2,021 | 449
Mixture F | 15 | 1,930 | 787
Mixture E | 11.3 | 2,058 | 3,919
-----------+------+-------------+-------------

While performing these experiments, an attempt was made to obtain an
"ash-free" gum, in order to compare its viscosity with that of the same
gum in its natural state. A gum low in ash was dissolved in water, and
the solution poured on to a dialyzer, and sufficient hydrochloric acid
added to convert the salts into chlorides. When the dialyzed gum
solution ceased to contain any trace of chlorides, it was made up to a
10 per cent. solution, and its viscosity determined under 100 mm.
pressure, giving the following results at 15 deg. C.:

-----------------+--------------+-----
-------- | [eta] | Z
-----------------+--------------+-----
Natural gum..... | 0.05570 | 449
"Ash-free" gum.. | 0.05431 | 438
-----------------+--------------+-----

Thus showing that the viscosity of pure arabin is almost identical with
that of its salts in gum.

The yield of furfuraldehyde by the breaking down of arabin and metarabin
was thought possibly to be of some value in differentiating the natural
gums from one another, but we have not succeeded in obtaining results of
much value. 0.2 gramme of a gum were heated with 100 c.c. of 15 per
cent. sulphuric acid for about 21/2 hours in an Erlenmeyer flask with a
reflux condenser. After this period of time, further treating did not
increase the amount of furfuraldehyde produced. The acid liquid, which
was generally yellow in color, was then cooled and neutralized with
strong caustic soda. The neutral or very faintly alkaline solution was
then distilled almost to dryness, when practically the whole of the
furfuraldehyde comes over. The color produced by the gum distillate with
aniline acetate can now be compared with that obtained from some
standard substance treated similarly. The body we have taken as a
standard is the distillate from the same weight of cane sugar. The tint
obtained with the standard was then compared with that yielded by the
gum distillate from which the respective ratios of furfuraldehyde are
obtained. The following table shows some of these results:

---------------+--------------------+-----------------+
| Comparative Yield | Amount of |
Substance. | of Furfuraldehyde. |Glucose Produced.|
---------------+------------