If you read the posts on using HgI2 in MM Al/Hg Reduction, you would have realized that HgI2 is not as soluble as HgCl2, and HgI2 requires more time to amalgamate the aluminum. From what I have read, HgI2 will require at least 30 minutes to turn the foil into a dull and less shiny form of its original self, and this is the magic moment that MM speaks of.
If I were you, I would not use HgI2 from a tincture bottle simply because you don't know exactly how much Iodine is in the tincture. If you have some Iodine laying around, then make the HgI2 yourself; it's very easy. Just mix elemental Mercury with Iodine, and presto, you get a very fine dark red crystal; it looks beautiful.
So, how much HgI2 do you need for a typical 25g ketone MM Al/Hg reduction? Simple, just do the math....
Hg 200.59
Cl 35.453
I 126.9045
This is for Al/Hg using HgCl2...
2(35.45)CL + (200.59)Hg = 400mg
M = .001473350768 (the number of moles you need)
Don't forget that for each Mercury you have 2 Iodines, so you need 2 moles of Iodine for every 1 mole of Mercury.
[373mg (I) + 295mg (Hg)]
So, you need exactly 669mg of HgI2 for a 25g ketone MM Al/Hg
SWIM ran a test amalgamation by scaling the reaction down to 1/4. No ketone was used. This was conducted for observing the behavior and time required for the amalgamation using HgI2, instead of HgCl2.
6.9g Al
187ml Methanol
167mg HgI2
The HgI2 was first dissolved in the methanol, then the solution was added to the flask containing the foil boils previously grinded in the coffee grinder. The flask was stirred every 5 minutes.
After 15 minutes, small bubbles are observed rising from the bottom of the solution. The aluminum is still shiny.
After 30 minutes, the bubbles have increased slightly, and the aluminum is beginning to lose it shiny appearance. The solution is grey.
After 45 minutes, all the aluminum has lost its shiny appearance and the solution is beginning to thicken, but only slightly. The flask is getting very warm. It is at this point that the addition should be started. It's the magic moment.
So I think it is safe to conclude that you started you addition too early. On your next run, simply wait a bit longer and see how your yield is affected. If your yields go up, then you'll know for sure.