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Test for Iodates in Potassium Iodide
1. Aim
To check whether an assigned potassium iodide sample contains iodate impurity using a validated acidified iodide and starch comparison. The current limit and method are to be recorded from the assigned current monograph or approved college method in the student record.
2. Requirements
Assigned potassium iodide, iodate reference, iodide-free starch indicator, specified acid and water, comparison tubes, timer, eye protection, and iodine waste vessel. Exact sample mass, reagent amounts, development time, and acceptance rule are to be recorded from the assigned current monograph or approved college method in the student record.
3. Theory
When iodate and iodide meet under acid conditions, iodine is produced. Starch gives a visible blue response to iodine. In a purity test, the test mixture is compared with a valid blank and iodate reference, so colour may indicate an impurity. The IQ City manual has a contradictory sentence saying absence of blue indicates presence of iodate; that statement conflicts with the described iodine-starch chemistry and must not be used as a decision rule. The controlling monograph resolves the actual acceptance criterion.
4. Procedure
- Find the current potassium iodide monograph and record its iodate impurity method and limit; any absent condition is to be recorded from the assigned current monograph or approved college method in the student record.
- Prepare matched blank, iodate reference, and sample under the specified water and acid conditions.
- Add the approved starch reagent in the validated sequence and start the timer.
- Compare development and intensity at the prescribed time, checking that blank and reference behave as expected.
- Record the actual responses and apply only the verified monograph rule.
5. Calculation, graph, or images as appropriate
| Observation | Actual teaching record |
|---|---|
| KI sample and batch | Record here |
| Iodate standard | Record here |
| Blank response | Record here |
| Reference response | Record here |
| Test colour at specified time | Record here |
| Actual acceptance decision | Record here |
No numerical iodate concentration is fabricated. Assumed observations for practice only: an assumed blank remains colourless, an assumed iodate reference turns blue, and an assumed sample is less blue than the reference. These invented observations illustrate comparison logic, not an actual purity result. Record the real limit from the current assigned monograph. The product decision is made by the qualified reviewer against the assigned current monograph or approved method and recorded in the student record. This page decides nothing: it does not pass, fail, identify, or release any sample.
6. Result
Record the actual result here only when the method and measurements are confirmed. The product decision is made by the qualified reviewer against the assigned current monograph or approved method and recorded in the student record. This page decides nothing: it does not pass, fail, identify, or release any sample. Safety note: Acidified iodide and iodate can release iodine. Work under teaching-lab supervision and collect iodine-containing waste. Do not use a colour impression without a valid reference.
7. References
- Pharmacy Council of India, Pharm.D. Regulations, 2008.
- IQ City Institute of Pharmaceutical Sciences, Presence of Iodate in Potassium Iodide.
- University of British Columbia, Iodate and Iodide Chemistry.
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