A commercially available hydrogenated mixture of fullerenes (HMF) composed of 77% C60Hx and 22% C70Hx has been analyzed by liquid chromatographic analysis (HPLC), electronic absorption, FT-IR spectroscopy, solubility and by thermal analysis (TGA). The results confirm that the HMF is composed by a mixture of C60Hx and C70Hx with a high degree of hydrogenation. The hydrogen content of the HMF was found 6.12% by combustion elemental analysis, suggesting that hydrogenated fullerenes are mixed with hydrogenated fullerene fragments derived from the cage breakdown due to the forcing conditions used in the synthesis (high pressure and high temperature hydrogenation). The HMF is stable in air for a relatively long time of exposure. Under N2, it starts to decompose at 478 degrees C. The maximum decomposition rate under N2 occurs at 522 degrees C. An attempt was made to resolve the C-H stretching band of HMF by recording the FT-IR spectrum at -180 degrees C.