Large amount of gas will be created during the digestion period, so the weight of the sample should be restricted within the range of 0.1-0.2 g, and the detailed weight is determined by the organic content of the sample. Like the petroleum, it's belonging to the class of heavy organic substance, and the safe limitation weight of the sample is no more than 0.2 g. For the un-familiar sample weight of 0.1 g and increase the sample weight step by step later on. Or the sample can be pre-treated in an opening container.