iodine for photosynthesis

[glenpaul]

Hi - its an age old question but I need to ask it again. What recipe do you use to make your iodine for the Starch in leaves prac? yr 11 Bio

[fibreweb]

I use 15gm Potassium Iodide plus 3 gm Iodine in 1 Litre of Distilled Water.
It takes a while to dissolve.
I have had few complaints in 10+ years

[rae]

I do the same as Fibre web.

[Graham Kemp]

It's called Lugol's Iodine Solution. (I2/KI).

For school practicals use: 15g KI, 3g I2, disolved to 1000L volume in H2O.

First disolve the potassium iodide in just a small amount of water (~20mL), then add the iodine to this. Only once the iodine is disolved, do you make up to final volume.

A small but concentrated KI solution will more quickly disolve the I2 than large but dilute one.

Crushing the iodine with a mortar and pestle may also help speed up the disolution process.

Store in brown glass, and in a cool and dark storage area.

[fibreweb]

Thanks Graham for that tip.
The length of time it has taken for Iodine to dissolve has frustrated me numerous times in the past
I have just added it to the relevant page in my "The Laboratory"