Nageli,
Brukner also maintains to be non-existent, and he regards amidulin and
amylodextrin as identical. Brucke gave the name erythrogranulose to a
substance nearly related to granulose, but with a stronger affinity for
iodine, and receiving from it not a blue but a red color. Brukner regards
the red color as resulting from a mixture of erythrodextrin, and the
greater solubility of this substance in water.
If a mixture of filtered potato starch paste and erythrodextrin is dried
in a watch glass covered with a thin pellicle of collodion, and a drop of
iodine solution placed on the latter, it penetrates very slowly through
the pellicle, the dextrin becoming first tinctured with red, and the
granulose afterward with blue. If, on the other hand, no erythrodextrin is
used, the diffusion of the iodine causes at once simply a blue coloring.
With regard to the iodine reaction of starch, Brukner contests Sachsse's
view as to the loss of color of iodide of starch at a high temperature. He
shows that the iodide may resist heat, and that the loss of color depends
on the greater attraction of water for iodine as compared with starch, and
the greater solubility of iodine in water at high temperatures.
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