It may be well to state briefly the methods I employed in detecting the
real character of the material. The fibers were first viewed under plain
transmitted light, secondly, polarized light and selenite plate. Since
silk and cotton are polarizing bodies, "cottonized silk," if such could
be made as described, would give, in this case, the prismatic colors of
both fibers, and the complementary colors would differ greatly because of
the great disparity of their respective polarizing and refractive powers.
The fact will be observed that a cotton fiber presents the appearance of
a twisted ribbon when viewed by the microscope, while silk, owing to its
cylindrical form, cannot twist on itself. It should also be considered
that the diameter of "cottonized silk," so called, would be greater than
that of a fiber of silk, because the silk solution would have to be
applied to an actual thread of cotton, and not to a single cotton fiber,
by reason of the shortness of the original hairs of the latter. Were a
single fiber of such a combination put under a suitable objective, and a
drop of nitric acid brought in contact with the fiber, it would be seen
that the acid would destroy the silk and leave the fibers of cotton
untouched, the latter being insoluble in cold nitric acid. The action of
muriatic acid is similar in this respect. Were a fiber of cotton present
and a drop of pure sulphuric acid placed on it, followed quickly by a
drop of a transparent solution of the tincture of iodine, a peculiar
change in the fiber would take place, provided the right proportion of
acid be used. Cotton fiber, and especially flax fiber, under such
conditions, forms into disks or beads of a beautiful blue color.
Fig. 1 represents a cotton fiber, and 2, 3, 4, 5 those of flax, as they
appear under the acid treatment. Every textile amylaceous fiber is
convertible into these forms, more or less, by strong sulphuric acid. The
fibers of cotton, flax, and ramie are examples of amylaceous cellulose,
that is to say, these fibers are converted into starchy matter by
treatment with the last-named acid. Therefore combinations of these
fibers in any composition of non-amylaceous fiber (ligneous or woody
fiber) will be dissolved, leaving the latter unharmed; the woody fibers
remaining will prove suitable objects for examination under the
microscope.