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鸡蛋壳(Egg shell)

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鸡蛋壳(Egg shell)鸡蛋壳(Egg shell) 鸡蛋壳(Egg shell) Four. Experimental principle and experimental procedures The main component of egg shell is CaCO3, followed by MgCO3, protein, pigment and a small amount of Fe, Al. 1. pretreatment: first the eggshell and eggshell, boil for 5 ...

鸡蛋壳(Egg shell)
鸡蛋壳(Egg shell) 鸡蛋壳(Egg shell) Four. Experimental principle and experimental procedures The main component of egg shell is CaCO3, followed by MgCO3, protein, pigment and a small amount of Fe, Al. 1. pretreatment: first the eggshell and eggshell, boil for 5 ~ 10min, the removal of protein film inside the eggshell surface, and then placed in a beaker with eggshell drying oven at 105 DEG C, grinded into powder storage weighing bottle, put the spare dryer. 2. to determine the weighing eggshell quantity: test scheme with constant weighing range (eggshell to determine the concentration of standard solution, about 25~30ml, according to the calculation of the amount of eggshell, while also taking into account the weighing error (called > 0.12g). If the amount is too small or the sample can be called large (considering uniform with 250ml shell solution, 25ml shift experiment). Case 0.01 mol * L-1EDTA x 25ml x 10-3 x 100 = 0.025g. Weigh accurately 0.25g shell, equipped with a 250ml solution, and then shift the 25ml experiment). 3. determination of calcium and magnesium content in eggshell (design experiment) The determination of the eggshell Ca EDTA titration method, total Mg In pH=10, with chrome black T as indicator (or K-B indicator), EDTA is a direct measure of Ca2+, total Mg2+, in order to improve the coordination selectivity in pH=10, adding masking agent triethanolamine and make the Fe3+, Al3+ plasma generated more stable complexes, to exclude them on Ca2+, Mg2+ ion interference measurement. Does not affect the pigment. Determination of Ca, Mg total quantity: accurately determine a certain amount of eggshell powder (accurate 0.25g eggshell, 250ml accurate solution, and then move 25ml experiment) in the beaker, cover the surface dish, Carefully add 6 mol L-1 HCl 4 ~ 5mL, dissolved from the cup mouth, add 50ml of water, low heat removal (CO2 = CaCO3, the decrease in anti low acidity. A small amount of protein film insoluble), cooling, quantitative transfer to 250mL capacity bottle, dilute to close to the calibration line, if there is foam, drop 2 ~ 3 drops of 95% ethanol (defoaming agent), after the foam is eliminated, drop water to the scale line shake. Accurate draw test solution 25.00mL, a 250mL conical flask, add 1 drops of methyl red solution, using 5mol/L NH3 H2O and to the red, yellow, and deionized water 20mL, triethanolamine 3mL, Mg-EDTA 5ml. Add NH4Cl-NH3 / H2O buffer 10mL, shake it well. Drop 3 drops of chromium black T indicator, with EDTA standard solution (under the same conditions calibration, reference substance CaCO3) titration to the solution, from purple to pure blue, that is reached the end point, parallel three copies. The total amount of Ca2+ and Mg2+ was calculated according to the volume of EDTA consumed, represented by the content of CaO. The determination of Ca in the eggshell of acid-base titration, total Mg The carbonate in eggshell can react with HCl, and the excess acid can be dripped back by standard NaOH. The total amount of Ca and Mg in eggshell is determined according to the standard hydrochloric acid volume of reaction with carbonate, and the result is expressed by CaO mass fraction. 1) 0.1mol L-1 NaOH preparation: 2gNaOH solid in small beaker, dissolved in H2O, then moved to plastic reagent bottle, diluted with distilled water to 500mL, with rubber stopper, shake well. 2) 0.1mol L-1 HCl preparation: the amount of concentrated hydrochloric acid 4mL in 500mL reagent bottle, diluted with distilled water to 500mL, stamped, shake. 3) pH calibration: weigh accurately reference material Na2CO3 (180 DEG 2H dryer drying, cooling) in 3 0.17g Erlenmeyer flask, deionized water, add 30mL to CO2 and the boiling cooling shake, dissolving, adding 1 ~ 2 drops of methyl orange indicator, using the above prepared HCl solution to orange end point. Calculate the exact concentration of HCl solution. Then the HCl standard solution was used to calibrate the concentration of NaOH solution (or to calibrate NaOH with KHC8H4O4). 4) Ca, total amount of Mg: accurate pretreatment of eggshell powder 0.12~0.13g (accurate to 0.1mg). Pay attention to the eggshell, the better it is, the more insoluble it is About three parts (or 1.2g, 250ml accurate solution, and then 25ml experiment). Due to eggshell insoluble, but also consider: with 1 mol / L-1 Hcl, accurate dilution of 10 times, calibration, respectively calculate 0.1 mol ? L-1 and 1 mol / L-1Hcl concentration. 1.2g 40.00ml 1 mol L-1 shell with Hcl dissolved, completely dissolved after sizing, without heating), were placed in 3 Erlenmeyer flask with acid burette by Hcl standard solution is added to the calibrated 40mL drops 0.1 mol around L-1 (to be precise readings), water bath heating (< 50 (c) dissolved normally not be heated, HCL decrease, but the 1H is still not dissolved, eggshell float on the liquid), cooling, adding methyl orange (CO2) indicator 1 ~ 2 drops, with NaOH standard solution dropping back to orange. Record and calculation. Matters needing attention: 1. because the acid is thinner, it needs to be heated for a certain time when dissolving. There are insoluble substances in the sample, such as protein and so on But it has little effect on the determination. 2. PH 4.4, Fe, Al interference, does not affect the pigment. The determination of Ca, Mg content in eggshell by Potassium Permanganate The use of Ca2+, Mg2+ and oxalate in eggshell formation of insoluble calcium oxalate precipitation (Ksp=4 * 10-9) and magnesium oxalate precipitation (Ksp=4.83 * 10-6), the filtering and washing the precipitate dissolved after separation, determination of oxalate content by Potassium Permanganate method, calculate the content of Ca, CaO. Reaction is as follows: Ca2+ + C2O42- = CaC2O4: CaC2O4 + 2H+ = Ca2+ + H2C2O4 5H2C2O4 + 2MnO4- + 6H+ + 10CO2 = ==2Mn2+ + 8H2O Some metal ions (Ba2+, Sr2+, Pb2+, Cd2+, etc.) can precipitate with C2O42- and interfere with the determination of Ca2+ and Mg2+. Weigh accurately eggshell powder three, 0.12~0.13g each, were placed in a 250mL beaker with 1:1 HCl 2.5ml and H2O 20mL, dissolving, heating, up to CO2 (anti CaCO3 case), if there is no dissolved protein, can filter. The filtrate placed in a beaker, then add 5% ammonium oxalate solution (50ml Ca, Mg precipitation excess, completely, if the precipitation (may) CaC2O4, CaCO3), adding HCl to dissolved concentration (Ca2+), and then heated to 70 to 80 DEG C (solubility, high temperature decomposition, adding oxalic acid) 2 ~ 3 drops of methyl orange solution was added dropwise red, 10% ammonia (slow, slow increase of pH, the concentration of C2O42- increased slowly, stirring constantly, until the precipitation) and yellow (PH=4.4, CaC2O4 and solubility minimum) ammonia escape far. The solution is placed over aging (or heating in a water bath (less than or equal to 85 DEG C) 30min Chen Hua), the ordinary standard funnel method pouring filtration, precipitation after washing, until no Cl- ion (KMnO4 oxidation of Cl- ions). Then, the vertical precipitation with the filter paper posted on the previously used wall on the sedimentation beaker, with 1 mol/L sulfuric acid precipitation by 50mL filter washed into the beaker, then wash the bottle blowing 1 ~ 2 times, this filter paper, on clean surface. Then, a dilute solution to volume is about 100mL, is heated to 70 to 80 DEG C, while KMnO4 standard solution (Na2C2O4 thermal calibration benchmark (note) titration titration beaker operation) until the solution is pale red, then put into the solution in the filter (filter paper consumption KMnO4 standard solution, the input end point near break) and fade, adding to the light red does not disappear in 30s so far. Calculate the mass fraction represented by CaO.
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