--------+-----------------+
Cane sugar | 1.00 | .. |
Starch | 0.50 | .. |
Gum arabic | 1.33 | 34.72 |
Gum arabic | 1.20 | 43.65 |
Ghatti, 1 | 1.00 | 26.78 |
Ghatti, 2 | 1.33 | 22.86 |
Metarabin | 1.75 | .. |
---------------+--------------------+-----------------+

The amount of reducing sugar calculated as glucose is also appended.
This was estimated in the residue left in the flask after distillation
by Fehling's solution in the usual way. The yields of furfuraldehyde
would appear to have no definite relation to the other chemical data
about a gum, such as the potash and baryta absorptions or the sugar
produced on inversion.

The action of gum solutions upon polarized light is interesting,
especially in view of the fact that arabin is itself strongly
laevo-rotatory [alpha]_{D} = -99 deg., while certain gums are distinctly
dextro-rotatory. Hence it is evident that some other body besides arabin
is present in the gum. We have determined the rotatory power of a number
of gum solutions, the results of which are subjoined. On first
commencing the experiments we experienced great difficulty from the
nature of the solutions. Most of them are distinctly yellow in color and
almost opaque to light, even in dilute solutions such as 5 percent. We
found it necessary first to bleach the gums by a special process; 5
grammes of gum are dissolved in about 40 c.c. of lukewarm water, then a
drop of potassium permanganate is added, and the solution is heated on a
water bath with constant stirring until the permanganate is decomposed
and the solution becomes brown. A drop of sodium hydrogen sulphate is
now added to destroy excess of permanganate. At the same time the
solution becomes perfectly colorless.

It can now be cooled down and made up to 100 c.c., yielding a 5 per
cent. solution of which the rotatory power can be taken with ease. Using
a 20 mm. tube and white light the above numbers were obtained.

----------------+----------------+-----------------
Gum or Dextrin. | Solution used. | [alpha]_{D}
----------------+----------------+-----------------
| Per Cent. |
Aden, 1 | 5 | - 33.8
Cape, 2 | 5 |