**Question:** Double based smokeless gun powder consists of

A. nitrocellulose
B. nitroglycerin
C. guncotton
D. pyrodex

**Correct Answer:** Double based smokeless gun powder consists of nitrocellulose and nitroglycerin (Option B and D).

**Core Concept:** Smokeless gunpowder, also known as blackpowder substitute, is used primarily in firearms to create an explosion for propulsion. It is a safer alternative to black powder that was historically used due to its smoke and unpredictable performance.

**Why the Correct Answer is Right:** Double based smokeless gunpowder is composed of two components:

1. **Nitrocellulose (Option A):** Derived from cellulose, nitrocellulose is a polymer that undergoes decomposition when mixed with nitric acid and nitroglycerin. The nitric acid helps to convert cellulose into nitrocellulose. This component forms the base of the smokeless gunpowder mixture.
2. **Nitroglycerin (Option D):** A highly sensitive, unstable liquid derived from glycerol, nitroglycerin is a precursor to nitrocellulose. When mixed with nitrocellulose, it forms a stable mixture.

**Why Each Wrong Option is Incorrect:**

3. **Guncotton (Option C):** Guncotton is an explosive mixture of nitrocellulose and nitroglycerin, not used in gunpowder production.
4. **Pyrodex (Option D):** Pyrodex is a modern smokeless gunpowder composition, consisting mainly of a pyrolytic nitrocellulose and propellants, not the traditional nitrocellulose and nitroglycerin.

**Clinical Pearl:** Smokeless gunpowder provides more consistent performance, reduced smoke, and improved safety compared to the traditional black powder. It is used in firearms to ensure the firearm can function reliably and safely. Understanding the composition of smokeless gunpowder is crucial for firearm enthusiasts, gunsmiths, and history buffs alike, as it has significantly impacted firearms development and safety standards.