help keep the iodine vapor to a minimum.

Swim doesn't know the yeild as of yet since it is still drying. Will probably use the paper towel method as loki sugested along with drying it in a desicator with calcium chloride.

gspot

loki · guinea pig

i have never seen significant vapour forming when doing it. maybe that reaction is calmed more by using more water, more water absorbs the heat. i've never worked with such a large amount of iodide before, the biggest i ever did was about 10g of KI, and i used 200ml of total solution when doing that.

loki · guinea pig

an excerpt of something i wrote a bit over a year ago that got a good rating on the hive:

bio · Working Bee

......swim has 37% HCl so that's 0.37g/ml which comes out to 0.3703ml.........

What am I missing here?

HCl 36.461g/m

37% 1.1837g/mL density

.4401g HCl/mL

Of course it is a little ridiculous to try and measure 1/10,000 of a gram with my 100mg resolution 2.61 Kg balance! Shocked

Sektor · Sat Aug 06, 2005 1:01 pm

this is wot swim done:

added:
75 ml of iodine tinct (25g/l)
75 ml of 30% peroxide
15 ml of 280/L Hcl
500 ml of H2O

mixed, then waited, then mixed some more,
gave it a day...
then filterd

did swim go wrong somewhere? got some grey shit but dunno if its any good...
could someone post if those measurements are wrong, cheers

Sektor · Sun Aug 07, 2005 2:18 pm

for fuck sakes, ok ok, so its a big balls up, so how can swim turn this black hash looking crap into I2 xtals? or is all hope lost.. cheers

MePrepuce · Sun Aug 07, 2005 8:28 pm