Moisture determination procedure of high-low constant temperature drying method

Constant weight of the aluminum box [dry the clean aluminum box, bake at 130 ℃ for 1 hour, take it out, cool it and weigh it, then continue to bake it for 30 minutes, cool it and weigh it, until the error of the two drying results is less than or equal to 0.002g, take the average of the two weights value.

Pre-adjust the oven temperature [low temperature drying method 103±2°C, high temperature drying method 130-133°C.

Sample preparation [When sampling, first mix the samples in the airtight container (do not directly touch the seeds with your hands), take out two independent test samples of 15-25g, and put them into ground-mouth bottles. . The samples to be grinded shall be processed according to the requirements in Table 11-1 and immediately put into the grinding bottle for later use. It is better to weigh the samples immediately to reduce the change of sample moisture. (Remember: two samples should be taken, ground separately, and an independent replicate sample should be taken from each ground sample, not two replicates from one ground sample.) Remaining sent samples It should continue to be stored in an airtight container for re-examination.

Weighing and drying [Mix the treated samples fully in a grinding bottle, weigh two samples of 4.500-5.000g with a balance with a sensitivity of 0.001g, put them into aluminum boxes with constant weight, and record the box number , the weight of the box and the actual weight of the sample. When the sample is flattened, the lid of the box should be opened, placed at the base of the aluminum box, and put into the oven. The distance between the aluminum box and the mercury bulb of the thermometer is 2-2.5cm. When the temperature in the box rises to the specified temperature, start timing (remember: the timing should start when the oven temperature rises to the working temperature), after drying for 1 hour or 8 hours, put on yarn gloves, open the box door, quickly close the lid, and take out Aluminum box, placed in a desiccator to cool to room temperature (about 30-45 minutes) and then weighed.

Calculation and reporting of results [Calculate the moisture percentage of the seeds based on the weight lost after drying, the allowable difference between the two measurement results shall not exceed 0.2%, if it exceeds, it needs to be re-measured, and the final result shall be filled with one decimal place. ]