# Analysis of the Organic Chemical Fractions of Three Coal Extracts
## 2 Materials and Methods
### Graded Extraction of Coal  
Weigh 10 g of each pre-prepared coal sample, build the Soxhlet extraction device, place the coal samples in a filter paper tube in the Soxhlet extractor, add the first level of extraction solvent CS\({}_{2}\) 150 mL extraction, an extraction temperature slightly lower than the boiling point of the solvent, an extraction time of 60 h, and every 12 h, replace the fresh solvent to prevent saturation of the solvent extraction. Collect the extracts after each level of extraction is completed, and repeat the extraction of the last level of solvent according to the above steps until all 7 levels of solvent extraction are completed. A total of 21 groups of extracts were obtained from three kinds of coal samples, which were PS-CS\({}_{2}\), PS-HEX, PS-BEN, PS-MET, PS-ACE, PS-THF, PS-THF/MET, DT-CS\({}_{2}\), DT-HEX, DT-BEN, DT-MET, DT-ACE, DT-THF, DT-THF/MET, GT-CS\({}_{2}\), GT-HEX, GT-BEN, GT-MET, GT-ACE, GT-THE, and GT-THF/MET. PS-CS\({}_{2}\): Pingshuo Coal CS\({}_{2}\) Extract; PS-HEX Pingshuo Coal Hexane Extract; PS-BEN: Pingshuo Coal Benzene Extract; PS-MET: Pingshuo Coal Methanol Extract; PS-ACE: Pingshuo Coal Acetone Extract; PS-THF: Pingshuo Coal THF Extract; PS-THF/MET: Pingshuo Coal THF mixed with Methanol Extract. DT-CS\({}_{2}\): Datong CS\({}_{2}\) Extract; DT-HEX: Datong Hexane Extract; DT-BEN: Datong Benzene Extract; DT-MET: Datong Methanol Extract; DT-ACE: Datong Acetone Extract; DT-THF: Datong THF Extract; DT-THF/MET: Datong THF and Methanol Mixed Extract. GT-CS\({}_{2}\): Geiting CS\({}_{2}\) Extract; GT- HEX: Getting Hexane Extract; GT-BEN: Getting Benzene Extract; GT-MET: Geeting Methanol Extract; GT-ACE: Geiting Acetone Extract; GT-THF: Getting THF Extract; GT-THF/MET: Getting THF/Methanol mixed Extract. The extraction rate for each solvent was calculated according to the following equation:  
\[\eta=\frac{100\times W_{1}}{(100-A_{ad}-M_{ad})*W/100} \tag{1}\]  
where the \(\eta\) is the extraction rate of solvent, %; \(W_{1}\) is the mass of extract, g; \(W\) is the mass of coal sample to be extracted, g; \(A_{ad}\) is the ash of coal, %; \(M_{ad}\) is the moisture content of coal, %. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Equipment Name** & **Equipment Model** & **Address** & **Manufacturer** \\ \hline Elemental Analyser & Elementar Vario ELII & Hebi, China & Hebi Yingtai Electronic and Electrical \\ sulfur meter & 5E-S3200 & Yuncheng, China & Anglance Co., Ltd. \\ Gas Chromatography/Mass & 7890A-5975C & Santa Clara, CA, USA & Agilent Corporation of the \\ Spectrometry (GC-MS) & 7890A-5975C & Santa Clara, CA, USA & United States \\ \hline \hline \end{tabular}  
* The instruments shown in the table are all freely available in the laboratory or school, and all of them are useful in the course of the experiment. The reagents and specifications used in the experiment are listed below in Table 2.  
\end{table} 
Table 1: _Cont._ \begin{table}
\begin{tabular}{c c c} \hline \hline
**Reagent Name** & **Standard** & **Address** & **Manufacturer** \\ \hline CS\({}_{2}\) & & Tianjin Kemio Chemical Reagent Co., Ltd. \\ N-hexane & & Tianjin Damao Chemical Reagent Factory \\ Benzene & & Tianjin Fuyu Fine Chemical Co., Ltd. \\ Methanol & & Tianjin Fuyu Fine Chemical Co., Ltd. \\ Acetone & & Tianjin Fuyu Fine Chemical Co., Ltd. \\ THF & & Tianjin Fuyu Fine Chemical Co., Ltd. \\ \hline \hline \end{tabular}  
* The reagents shown in the table were purchased through regular channels. These reagents are analytically pure for experimental purposes.  
\end{table} 
Table 2: Experimental reagents and specifications. EXT\({}_{1}\): CS\({}_{2}\) extract, RAF\({}_{1}\): CS\({}_{2}\) extract; EXT\({}_{2}\): n-hexane extract; RAF\({}_{2}\): n-hexane extract; EXT\({}_{3}\): benzene extract; RAF\({}_{3}\): benzene extract; EXT\({}_{4}\): methanol extract; RAF\({}_{4}\): methanol extract; EXT\({}_{5}\): acetone extract; RAF\({}_{5}\): acetone extract; EXT\({}_{6}\): THF extract; RAF\({}_{6}\): THF extract; EXT\({}_{7}\): THF methanol mixed extract; RAF\({}_{7}\): THF methanol mixed extract.