In a series of experiments we measured the mechanical properties of single alginate beads by means of squeezing experiments between two parallel plates. We used multivalent counter-ions as cross-linking molecules for the formation of three dimensional alginate gels. In this article we examined pure Fe(II) (ferric), Fe(ffl) (ferrous) and Ca(II) (calcium) ions as cross-linking agents and different mixtures between these charged compounds. The results of squeezing experiments showed that capsules formed with pure ferrous ions were less stable than particles which were cross-linked with calcium or ferric ions. It turned out that at equal molar concentrations calcium and ferrous ions formed stronger gels than ferric ions. In addition to squeezing capsule experiments we also investigated different particles by optical microscopy and scanning electron microscopy. Experiments of Energy-dispersive X-ray spectroscopy (EDAX) show different compositions of these beads.
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