Which of the following carbon compounds has been widely used as a fire extinguisher, especially for liquid and electrical fires?

Introduction / Context:
This question tests your knowledge of applied chemistry, specifically the use of certain carbon compounds in fire safety. Different fire extinguishing agents are suited to different classes of fire. Some organic liquids were historically used in extinguishers, particularly for electrical and liquid fuel fires. You are asked to identify which carbon compound among the options has been widely used as a fire extinguisher.

Given Data / Assumptions:

• The options are carbon disulphide, chloroform, carbon tetrachloride and methylene chloride.
• The compound in question should have properties suitable for extinguishing certain types of fire.
• It should be non flammable, able to interrupt the combustion process and preferably not conduct electricity.
• Historical usage in fire extinguishers is relevant, even though safety concerns have changed modern practice.

Concept / Approach:
Carbon tetrachloride (CCl4) is a non flammable, dense liquid that was historically used in fire extinguishers, especially for liquid fuel and electrical fires. When sprayed onto flames, it vaporises, displacing oxygen and interfering with the free radical chain reactions that sustain combustion. It is also a non conductor of electricity, which made it suitable for electrical equipment fires. However, it is toxic and can form harmful phosgene gas at high temperatures, so its use has been discontinued in many countries. The other compounds listed either are flammable or have other uses, not primary fire extinguishing roles.

Step-by-Step Solution:
Step 1: Recall that carbon tetrachloride is a chlorinated hydrocarbon once used in portable fire extinguishers. Step 2: It is non flammable and can form a heavy vapour blanket over burning liquids, cutting off oxygen supply. Step 3: It also does not conduct electricity, so it was considered suitable for fires involving electrical equipment. Step 4: Carbon disulphide, in contrast, is highly flammable and would not be used as a fire extinguishing agent. Step 5: Chloroform and methylene chloride have roles as solvents and anaesthetics or degreasers, not as standard fire extinguishing liquids. Step 6: Therefore, the correct answer is carbon tetrachloride.

Verification / Alternative check:
If you look at older descriptions of fire safety equipment, you will find references to carbon tetrachloride extinguishers, which were common before the health risks became widely known. These devices often contained glass bulbs filled with carbon tetrachloride that would burst when thrown at a fire. Modern fire safety guidelines no longer recommend carbon tetrachloride due to toxicity, and safer halogenated compounds or dry chemical powders are used instead. This historical information confirms that among the listed options, carbon tetrachloride is the compound associated with fire extinguishing use.

Why Other Options Are Wrong:
Carbon disulphide is very flammable and is actually a fire hazard, not a fire extinguisher. Chloroform has been used as an anaesthetic and solvent but is not a standard extinguishing agent. Methylene chloride, also called dichloromethane, is used as a solvent and paint stripper and has its own health risks, but it has not been widely adopted as a fire extinguisher fluid. None of these alternatives meets the historical and practical role of carbon tetrachloride in fire suppression.

Common Pitfalls:
Students may incorrectly assume that any chlorinated solvent could be a fire extinguishing agent because chlorinated compounds are often non flammable. However, not all such compounds have been used for this purpose, and toxicity and decomposition products must be considered. Another pitfall is to focus on the word carbon in the name and ignore the halogens attached. The correct approach is to recall specific compounds that have documented fire safety applications. Remember that carbon tetrachloride has largely been phased out due to health concerns but remains a classic example in examination questions.

Final Answer:
The carbon compound widely used in older fire extinguishers is carbon tetrachloride.