In the labs, experimenters always take samples with fiberglass extraction thimbles. And weighing the extraction thimbles is quite important for the results of the experiments.
Does the cooling time have obvious influences when weighing the extraction thimbles that are taken out of the ovens? Actually, there is no concrete cooling time for the extraction thimbles defined in the technical criteria of monitoring. The specification only shows that the extraction thimbles should be weighed when they are cooled to room temperature in the desiccator. Experiments show that the cooling time is related to the number of extraction thimbles put in the dryer and the methods of placement. If we need to weigh the extraction thimbles in half an hour, we’d better not occupy more than 2/3 room of the dryer.
The other reason is the drying time. Sometimes the flue gas humidity of the environment is at a high level when sampling or working, which could cause the wet to weight of the extraction thimbles increases evidently after sampling. If we dry the extraction thimble at the temperature kept at 105~110℃ for an hour, there is still an error in the results because the dryness level of the extraction thimble is far less than before sampling. However, if we dry the extraction thimble for four hours at the same temperature, the situation of the extraction thimble can reach the standard requirements.