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Winkler's Iodometric Method

Water, of all the natural substances, comes closest to being the universal chemical solvent. This remarkable property makes it one of the most important components of all living organisms. Oxygen forms one of the abiotic factors governing the physiological and ecological operations of both plants and animals. It is the aerobic respiration that has been preferred by the living organisms as against anaerobic perhaps to oxidize the calorific compounds and mobilize energy. Thus oxygen becomes an indispensable factor for bodily metabolisms. Oxygen gets diffused in aquatic bodies from the atmosphere while the strength of oxygen in the system is enriched by the photosynthetic activities of phytoplanktons and regular hydrophytes. A minimum of 4 ppm [4 parts per million] of oxygen is required in the dissolved state to maintain and keep balance of the aquatic population. However, the amount of oxygen varies in water bodies according to its geographical location and usage. To know the normal fluctuation of oxygen in the water bodies, its quantitative estimation using Winkler's iodometric method at regular intervals is found to be significant.

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Glassware - Stoppered sample bottles [300ml], Pipettes, Burette, Conical flask, Measuring jars.
Reagents -
1. 0.025N Sodium thio sulphate [Na2S2O3. 5H2O]
{Also known as hypo by photographers, is colorless and odorless. 24.82 g of Na2S2O3. 5H2O is dissolved in distilled water and made up to a volume of 1l. This solution is stabilized by the addition of a pellet of Sodium hydroxide [NaOH] or 0.4 g Borax. This forms the stock solution of 0.1N. This solution is diluted four times to obtain 0.025N solution and has to be stored in a brown glass bottle.}
2. Alkaline ...

Solution Summary

This solution explains Winkler's iodometric method to analyze dissolved oxygen content in various samples of water.