Iodine (I) Determination by Schoniger Combustion (Oxygen Flask Combustion Method) (CAT#: STEM-EA-0004-ZJF)

The Schoniger combustion (also known as the oxygen flask combustion method) is a method of elemental analysis first developed by Wolfgang Schoniger in 1955.
The test is conducted in an Erlenmeyer flask or a separatory funnel. A sample is burned in pure oxygen, and then the combustion products are absorbed by sodium hydroxide solution. According to its definition, the oxygen flask combustion method is useful for identifying or determining whether sulphur or halogens are produced when organic compounds are burned. Compounds like these contain iodine, fluorine, bromine, chlorine, or sulphur in a flask containing oxygen. Combustion of these compounds produces inorganic products that are soluble in water. As a result of this process, the inorganic materials produced are determined to be bound for each element. Extreme care should be taken when performing the test. Any organic solvent must be completely removed from the flask before use.

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1. Upon receiving the solid sample, it is weighed into ashless paper and placed into a platinum stopper that has been custom made.
2. The stopper is fitted in a flask containing the appropriate absorbents and oxygen. As a result of combustion, the iodine present is trapped in several forms, including free iodine and iodate.
3. Gases are absorbed by liquids. Various reactants are used to convert all remaining iodine in the liquid to the form of iodate.
4. The liquid is then titrated with a standardized solution of sodium thiosulfate. At the end of a standard starch titration, the color changes from black to clear.

• Oxygen flask combustion apparatus
• Sample material

1. It appears that other halogens do not interfere with the determination, although selenium appears to interfere.
2. The determination process can be time-consuming and labor-intensive.