data frame with columns: "ToxCast_chid","DSSTox_Substance_Id",
"DSSTox_Structure_Id","DSSTox_QC.Level",
"Substance_Name","Substance_CASRN",
"Substance_Type","Substance_Note",
"Structure_SMILES","Structure_InChI",
"Structure_InChIKey","Structure_Formula",
"Structure_MolWt"