Practice

Forensic Chemistry: Explosives, Fire Debris and Arson Analysis

This mock covers the chemistry, instrumentation and statutory framework of explosives, fire-debris and arson analysis as it appears in the FACT Forensic Chemistry II syllabus, the NFSU MSc Forensic Science papers, and the UGC-NET Forensic Science Paper II. Thirty medium-difficulty questions across the classification of explosives — low (deflagration < 1000 m/s) versus high (detonation > 1000 m/s with a true shock wave), primary versus secondary versus tertiary, military versus commercial — and the chemistry of the compounds an FSL meets in casework: TNT (2,4,6-trinitrotoluene), RDX (cyclotrimethylenetrinitramine), PETN (pentaerythritol tetranitrate), HMX, ANFO, nitroglycerine, picric acid and the peroxide-based improvised explosive TATP that has dominated 21st-century IED casework. It then drills into pre-blast and post-blast detection: the modified Greiss test (the pink-red azo dye for nitrites and nitrated species after reduction), diphenylamine in concentrated sulphuric acid for nitrate / nitrite, ion mobility spectrometry (IMS) for trace airport screening, HPLC-UV, GC-MS in negative-ion chemical ionisation (NICI) for nitramines and nitrate esters at sub-nanogram levels, FTIR / ATR-FTIR and Raman for non-destructive bulk identification, ion chromatography for inorganic anions and cations from ammonium-nitrate and urea-nitrate residues, and SEM-EDX for particle-by-particle elemental confirmation of black-powder and flash-powder residues. The mock also covers fire-debris analysis under the ASTM E1412 (passive-headspace adsorption onto activated charcoal) and ASTM E1618 (GC-MS classification into Gasoline / LPD / MPD / HPD / iso-paraffinic / naphthenic-paraffinic / aromatic / n-alkane / oxygenated / miscellaneous) workflow, the diagnostic-ion (m/z 57, 91, 105, 117, 128, 142, 156) extracted-ion-chromatogram analysis that suppresses pyrolysis interferences from carpet, foam and wood, the fire tetrahedron, and the modern NFPA 921 consensus that visual char patterns alone are not reliable arson indicators. It is pitched at first- and second-year MSc Forensic Science students at NFSU, LNJN-NICFS and other Indian universities, FACT and FACT Plus aspirants, and UGC-NET candidates. Themes covered: - Low vs high explosives — deflagration vs detonation, the 1000 m/s threshold - Primary, secondary and tertiary sensitivity classes; the explosive train - TNT, RDX, PETN, HMX, ANFO, nitroglycerine, picric acid, TATP — chemistry and analysis - Pre-blast detection: Greiss, diphenylamine, IMS, HPLC, GC-MS NICI, FTIR, Raman - Post-blast residue analysis: sampling, control samples, sub-microgram detection limits - SEM-EDX for inorganic residues; ion chromatography for ammonium, nitrate, chlorate - Fire chemistry: combustion, pyrolysis, the fire tetrahedron, the chain-reaction element - ASTM E1618 ignitable-liquid classes (gasoline, LPD, MPD, HPD, etc.) - Diagnostic-ion EIC analysis — m/z 57 alkanes, 91 aromatics, 117 indanes, 128/142/156 naphthalenes - ASTM E1412 passive-headspace adsorption with activated charcoal; container choice (metal cans, Teflon-lined glass, nylon-11 Kapak) - NFPA 921 origin-and-cause; the limits of visual char-pattern interpretation - Indian statute: Explosives Act 1884 (regulatory, PESO licensing), Explosive Substances Act 1908 (criminal — Sections 3 / 4 / 5 / 6), BNS 2023 mischief-by-fire provisions Each question carries a detailed 220+ word explanation citing the standard references — Saferstein's Criminalistics (12th edition), Beveridge's *Forensic Investigation of Explosions* (2nd edition, CRC Press 2012), Yinon's *Forensic and Environmental Detection of Explosives* (Wiley 1999), Stauffer, Dolan and Newman's *Fire Debris Analysis* (Academic Press 2008), ASTM E1412 and ASTM E1618, ASTM E1492 on evidence handling, NFPA 921 (current edition), the Explosives Act 1884 with the Explosives Rules 2008, and the Explosive Substances Act 1908. Allow 15 minutes; the explanations are long enough to use as study notes by themselves. If you can pass this mock comfortably, you have the FACT Forensic Chemistry II explosives-and-arson layer that the case-law and instrumental-techniques papers build on.