How to extract iodine 10 from kelp

1. Weigh 40g of dried kelp and roast it in an iron dish to make the kelp completely ashed.

2. Pour the kelp ash into a beaker, add 40ml, 20ml, and 10ml of distilled water to boil in turn. Combine the filtrate and the three extracts together, and the total volume should not exceed 30ml.

3. Add 2mol l of sulfuric acid solution to the filtrate to acidify until the pH value is neutral. (Kelp ash contains potassium carbonate, and acidification makes the layer neutral or weakly acidic, which is beneficial to the next step of oxidation and precipitation of iodine.) However, if the sulfuric acid is added too much, it is easy to oxidize the hydrogen iodide to produce iodine and lose).

4. Evaporate the acidified filtrate in the evaporation dish until dry and fry as much as possible, grind finely, and add 2g potassium dichromate solid to mix evenly.

5. Place the above mixture in a dry tall beaker and place a flask with water-cooled on the beaker mouth. Heat the beaker to sublimate the resulting iodine. Iodine vapor condenses at the bottom of the flask.

When no purple iodine vapor is generated, the heating is stopped. Remove the flask, scrape the solid iodine condensed from the flask into a small weighing flask and weigh it. Calculate the percentage iodine content in kelp.

Place the newly obtained iodine** in a brown reagent bottle.

Note: 5. The cooling rate should be controlled without condensate outside the distillation flask. ）

The temperature of iodine sublimation is more than 40 points.

It's time to know what to do.

Eat it in your stomach and digest it.

The operation process of iodine extraction from kelp is as follows:

1. First of all, the kelp should be chopped so that the extraction of iodine can be accelerated, and then the chopped kelp should be put into the soaking pool.

2. Because iodine is mainly in the form of inorganic iodide in kelp, it is easy to dissolve in water.

3. The soaking time and soaking times are determined according to the specific situation.

4. After soaking, filter out the soaking solution, and put the filtrate into the acidification and oxidation tank.

5. Add sulfuric acid and oxidant to turn iodide into free iodine.

6. Then through the operation process of resin adsorption and desorption, it can be made into high-purity iodine.

Mineral distribution of iodine:

Iodine exists in nature in the form of water soluble. It is scarce in nature, except for the high iodine content of kelp, marine fish, shellfish and other animals and plants in seawater (50-60 micrograms per liter of seawater), the content in most soils, rocks and water is very low.

Iodine is scarce in nature and ranks 47th in the earth's crust, and is very low in most soils, rocks and water, except for high levels in seawater (50 60 micrograms per liter of seawater).

Iodine in nature is mainly found in Chilean saltpeter mines in the form of sodium iodate naio3, and the iodine content in seawater is very small, but some organisms in the ocean (such as seaweed, kelp, etc.) have the ability to selectively absorb and enrich iodine, which is an important part of iodine**.

The above content referenceEncyclopedia - Iodine.

Ashing, soaking, filtration, chlorinating agent, distillation. 2i-+cl2=2cl-+i2。

The kelp is burned into ash, soaked and dissolved to obtain a suspension of kelp ash. Through filtration, an insoluble residue is obtained. The filtrate is a solution containing iodine ions.

An oxidant is added to oxidize iodine ions into iodine element, and iodine is extracted by organic solvent. The iodine element is then extracted by distillation. Equation:

The oxidant can be chlorine, which can oxidize iodide ions to iodine element, and the ionic equation of the reaction is: 2i-+cl2=2cl-+i2.

Experimental principle: The ash produced after burning dried kelp will contain iodine in kelp.

Exists in the form of iodine ions. Add deionized water.

And boil, so that the iodine ions are dissolved in water, the filtrate is filtered, and the pH of the filtrate is adjusted to be neutral. Evaporate the filtrate to give a white solid with potassium dichromate.

Mix well and grind. The mixture is heated in a tall beaker and the iodine element is sublimated, and the iodine is condensed at the bottom of the flask by capping the beaker with a round-bottomed flask filled with ice water. The resulting iodine is scraped off and weighed to calculate the yield.

Extraction of iodine from kelp.

Objective: To extract iodine from kelp.

Experimental principle]: The iodine ions are oxidized into iodine elements by oxidant, and then tested with starch.

2ki +Cl2== I2 +2kCl I2 encounters starch and turns blue.

Instruments required for the experiment]: balance, tweezers, scissors, iron stand, alcohol lamp.

Crucibles, crucible pliers, mud triangles, glass rods, separating funnels.

Selection of experimental drugs]: kelp, chlorine water.

Starch solution, carbon tetrachloride.

Experimental Procedures and Phenomena]:

Protocol x09 Phenomenon x09 Explanation and Reaction Equation.

On medium, add 20 ml of distilled water.

Bigger than in the water.

Discussion and exchange] 1. What is the function of burning? What other methods can be used to treat kelp other than burning?

2. In the fifth step, in order to oxidize i- to iodine element, can chlorinated water be added in excess dropwise? What other reagents can I use? How to test for iodine production?

3. How is iodine transformed during the whole experiment?

4.Is it possible to purify iodine by taking advantage of its sublimation properties? If so, how?

Experimental Extension] How to use a carbon tetrachloride solution from iodine.

Extraction of iodine elemental --- reverse extraction:

Add an appropriate amount of 40 NaOH solution drop by drop to the iodine-based carbon tetrachloride solution, and shake while adding until the carbon tetrachloride layer is no longer red. Iodine reacts to produce I- and I3 into the water.

The equation is 3i2+6oh- = 5i- + io3-+3h2o).

Divide the liquid, transfer the aqueous layer into a small beaker, and add 45% sulfuric acid dropwise to acidify, which can regenerate iodine element. Because the solubility of iodine element in water is very small, it can be precipitated.

The equation is 5i-+ io3-+ 6h+ =3 i2+3h2o).

Filtered to obtain elemental iodine crystals.

1. When separating and testing an element or component in a plant sample by chemical methods, can the sample be pretreated by burning at high temperature and then dissolving with water?

2. A research team determined oxalic acid in spinach.

and oxalate content (based on C2O42), the experimental procedure is as follows:

After pretreatment, spinach samples were soaked in hot water and filtered to obtain a solution containing oxalic acid and oxalate. ......

The following question: The method of "sample pretreatment" in step is . (A burns into ash, B grinds into juice).

Weigh 3g of dried kelp and brush the attachments on the surface of the dried kelp with a brush (do not wash with water). Chop the kelp, moisten it with alcohol (for easy burning) and place it in a crucible.

Burn the crucible with an alcohol lamp until the kelp is finished to ashes, stop heating and cool.

Transfer the kelp ash to a small beaker, then add 10ml of distilled water to the beaker, stir, boil for 2min 3min to dissolve the solubles and filter.

Add a few drops of sulfuric acid to the filtrate and add about 1 ml of H2O2 solution. Observe the phenomenon.

Take a small amount of the above filtrate and add a few drops of starch solution dropwise. Observe the phenomenon.

Add 1ml of starch solution to the remaining filtrate, shake and let stand. Observe the phenomenon.

Add NaOH solution to the starch-added solution, shake sufficiently, and pour the mixture into the designated container.