Ammonium Iodide is a release agent used in the preparation of XRF fused beads.

ISO Standard 9516 states that:

“7.1.4 If desired, ammonium iodide may be used as a release agent. If it is used, add no more than 0.03 g, prior to fusion”.

An iodide or bromide acts to increase the surface tension of a lithium borate melt. This facilitates the release of the fluid melt from the crucible, ensuring less hang-up of the melt and making crucible cleaning easier. Iodides are a preferable release agent to bromides, since Br Lα interferes with Al Kα.

Beads formed using ammonium iodide tablets have a neutral or positive meniscus, reducing the probability of bead fracture and also reducing sharp edges. Bead curvature, a significant contributor to reading error, is also reduced. Furthermore, the solidified bead releases more freely from the mould to the extent that there is a discernible audible difference, compared to non-iodide bead fusions, therefore demonstrating the stress reduction. As an additional benefit the easy release of beads results in fewer repeats and less mould scratching.

XRF Scientific recommends that the addition of the ammonium iodide tablet should be shortly before pouring (approximately 2 - 4 minutes is considered the most effective).

In summary, use of the ammonium iodide tablets greatly increases the useable life of platinum ware giving a very clean pour, reduces the frequency of repeats and eliminates to a large extent the need for cleaning the crucibles between uses.
 

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