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. 2021 Aug 24;6(35):22848-22856.
doi: 10.1021/acsomega.1c03380. eCollection 2021 Sep 7.

Evolution of Medieval Gunpowder: Thermodynamic and Combustion Analysis

Tessy S Ritchie  1 , Kathleen E Riegner  2 , Robert J Seals  3 , Clifford J Rogers  3 , Dawn E Riegner  1
Affiliations

Evolution of Medieval Gunpowder: Thermodynamic and Combustion Analysis

Tessy S Ritchie et al. ACS Omega. .

Abstract

Medieval gunpowder recipes of potassium nitrate (KNO3), charcoal (C), and sulfur (S8) were investigated by bomb calorimetry to determine their enthalpies of combustion and by differential scanning calorimetry (DSC) to determine their pre-ignition and propagative ignition enthalpies. Various sample preparation methods and several additional ingredients were also tested to determine any effects on the thermodynamic values. Gunpowder recipes were prepared and used in a replica cannon that was manufactured and operated according to medieval records. Post-firing residues were collected from the bomb calorimeter and the cannon in efforts to further characterize recipe energetics using DSC. In general, during the period of 1338-1400, the %KNO3 increased, and heats of combustion decreased, while between 1400 and 1460, the %KNO3 decreased, and heats of combustion increased. However, since KNO3 was usually found in the post-bomb calorimetry and post-cannon firing residues, it was not the limiting reactant. The highest pre-ignition and propagative ignition energies occurred when the KNO3:S8 ratio was 3:1 as determined by DSC, and the highest enthalpies of combustion were measured for recipes where the KNO3:C ratio was 1:1 as determined by bomb calorimetry.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
(A) Medieval gun, shot, and powder charge masses; (B) gunpowder KNO3, S8, and C mass percentages.
Figure 2
Figure 2
Heats of combustion for each recipe in chronological order.
Figure 3
Figure 3
Effect of serpentine recipe compositions on (A) bomb calorimetry heats of combustion and (B) DSC enthalpies from the first heat cycle.
Figure 4
Figure 4
First heat DSC overlays for recipes 2B and 3A.
Figure 5
Figure 5
Comparison of combustion enthalpies when various corning additives are used.
Figure 6
Figure 6
First heat DSC overlays of (A) 1-E and (B) 4-C recipes without varnish and the same recipes with varnish (1-E-i and 4-C-i).
Figure 7
Figure 7
First heat DSC overlays indicating effects of adding (A) brandy to recipe 2-C and adding (B) vinegar to recipe 2-B.
Figure 8
Figure 8
First heat DSC overlays indicating effects of adding (A) camphor and ammonium chloride to recipe 3-A and adding (B) camphor and quicklime to recipe 3-B.
Figure 9
Figure 9
(A) Pre- and (B) post-1400 ingredient ratios and their impact on heats of combustion.
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References

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    1. Adapted from

    2. Rogers C. J.Gunpowder Artillery in Europe, 1326-1500: Innovation and Impact, Technology, Violence and War. Essays in Honor of John F. Guilmartin, Jr.; Brill: Leiden, 2019, 39–71.

    3. Figure 2.1