Which test is done to find out the presence of free chlorine and chloramines in water?

Appeared in: AIIMS Raipur NO- 2019 (shift 3rd)

Explanation

The Orthotolidine (OT) test is the correct method for determining the presence of both free chlorine and combined chlorine (chloramines) in water.
It works via a colorimetric reaction; the Orthotolidine reagent turns yellow in the presence of chlorine, and the color's intensity indicates the concentration.
The test can differentiate between chlorine types based on reaction time. Free chlorine reacts instantly (within 10 seconds), while combined chlorine reacts slowly (taking 15-20 minutes).
A modification, the Orthotolidine-Arsenite (OTA) test, can be used for more precise, separate measurements of free and combined chlorine.

Option B: Breakpoint chlorination is a term for a water treatment process, not a diagnostic test. It describes the point at which the chlorine demand of water is met.
Option C: Chlorination is the general name for the process of adding chlorine to water for disinfection.
Option D: Bleaching powder is a chemical substance (calcium hypochlorite) that is used to disinfect water. It is a source of chlorine, not a test to measure it.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Water quality testing for residual chlorine as background academic context rather than a clinical decision trigger.
As a community health nurse, understanding water purification and testing is crucial for preventing waterborne diseases like cholera, typhoid, and dysentery.
Nurses play a key role in educating communities about safe drinking water practices, including methods for household water purification and the importance of maintaining clean water sources.
What if? If a water sample is highly turbid (cloudy), the Orthotolidine test results can be inaccurate. In such a case, the nurse should advise that the water must be filtered or allowed to settle before disinfection and testing to ensure effectiveness.

How to Approach the Question

First, identify the core of the question. The keyword here is 'test'. The question is asking for a method used to measure or detect something.
Analyze the options to see which one is a 'test' versus a 'process' or a 'substance'.
Option A, 'Orthotolidine test', explicitly includes the word 'test'.
Options B ('Breakpoint chlorination') and C ('Chlorination') describe processes related to water treatment.
Option D ('Bleaching powder') is a chemical substance.
Based on this analysis, the only option that is a test is the Orthotolidine test, making it the most logical answer.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart B (pp 233-449 of 464) p. 32-34

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