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    Home > Chemicals Industry > Chemical Technology > Industrial Ethylene Oxide (2)

    Industrial Ethylene Oxide (2)

    • Last Update: 2021-11-09
    • Source: Internet
    • Author: User
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    4 Test method

    4.
    1 Warning

    Some test procedures specified by the test method may lead to dangerous situations
    .
    The operator should take appropriate safety and health measures

    .

    4.
    2 General provisions

    Unless otherwise specified, only reagents confirmed to be analytically pure and grade 3 water specified in GB/T6682 are used in the analysis
    .

    The standard titration solutions, preparations and products used in the analysis are prepared in accordance with GB/T601 and GB/T603 unless other requirements are specified
    .

    4.
    3 Appearance

    Add a liquid laboratory sample to a 50mL colorimetric tube with a plug, and visually inspect it axially under a fluorescent lamp or sunlight
    .

    4.
    4
    Determination of
    ethylene oxide content

    4.
    4.
    1 Method summary

    100.
    00 subtracted by the sum of the ethylene oxide content of impurities, calculated
    ethylene oxide mass fraction
    .

    4.
    4.
    2 Result calculation

    The mass fraction w 1 of ethylene oxide content , the value is expressed in %, calculated according to formula (1):

    w 1 =100.
    00-∑wi……(1)

    Where:

    ∑wi— the sum of the mass fractions of various impurities (total aldehydes, water, acid, carbon dioxide ) in ethylene oxide, measured at 4.
    5, 4.
    6, 4.
    7 and 4.
    8 respectively

    .

    4.
    5 Determination of total aldehyde (calculated as acetaldehyde) content

    4.
    5.
    1 Principle of the method

    When the solution pH 3-4, sodium bisulfite is reacted with an aldehyde to generate α- hydroxy acid, titration solution titrated with standard iodine unreacted sodium bisulfite
    .
    Add sodium bicarbonate to change the pH of the solution to release the bisulfite that reacts with the aldehyde, and then titrate the released bisulfite with an iodine standard solution to calculate the total aldehyde content in the sample as
    acetaldehyde
    .

    4.
    5.
    2 Reagents

    4.
    5.
    2.
    1
    Sodium bicarbonate
    .

    4.
    5.
    2.
    2
    Anhydrous ethanol
    .

    4.
    5.
    2.
    3 Sulfuric acid solution: c(1/2H
    2 SO 4 )=0.
    5mol/L

    .

    4.
    5.
    2.
    4 Standard solution of sodium bisulfite: c(1/2NaHSO
    3 )= 0.
    10mol
    /L

    .

    Weigh 5g of sodium bisulfite , accurate to 0.
    1g, dissolve in a small amount of water, add 50mL of
    absolute ethanol and transfer to a 1000mL volumetric flask, add water to dilute to the mark
    .
    Adjust the pH value to 3.
    5
    with
    sulfuric acid solution (measured with a pH meter)
    .
    The pH value of this solution must be measured before each use.
    If the pH value of the solution is lower than 3.
    0, the solution cannot be used and should be reconstituted

    .

    4.
    5.
    2.
    5
    Standard solution of
    sodium bisulfite : c(1/2NaHSO 3 )=0.
    02mol/L

    .

    With sodium hydrogen sulfite solution was diluted (4.
    5.
    2.
    4) before use, and adjust the pH to 3.
    5

    .

    4.
    5.
    2.
    6 Iodine standard titration solution: c(1/2I
    2 )=0.
    1mol/L

    .

    4.
    5.
    2.
    7 Iodine standard titration solution: c(1/2I
    2 )=0.
    01mol/L

    .

    4.
    5.
    2.
    8 Starch indicator solution: 5g/L

    .

    4.
    5.
    3 Apparatus

    4.
    5.
    3.
    1 General laboratory equipment

    .

    4.
    5.
    3.
    2 Micro burette: 0.
    02mL sub-scale

    .

    4.
    5.
    3.
    3 Jacketed pipette: 5mL

    .

    A glass sleeve was installed outside the 5mL pipette, and both ends of the sleeve were plugged with rubber plugs
    .
    When in use, the jacket tube is filled with ice salt water

    .
    The schematic diagram of the jacketed pipette is shown in Figure 1

    .

    Figure 1 Schematic diagram of a jacketed pipette

    4.
    5.
    4 Analysis steps

    Use a pipette to draw 25.
    0 mL
    of sodium bisulfite standard solution, place it in a stoppered ground bottle containing 50 mL of water, cool to 0℃~4℃ in an ice bath, and take 5.
    0 mL with a jacketed pipette Place the laboratory sample in a ground-mouth flask, close the stopper, shake well, place in an ice bath for 30 minutes, add 1 mL of starch indicator solution, and titrate with an iodine standard titration solution until the solution is blue: keep it for 30 seconds without fading, no readings are counted

    .
    Add 1g of
    sodium bicarbonate and the blue color of the solution disappears
    .
    Titrate with the iodine standard titration solution through a micro burette until the solution appears blue and keep the color unchanged for 30 seconds as the end point.
    Read the volume of the consumed iodine standard titration solution

    .

    Note: When the aldehyde content of the sample is above 0.
    01% by mass, use
    sodium bisulfite standard solution (4.
    5.
    2.
    4) and iodine standard titration solution (4.
    5.
    2.
    6) for determination; the aldehyde content is 0.
    01% by mass fraction In the following, use
    sodium bisulfite standard solution (4.
    5.
    2.
    5) and iodine standard titration solution (4.
    5.
    2.
    7) for determination

    .

    At the same time of measurement, perform a blank test with the same amount of reagent solution without adding the sample according to the same procedure as the measurement
    .

     

     

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