Preparation of iodine test, preparation method of iodine solution

The configuration method of <> iodine solution is as follows:

1. Weigh iodine grams with a tray balance and put it into a glass milk bowl containing 100 ml of 36% KI solution.

2. Grind to completely dissolve, then transfer to a beaker.

3. Add 3 drops of hydrochloric acid and an appropriate amount of distilled water to make the solution in the glass milk bowl 1000 ml to obtain iodine solution.

The iodine standard solution is prepared and calibrated as follows:

1. Preparation: iodine standard solution c =

Weigh 13g of iodine and 35g of potassium iodide.

Dissolve in a small amount of water, then transfer into a 1L brown reagent bottle, dilute to 1L with water, and shake well.

2. Calibration: 1. Principle:

2Na2S2O3+I 2NAI+NazS4O2, calibration: accurately measure 20ml of 25ml iodine solution, add 50ml of water and hydrochloric acid, shake well, add starch indicator when titrating near the end point (yellowish) with NAS0 standard solution, and continue titration until the blue color of the solution disappears as the end point.

Calculation: c=v1*c1 v

Where: V1-titration consumes NazS2O3 standard solution body filial piety sock volume, ml.

C1-NazS2O3 standard solution concentration.

mol/l。

v- Aspirate iodine volume, ml.

Synthesis method. Potassium iodide belongs to iodine preparations, and its preparations are potassium iodide tablets. The synthesis process of potassium iodide is:

Iodine is dissolved in potassium hydroxide solution to generate a mixture of potassium iodide and potassium iodate, evaporated to dry, and then mixed with carbon powder to heat to reduce potassium iodate, that is, to obtain potassium iodide, the relevant reaction formula is:

3i2+6koh=5ki+kio3+3h2okio3 +3c=ki+3co

Methods for the production of potassium iodide.

At present, most of the domestic formic acid reduction method is used to produce potassium iodide. That is, potassium iodide and potassium iodate are produced by the reaction of iodine and potassium hydroxide, and then potassium iodate is reduced with formic acid or charcoal. However, iodate is generated in this method, and the product should not be used as a food additive.

Food-grade potassium iodide can be produced by the iron filings method.

The iron filings method uses iodine and iron filings as raw materials. One part of iron filings was placed in the reactor, 7 parts (mass) of water were added, and the iodine was added in batches at 65 ct (iodine is easy to sublimate if the temperature was too high). After adding iodine tablets, the solution is dark reddish-brown, and the second batch of iodine tablets can be added only after the solution is light green.

The iron filings are then filtered out to obtain an ferrous iodide solution, which is added to a 10:3 (mass) aqueous potassium carbonate solution to generate an iron carbonate precipitate and a potassium iodide solution. The solution is left standing, the supernatant is precipitated after clarification, heated and concentrated to relative density, and then filtered; When the filtrate continues to evaporate to relative density, filter while hot.

Cooled to 60 70 to stand for crystallization, separated and dried at 70 90 to obtain anhydrous potassium iodide products.

fe+i2fei2

fe i2+k2co3—2ki+feco3

The iodine standard solution is prepared and calibrated as follows:

1. Preparation: iodine standard solution c =

Weigh 13g of iodine and 35g of potassium iodide, dissolve them in a small amount of water, then move them into a 1L brown reagent bottle, dilute them to 1L with water, and shake well.

Second, the standard filial piety socks are fixed:

1. Principle: 2Na2S2O3+I 2NAI+NazS4O2, calibration: accurately measure 20ml of 25ml iodine solution, add 50ml of water and hydrochloric acid, shake well, add starch indicator when titrating near the end point (yellowish) with NAS0 standard solution, and continue to titrate until the blue color of the solution disappears as the end point.

Calculation: c=v1*c1 v

Where: V1-titration consumes NazS2O3 standard solution volume, ml.

C1-NazS2O3 standard solution concentration, mol l.

v- Aspirate iodine volume, ml.