Since no solution is obtained from uninjured
grains, even after soaking for weeks in water, Brukner concludes that the
outer layers of the starch grains form a membrane protecting the interior
soluble layers from the action of the water.
The soluble filtrate from starch paste also contains a substance identical
with granulose. Between the two kinds of starch, the granular and that
contained in paste, there is no chemical but only a physical difference,
depending on the condition of aggregation of their micellae.
W. Nageli maintains that granulose, or soluble starch, differs from
amylodextrin in the former being precipitated by tannic acid and acetate
of lead, while the latter is not. Brukner fails to confirm this
difference, obtaining a voluminous precipitate with tannic acid and
acetate of lead in the case of both substances. Another difference
maintained by Nageli, that freshly precipitated starch is insoluble,
amylodextrin soluble in water, is also contested; the author finding that
granulose is soluble to a considerable extent in water, not only
immediately after precipitation, but when it has remained for twenty-four
hours under absolute alcohol. Other differences pointed out by W.
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