Fire, Arson and Explosives Questions and Answers

Answer: B

API gravity is expressed in degrees.

The American Petroleum Institute gravity is a scale for the density of petroleum liquids relative to water, defined from the specific gravity (SG) at 60°F:

\[ \text{API} = \frac{141.5}{\text{SG}} - 131.5 \]

Values are quoted in degrees API; water is 10°, and lighter oils have higher values. Forensic laboratories use it in characterising petroleum products.

m/s is a speed, and kg/m² and cm³ are a mass per area and a volume, none of them a measure of relative density.

Answer: A

The explosive is TATP.

Triacetone triperoxide is a peroxide explosive made from acetone and hydrogen peroxide. It is notoriously sensitive to friction, impact and heat, which makes it dangerous to handle, and it is very powerful when confined, as in a pipe. Because it is made from household chemicals it has been used in improvised devices.

RDX and PETN are military high explosives that are comparatively insensitive and need a detonator, and ANFO (ammonium nitrate with fuel oil) is a bulk blasting agent that is hard to initiate and not friction-sensitive.

Answer: D

The key gives wavy as the fracture pattern due to heat. Heat fractures of the skull are irregular, with curved or wavy lines, caused by drying and shrinking of the bone.

Radial fractures and hackle marks are features of the way glass breaks, and a spiral fracture comes from twisting force on a long bone. None of those describes a heat fracture. When burnt, the bone dries, shrinks and splits along curved lines, so the fractures do not show a single point of impact or a regular line from a blow, and this is the way an examiner tells a heat fracture from one caused by violence.

Answer: A

HMX is cyclotetramethylene tetranitramine, also called octogen, a powerful high explosive with four nitramine groups in an eight-membered ring. Ammonium nitrate is a different explosive and an oxidiser. Nitroglycerine is glyceryl trinitrate and cyclotrimethylene trinitramine is RDX, so the third and fourth options are other explosives. The answer is A. HMX was made from RDX as a by-product, has a higher melting point and is used in military explosives and in rocket propellants. Its name is said to stand for high melting explosive. The compounds in the other options are not HMX, and the cyclo-trimethylene compound in option D resembles RDX, which is a different explosive.

Answer: C

A hand grenade is not an improvised explosive: it is a manufactured military weapon with a standard fuse, body and filling. Improvised explosive devices are made from available materials.

A pipe bomb is a length of pipe filled with explosive, a letter bomb is an explosive hidden in a postal item, and an acid bulb is a home made delay or chemical device using acid. These are typical improvised devices, so they are not the answer.

Answer: A

The correct matching is antimony sulphide with primer, cordite with double base smokeless powder, gun cotton with nitrocellulose powder and dynamite with nitroglycerine. This is code A, (iv) (iii) (ii) (i). Antimony sulphide is a fuel in primer mixtures. Cordite is made from nitrocellulose and nitroglycerine, so it is double base. Gun cotton is nitrocellulose. Dynamite is nitroglycerine absorbed in an inert material.

Options B, C and D give gun cotton or cordite to the wrong explosive, so they are wrong.

Answer: D

Amatol contains TNT and ammonium nitrate, option D. It is a high explosive mixture of trinitrotoluene and ammonium nitrate, used in shells and bombs, especially in the First and Second World Wars. A mixture of TNT with RDX is called Composition B (A), and TNT with Tetryl (B) or PETN (C) are different mixtures. Amatol was mixed in proportions such as 80 percent ammonium nitrate to 20 percent TNT, which made a cheap explosive for shells.