Time of Firing


  • After recent discharge a black deposit of potassium sulphide mixed with carbon is found in the barrel of the firearm, if black gunpowder was used. Up to five or six hours this deposit forms a strongly alkaline solution when dissolved in distilled water and emits an offensive odour of sulphuretted hydrogen. If the solution is filtered, and the filtrate is treated with a solution of lead acetate, a black precipitate of lead sulphide is formed. After exposure to air and moisture for a few days the potassium sulphide becomes converted into thiosulphate, thiocyanate and finally potassium sulphate, that gives a neutral solution with distilled water that gives a white precipitate with lead acetate. Later, oxides of iron (iron rust) with traces of iron sulphate are formed in the barrel.
  • Smokeless nitro-powders leave a dark grey deposit in the barrel of a recently discharged firearm. It does not change with the lapse of time, gives a neutral solution with distilled water, and contains nitrites and nitrates, but not sulphides. If chromate or bichromate powder is used, the residue in the barrel is usually of a greenish tint.
  • It should be borne in mind that the composition of the deposit will vary considerably if the firearm was dirty at the time of its discharge, and a veterinarian has no means to know its condition prior to discharge. Again, a deposit would not be found if the weapon had been thoroughly cleansed after discharge.
Last modified: Tuesday, 5 June 2012, 11:48 AM