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    Home > Chemicals Industry > Chemical Technology > Determination of total ash in flour (1)

    Determination of total ash in flour (1)

    • Last Update: 2021-07-25
    • Source: Internet
    • Author: User
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    Ash content is one of the main indicators for the classification and grading of flour in China, and is the main reference basis for the inherent quality and use performance of flour
    .


    This training uses the direct ashing method (according to "GB5009.


    1.
    Purpose requirements

    (1) Familiar with basic operation skills such as the use of high-temperature electric furnace and crucible processing, sample carbonization, ashing, and balance weighing
    .

    (2) Learn and understand the principle and operating points of the direct ashing method to determine ash content
    .

    (3) Master the measurement method and operation skills of ash in flour
    .

    2.
    Principles of training

    A certain amount of samples are carbonized and burned in a high-temperature furnace, so that organic substances are oxidized and decomposed, and escape in the form of carbon dioxide , nitrogen oxides and water, while inorganic substances are sulfates , phosphates , and carbonates.
    Inorganic salts, chlorides, and other inorganic salts and metal oxides remain in the form of ash.
    These residues are ash.
    Weigh the weight of the residues to calculate the total ash content in the sample
    .

    3.
    Training supplies

    (1) Muffle furnace: temperature ≥600℃
    .

    (2) Analytical balance: Sensitivity is 0.
    1mg
    .

    (3) Porcelain crucible: 60mL
    .

    (4) Dryer: There is desiccant inside
    .

    (5) Electric heating plate or electric stove
    .

    (6) Water bath
    .

    (7) Crucible tongs (large and small)
    .

    (8) Hydrochloric acid solution: 1:4
    .

    (9) A mixture of 0.
    5% ferric chloride solution and equal amount of blue ink
    .

    4.
    Safety reminder

    When the muffle furnace is working, it is strictly forbidden to put flammable and explosive materials around it; when taking and placing items into the muffle furnace, you must wear protective gloves and use corresponding tools (such as long-handled crucible tongs) to avoid burns or burns ; When opening the door of the muffle furnace to cool down, people should stay away from the muffle furnace to avoid scalds caused by radiation; do not plug and unplug the electrical plug with a wet hand to avoid the risk of electric shock
    .

    5.
    Operation steps

    (1) Preparation of the porcelain crucible: Boil the crucible with hydrochloric acid (1:4) for 1 to 2 hours, wash and dry; the crucible used should be marked (with 0.
    5% ferric chloride solution and the same amount of blue ink) The mixed solution is written on the outer wall and lid of the crucible with a number); placed in a high temperature furnace at (550±25)℃ for 0.
    5h; moved to the furnace mouth and cooled to about 200℃, then moved into a desiccator, and cooled to After room temperature, accurately weigh; then put it into a high-temperature furnace and burn for 30 minutes, take it out and cool and weigh it until it has a constant weight (the difference between the two weighings does not exceed 5 mg)
    .

    (2) Weigh the sample directly weigh 5-8g of flour into the crucible (accurate to 0.
    0001g) or use the sample after measuring the moisture (do not ignore the previous moisture when calculating the result)
    .

    (3) Measurement: Place the crucible on an electric hot plate or electric furnace and heat it carefully to make the sample fully carbonized to smokeless
    .


    Then put it in a muffle furnace and burn at (550±25)℃ for 4h


     

     

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