Investigation of isotopic linkages between raw materials and black powder

The stable isotope analysis of black powder (BP) is of great significance for its comparison and source inference. Previous studies have verified the feasibility of distinguishing different BP samples through stable isotopes. However, the impact of raw materials and synthesis processes on the stable isotopes of BP remains unclear. On the one hand, the raw materials of BP are widely sourced, and whether stable isotopes can distinguish different source materials remains to be studied. On the other hand, the synthesis of BP involves the physical mixing of raw materials, and whether this process leads to isotope fractionation also needs further investigation. To address these problems, stable isotope ratios of 27 charcoals, 15 potassium nitrates, 6 self-made and 10 commercial BP samples were analyzed. The results showed that the stable isotope ratios can be utilized to distinguish charcoals and potassium nitrates from different manufacturers and batches. No significant differences in the nitrogen and oxygen stable isotope ratios between the self-made BP and its raw materials were observed, indicating that the physical mixing process does not induce significant fractionation of stable isotopes. However, the carbon stable isotope ratios of charcoal increased (within 2SD) after being synthesized into BP. Due to the utilization of additives and variations in the synthesis process, the correlation between the stable isotope ratios of commercial BP and its raw materials was complex. The findings of this study provide a scientific reference for tracing the source of BP.