What is the iodine number?

The iodine number is the milligrams of iodine adsorbed per gram of activated carbon. Because the iodine molecule is small, it mainly reflects micropore volume below 2 nm.

What iodine number is good?

Below 600 mg/g is low, 800–900 mg/g is mid-grade, and 1000 mg/g or above is high grade. Standard coconut carbons imported into Türkiye typically sit at 600–700 mg/g; Akarbon's range includes models at 1000 mg/g.

How is the iodine number tested?

By ASTM D4607: an iodine solution of known concentration is contacted with the carbon, the residual iodine is titrated, and the difference gives the adsorbed amount.

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Iodine Number Explained

The number buyers check first: what it measures, how it is tested, and which values count as good.

What it measures

The iodine number is the amount of iodine adsorbed by one gram of activated carbon under standard conditions, expressed in mg/g. The iodine molecule is small, so the figure mainly reflects micropore volume — pores below 2 nm.

In practice it is the fastest answer to "how much will this carbon hold?". It is not directly proportional to surface area, but it correlates strongly — and in liquid-phase applications it is the single most telling indicator of micropore performance.

How it is measured

Testing follows ASTM D4607: an iodine solution of known concentration is contacted with ground carbon, the remaining iodine is found by titration, and the difference gives the adsorbed amount.

Grinding and drying of the sample affect the result, so figures are only comparable when obtained by the same method. We test per batch; documents are on the technical data sheets page.

What counts as good?

Roughly: below 600 mg/g is low, 800–900 mg/g is the commercial middle, and 1000 mg/g or above is high grade. The standard coconut shell carbons imported into Türkiye typically sit at 600–700 mg/g, while Europe and the United States generally specify products around 1000.

Akarbon's hazelnut shell range includes models at 1000 mg/g — clearly above the standard imported coconut grades. The figure holds for both the granular and powdered forms.

Is it enough on its own?

No. The iodine number only describes micropores. Large molecules — colour bodies, humic acids — are held in mesopores, and that is what methylene blue indicates: ours is 100–250 mg/g, specified to order.

Read the four together when deciding: iodine number, methylene blue, ash and moisture. To see how the pores actually work, visit what is activated carbon.