The automatic Kjeldahl nitrogen analyzer automatically completes water addition, acid addition, alkali addition, distillation, titration, automatic rinsing of the titration cup, emptying of digestive tubes, and calculation of results. No human intervention is required during the whole process. It is easy to operate, fast and accurate. Features. The protein in natural rubber (NR) has a great influence on its properties: the decomposition product of the protein has the effect of promoting NR vulcanization and enhancing the NR antioxidant properties; the protein has high water absorbance and conductivity, and the protein content is high in NR heat generation Large, poor dynamic performance, and easy to absorb moisture and mold, should not be used in the electronics industry. The nitrogen in NR is mainly present in the protein structure, and the general protein has a nitrogen content of 16%. The protein content of the NR can be indirectly known through the automatic Kjeldahl determination of nitrogen. Therefore, it is important to determine the nitrogen content of NR.
The NR digestion process with different amounts of sample and sulfuric acid is shown in Table 1. Since the digestive tube volume is 250 mL, the volume of the final solution cannot exceed 2/3, and the ratio of acid to alkali is 1:4, so the maximum amount of concentrated sulfuric acid is 20 mL. When the amount of sample is 2.0g, the amount of concentrated sulfuric acid is 10mL, 15mL, 20mL respectively, the digestion solution is dried, and the digestion is incomplete. When the amount of sample is 1.0g, the concentration of concentrated sulfuric acid is 20mL, the digestion time is the shortest, and the digestion is complete. When the amount of concentrated sulfuric acid is 10mL and 15mL, the digestion is incomplete, so the dosage of concentrated sulfuric acid is 20mL, and the amount of sample taken is 1.0g.
Automatic Kjeldahl nitrogen determination of NR nitrogen content of the optimum digestion process test conditions: sample 1.0g, concentrated sulfuric acid 20mL, catalyst 10g, 420 °C digestion 60min. Compared with the manual determination of NR nitrogen content, the automatic Kjeldahl tester method is simple and quick to operate, the test time is greatly shortened, and the human error is reduced. The precision of the instrument and the accuracy of the measured value are high.
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