Perhaps the most affordable way to obtain iodine is to extract it from a pharmacy alcohol solution of iodine.
Pharmacy iodine tincture is a water-alcoholic solution of iodine and potassium iodide.
To prepare a 5% solution of iodine take 50 weight parts of crystal iodine, 20 weight parts of potassium iodide, water and alcohol 95% equally to 1000 parts by volume.
Iodine is poorly soluble in water, so to increase the solubility of iodine potassium iodide is added to the tincture. Potassium iodide forms a complex with iodine:
KI + I2 <=> KI3
As follows from the recipe, 1 liter of tincture contains 50 g of iodine and 20 g of potassium iodide. To isolate iodine, we need to destroy potassium iodide. To do this, hydrogen peroxide and acid (sulfuric, in extreme cases - acetic acid) are added to the iodine tincture. Potassium iodide is oxidized. The necessary amount of substances is calculated using the equation:
2KI + H2O2 + H2SO4 = K2SO4 + I2 + 2H2O
(As you can see from the equation, acid is needed for the equilibrium to shift to the right).
As a result of oxidation of potassium iodide we, firstly, decrease solubility of iodine, and secondly, we obtain additional amount of iodine. Hydrogen peroxide and acid can be taken in some excess.
In order to further reduce the solubility of iodine, the tincture is diluted several times with water (this is done after adding peroxide and acid).
Now waitб until the iodine settles, decant (carefully drain off) most of the solution, and filter out the sediment of iodine. You will get wet iodine. For some experiments (e.g., obtaining iodide nitrogen) this will do, but for other experiments the iodine should be dried. This is not easy to do because iodine is volatile. If you leave wet iodine in the air, it will evaporate with the water.
Wet iodine is squeezed with a press. The iodine should then be dried in a desiccator over a dehydrating agent (e.g., anhydrous copper sulfate). Iodine should be stored in a zip bag, small jar, or other closed container.
In order to further purify iodine, it is possible to sublimate it. For this purpose, iodine is placed in a shallow beaker and covered with a round-bottom flask, in which cold water is poured. The beaker is placed on a sand bath, which is heated. Iodine sublimates from the bottom of the beaker and condenses on the cold surface of the flask.
Pharmacy iodine tincture is a water-alcoholic solution of iodine and potassium iodide.
To prepare a 5% solution of iodine take 50 weight parts of crystal iodine, 20 weight parts of potassium iodide, water and alcohol 95% equally to 1000 parts by volume.
Iodine is poorly soluble in water, so to increase the solubility of iodine potassium iodide is added to the tincture. Potassium iodide forms a complex with iodine:
KI + I2 <=> KI3
As follows from the recipe, 1 liter of tincture contains 50 g of iodine and 20 g of potassium iodide. To isolate iodine, we need to destroy potassium iodide. To do this, hydrogen peroxide and acid (sulfuric, in extreme cases - acetic acid) are added to the iodine tincture. Potassium iodide is oxidized. The necessary amount of substances is calculated using the equation:
2KI + H2O2 + H2SO4 = K2SO4 + I2 + 2H2O
(As you can see from the equation, acid is needed for the equilibrium to shift to the right).
As a result of oxidation of potassium iodide we, firstly, decrease solubility of iodine, and secondly, we obtain additional amount of iodine. Hydrogen peroxide and acid can be taken in some excess.
In order to further reduce the solubility of iodine, the tincture is diluted several times with water (this is done after adding peroxide and acid).
Now waitб until the iodine settles, decant (carefully drain off) most of the solution, and filter out the sediment of iodine. You will get wet iodine. For some experiments (e.g., obtaining iodide nitrogen) this will do, but for other experiments the iodine should be dried. This is not easy to do because iodine is volatile. If you leave wet iodine in the air, it will evaporate with the water.
Wet iodine is squeezed with a press. The iodine should then be dried in a desiccator over a dehydrating agent (e.g., anhydrous copper sulfate). Iodine should be stored in a zip bag, small jar, or other closed container.
In order to further purify iodine, it is possible to sublimate it. For this purpose, iodine is placed in a shallow beaker and covered with a round-bottom flask, in which cold water is poured. The beaker is placed on a sand bath, which is heated. Iodine sublimates from the bottom of the beaker and condenses on the cold surface of the flask.
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