Iodine bromide (IBr) is measured for fat iodine values.

related topics .In this experiment, iodine value of fat was determined using iodine bromide (IBr), and the higher the iodine value, the higher the content of unsaturated fatty acids..Iodine bromide (IBr) fat iodine value determinationfat, unsaturated fatty acid chain has unsaturated bonds, can be added with halogen (Cl2, Br2, I2) reaction, the more unsaturated bonds, the more the amount of halogen added, usually expressed as "iodine value." Under certain conditions, the grams of iodine absorbed per 100g of fat are called the "iodine value" of the fat. The higher the iodine value, the higher the content of unsaturated fatty acids, which is an important constant for identifying and identifying fats.iodine bromide (IBr) was used in this experiment to determine iodine values. Part of IBr is added to unsaturated fatty acids, and the remainder is released with potassium iodide, which is titrated with sodium sulfate. The specific reaction process is as follows:plus reaction:-CH═CH-IBr-rarr; C2H2Ibr -release iodine: IBr-KI-rarr; KBrI2Titration: I2 plus 2Na2SO4 - srrr; 2NaI - Na2S4O6Reagents
and Equipment 1, Reagents Hanus Iodine Bromide Solution Take 12.2g iodine, put it in a 1500mL conical bottle, slowly add 1000mL ice acetic acid (99.5%), shake while
heating
in the water bath, so that iodine dissolves. After cooling, add about 3mL. Store in a brown bottle. 0.1mol/L standard sodium sulfate solution: 25g of crystalline sodium sulfate, dissolved in distilled water cooled after boiling (no CO2). Add Na2CO3 about 0.2g (sodium sulfate solution is most stable at pH9-10). After dilution to 1000mL, the standard 0.1mol/L potassium iodide solution was pressed to calibration: accurately measure 0.1mol/L potassium iodide solution 20mL, 10% potassium iodide solution 10mL and 1mol/L sulfuric acid 20mL, mixed evenly. Using 1% starch solution as an indicator, the sodium sulfate solution was derated, and the concentration of sodium sulfate solution was calculated according to the reaction type listed below, and diluted to 0.1mol/L with water..KIO3 , 5KI , 3H2SO4 , 3K2SO4 , 3I2 , 3H2O I2 , 2Na2S2O3 , 2NaI , Na2S4O6pure carbon tetrachloride; 1% starch solution (dissolved in saturated sodium chloride solution);, the materialpeanut oil or lard.III, equipmentiodine bottle (or conical bottle with glass plug), brown, colorless
titration tube
each 1, suction tube,
tube
,
balance
. 4, operating method accurately named 0.3-0.4g peanut oil 2 servings, placed in two
dying
iodine bottles, do not stick oil to the bottleneck or wall. Add 10mL of carbon tetrachloride and shake gently to dissolve all the oil. Carefully add 25mL of iodine bromide solution (Hanus solution) with a titration tube so that the solution does not come into contact with bottlenecks. Cover the plug and add a drop of 10% potassium iodide solution between the glass plug and the mouth of the bottle to close the gap to avoid the loss of iodine volatilization. Place 30min in the dark at 20-30C and shake gently from time to time. Immediately after placing 30min, carefully open the glass plug so that potassium iodide solution next to the plug flows into the bottle and is not lost. Rinse the liquid from the glass race and the bottleneck into the bottle with the newly made 10% potassium iodide 10mL and distilled water 50mL. Quickly titrate to light yellow with a solution of 0.1mol/L sodium sulfate. Add 1% starch solution about 1mL and continue titration. Near the end of the time, the force oscillation, so that iodine from the carbon tetrachloride layer into the aqueous solution. Then titring until the blue disappears, i.e. reaching the end of the titring. Another 2 blank control, except without samples, the rest of the operation is the same. After titration, pour the waste liquid into the waste tank in order to recover carbon tetrachloride. Calculating iodine values Pressed to calculate iodine values: iodine values s (A-B) ×T×100/C , A - average milliliters of Na2S2O3 solution used for titration blanks, B - Average number of milliliters of Na2S2O3 solution used in the sample after titration iodization, C - weight of the sample (g), T - 1mL 0.1mol/L sodium sulfate solution equivalent to the grams of iodine: 5, Note (1) iodine bottle must be washed, dry, otherwise the oil in the bottle contains water, causing incomplete reaction. After adding iodine reagents, if the color in the iodine bottle is found to be light brown, indicating that the reagents are not enough, another 10-15mL reagents must be added. (2) If iodine reagents are added, the liquid becomes cloudy, indicating that the grease dissolves incompletely in CCl4, and some CCl4 can be added. (3) near the end of the titration, force oscillation is one of the keys to the success or failure of this titration, otherwise it is easy to drop too much or insufficient. If the oscillation is not enough, the CCl4 layer will appear purple or red. At this point, the iodine should be oscillated so that iodine enters the water layer. (4) starch solution should not be added too early. Otherwise, the titration value is high.
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