Which chemical is involved in the Fujiwara Test?

The Fujiwara Test is a qualitative test used in forensic science to identify the presence of certain substances in samples, particularly in cases involving paint or other materials. The test specifically utilizes sodium hydroxide, which plays a crucial role in reacting with the sample to produce distinct color changes. This color change allows forensic analysts to draw conclusions about the composition of the material being tested.

Sodium hydroxide's effectiveness in this test is due to its ability to react with organic compounds and produce a visible reaction, which aids in the identification process. The color produced can indicate the presence of specific substances, thus making it an essential chemical in the Fujiwara Test.

In contrast, other chemicals mentioned in the options, such as hydrochloric acid, ferric chloride, and mercury nitrate, are not typically used in the context of the Fujiwara Test. Each of these chemicals has its own applications in different areas of chemistry and forensic analysis, but they do not play a role in the specific reactions involved in the Fujiwara Test. Therefore, sodium hydroxide is identified as the key chemical related to the test, leading to its selection as the correct answer.