This standard specifies the method for determining a small amount of manganese in natural rubber latex. This method is applicable to natural latex from Hevea brasiliensis, and is not applicable to compound latex or vulcanized latex. GB 8296-1987 Determination of manganese content in natural rubber latex (potassium periodate photometric method) GB8296-1987 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of manganese content in natural rubber latex
(Potassium periodate photometric method)
Natural rubber latex--- Determination of manganese content--- Potassium periodate photometric method Scope of application
UDC 678. 031
GB8296-87wwW.bzxz.Net
This standard adopts the international standard ISO1655-1975 "Raw rubber and latex-Determination of manganese content--Potassium periodate photometric method". This standard specifies the method for determining a small amount of manganese in natural latex. This method is applicable to natural latex from Hevea brasiliensis, not to compound latex and vulcanized latex.
2 Reference standards
GB8290-87 "Sampling of natural concentrated latex". GB8298-87 "Determination of total commercial content of natural concentrated latex". 3 Sampling
Sampling shall be carried out in accordance with the method specified in GB8290. 4 Summary of the method
Ashe the rubber and potassium hydrogen sulfate together to convert the manganese in it into soluble substances. After the ash is dissolved in dilute sulfuric acid, any iron ions present in the solution are complexed with phosphoric acid and boiled and oxidized with potassium periodate to permanganate, and then colorimetric determination is carried out. 5 Instruments
Ordinary laboratory analytical instruments and
5.172-1 type spectrophotometer, with a colorimetric cell with an optical path length of 10 to 50 mm. 5.2 Crucible, quartz crucible or porcelain crucible with a nominal capacity of 50 to 80 mL. 5.3 High temperature furnace, capable of maintaining 550 to 600 ± 20°C, 6·Reagents
The purity is above analytical grade, and the water quality requirement is twice distilled water. 6.1
Potassium hydrogen sulfate;
6.2 Potassium periodate;
Sulfuric acid (sulfuric acid content 95~98%);
Dilute sulfuric acid 117 Sulfuric acid solution;
6.5 Phosphoric acid (phosphoric acid content 85~90%);
Dilute phosphoric acid 111 Phosphoric acid solution
Approved by the Ministry of Agriculture, Animal Husbandry and Fisheries of the People's Republic of China on July 10, 1987 and implemented on June 1, 1988
6.7 Manganese standard solution
GB 8296—87
Weigh 0.770g manganese sulfate (MhSO·H,O) and place it in a small beaker. Dissolve it in water containing 2mL sulfuric acid. Transfer the solution to a 500mL volumetric flask and dilute to the mark. This solution can be stable for at least one month. Use a pipette to draw 20mL of the above stock solution into another 500mL volumetric flask and dilute to the mark. This solution contains 20ug manganese per milliliter and should be freshly prepared with the stock solution when used. 7 Preparation of standard working curve
Use a microburette to take 0, 0.25, 0.50, 0.75, 1.00, 1.25, and 1.50mL of manganese standard solution (1mL=20ug manganese) and place them in 7 150mL tall beakers respectively. Add 20mL of dilute sulfuric acid (6.4), 3mL of dilute phosphoric acid (6.6), 5g of potassium hydrogen sulfate, and 0.3g of potassium periodate to each beaker. Heat to boiling for 20 minutes, while continuously adding distilled water to keep the solution volume at 30-40 mL. After the solution cools to room temperature, transfer it to a 50 mL volumetric flask and dilute it to the mark with double distilled water. In a 72~1 type spectrophotometer, use a wavelength of 525 nm and a 50 mm colorimetric cell to measure the light transmittance of the solution, convert it into optical density, subtract the blank optical density, use the optical density as the ordinate and the milliliters of the manganese standard solution as the abscissa, and draw a dotted line to form the standard working curve. 8 Operation steps
Weigh 10g of dried total solid latex, cut it into strips (1-2mm in diameter), place it in a silica gel dryer for 24h, weigh it to 1mg, wrap it with quantitative filter paper with a diameter of 150mm, place it in a 50-80mL quartz crucible or porcelain crucible, add 5g of potassium hydrogen sulfate on the surface, cover it and place it in a high-temperature furnace to heat it up. Initially control it at 220-250℃. If it starts to smoke, stop heating it up. Then increase the temperature by 20℃ every half hour. When it reaches 450℃, start increasing the temperature by 50℃ every half hour until it reaches 550-600℃, stop heating it up, and keep it for 4-8h until it turns into white with no black spots. Turn off the high-temperature furnace, wait until it cools down to below 200℃, take out the crucible and let it cool down slightly. In each, add 20mL of dilute sulfuric acid (6.4), place the crucible on a steam bath and heat for 30 minutes, wash the crucible contents into a 150mL tall beaker, and remove the insoluble solids with a glass rod. Boil the solution slightly for 10 minutes, take it out and cool it slightly, filter the solution through a glass filter funnel (specification 100×2) into a 150mL tall beaker, rinse the funnel and insoluble matter with about 20mL of water, add 3mL of dilute phosphoric acid (6.6) to the filtrate to completely remove the yellow interference of iron ions. If necessary, add 1mL of dilute phosphoric acid. Add 0.3g of potassium periodate to the solution, heat to boiling and keep for 20 minutes, and continuously add double distilled water to maintain the volume of 30-40mL. Take out the tall beaker and let it cool to room temperature. Transfer the solution into a 50mL volumetric flask and dilute to the scale with twice distilled water (the color should be stable for several hours after mixing). At the same time, make a blank test. The prepared solution was measured colorimetrically in a 72-1 spectrophotometer at a wavelength of 525nm and a 50mm colorimetric cell. The transmittance was recorded and converted into optical density. The blank optical density was subtracted and the corresponding milliliters of manganese standard solution V was found by comparing with the standard working curve. 9 Calculation of manganese content
Manganese content, mg/kg total solids = ×r
Where: V corresponds to milliliters of manganese standard solution, mL; manganese content of manganese standard solution, ug/mL;
n--total solid mass of the sample, 8.
Additional remarks:
This standard is under the jurisdiction of the Agricultural Reclamation Bureau of the Ministry of Agriculture, Animal Husbandry and Fisheries. This standard was drafted by the South China Tropical Crop Product Processing and Design Institute. The main drafter of this standard was Zhou Hongqing.
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