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.

The different kinds of starch do not take the same tint with the same
quantity of (solid) iodine. That from the potato _arum_ gives a blue, and
that from wheat and rice a violet tint; while the filtrate from starch
paste, from whatever source, always gives a blue color.

* * * * *




THE AMALGAMATION OF SILVER ORES.

DESCRIPTION OF THE FRANCKE "TINA" OR VAT PROCESS FOR THE AMALGAMATION OF
SILVER ORES.

[Footnote: Paper read before the Institution of Mechanical Engineers at
the Cardiff meeting.--_Engineering_.]