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Iodine Testing

Established in 1956, Midwest Microlab, LLC, is equipped to provide rapid accurate organic microchemical analysis to research and industry. Specialties include analysis for Carbon, Hydrogen, Nitrogen, direct Oxygen, and halogens including Fluorine.

What is Iodine?

Iodine (from the Greek word Iodes, meaning "violet"), is a chemical element in the periodic table that has the symbol I and atomic number 53. Chemically, iodine is the least reactive of the halogens, and the most electropositive halogen after astatine. Iodine is primarily used in medicine, photography and dyes. It is required in trace amounts by most living organisms.

 

As with all other halogens (members of Group VII in the Periodic Table), iodine forms diatomic molecules, and hence, has the molecular formula of I2.

 

Iodine is a dark-gray/purple-black solid that sublimates at standard temperatures into a purple-pink gas that has an irritating odor. This halogen forms compounds with many elements, but is less active than the other members of its Group VII (halogens) and has some metallic-like properties. Iodine dissolves easily in chloroform, carbon tetrachloride, or carbon disulphide to form purple solutions (It is only slightly soluble in water, giving a yellow solution). The deep blue color of starch-iodine complexes is produced only by the free element.

 

Many students who have seen the classroom demonstration where iodine crystals are gently heated in a test tube come away with the impression that liquid iodine cannot exist at atmospheric pressure. This misconception arises because sublimation occurs without the intermediacy of liquid. The truth is that if iodine crystals are heated carefully to their melting point of 113.7 °C, the crystals will fuse into a liquid, which will be present under a dense blanket of the vapor.


 

Relevant sites for Iodine:

 

Organic Iodine(I, III, and V) Chemistry: 10 Years of Development ...
A full list of our papers dealing with the organic iodine(I, ... So far, nine organic iodine(III) compounds have been used as the oxidants for the oxidative ...

 

International Union of Pure and Applied Chemistry

In addition, marine plants and animals have provided a rich source of varied and unexpected organic iodine compounds that occur, along with other organic ...

 

Chemistry and the Aquarium
These results are indicative of total iodine (iodide + iodate + organic iodine) ... Dissolved organic iodine in marine waters: Determination, occurrence and ...

 

Iodine chemistry and its role in halogen activation and ozone loss ...

Other aqueous-phase species are only temporary reservoirs and can be re-activated to yield gas phase iodine. Assuming release rates of the organic iodine ...

 

Potassium iodide - Wikipedia, the free encyclopedia

KI is often used as a source of iodide ion in organic synthesis. A useful application is in the preparation of aryl iodides from arenediazonium salts[5], ...

 

Iodine: The Universal Nutrient Article

“When I was a medical student, iodine in the form of KI was the universal medicine. ... it was incorporated into the toxic organic iodine-containing drugs. ...

Elemental AnalysisOur Laboratory

Iodine Determination via Schoeniger Combustion:

The  solid sample is weighed into ashless paper and inserted into custom made Platinum stopper.  The stopper is fitted it a flask that is charged with the appropriate absorbants  and oxygen.  On combustion the Iodine present is trapped in several forms..free iodine and Iodate.  The gasses are absorbed on the liquids.  The resulting liquid is treated with various reactants to convert all remaining Iodine to the form of Iodate. The resulting liquid is then titrated with a standardized solution of Sodium thiosulfate

A standard starch titration yields a color change of black to clear at the endpoint.  Other halogens do not seem to interfere in the determination. Selenium does seem to show some interference.
           
The most common standard for this determination is Potassium Bi-Iodate and Para-Iodo-Benzoic Acid from the NIST.  There are others that may be used on occasion.

The preceding is a brief description of our techniques used in the determination of iodine.

This can be a time consuming and labor intensive determination, therefore: we cannot usually guarantee a 24 hour “rush” turnaround for this work.

 

Click here for CHN Analysis White PaperClick here for an article regarding CHN analysis in the 21 century. Requires Adobe Acrobat Reader

 

Established in 1956, Midwest Microlab, LLC, is equipped to provide rapid accurate organic microchemical analysis to research and industry. Specialties include analysis for Carbon, Hydrogen, Nitrogen, direct Oxygen, and halogens including Fluorine.