sity enormously.

We next tried a series of similar experiments with a Ghatti containing
far less insoluble residue and which consequently would require less gum
arabic to produce a perfect solution. Mixtures were made in the
following proportions, viz.:

----------------------+------------+-----------+
----- | 13.3 per Cent. Ghatti. |
----------------------+------------+-----------+
F. Pressure 200 mm. | [eta] | Z. |
Temperature 15 deg. C. | 0.0976 | 787 |
----------------------+------------+-----------+

----------------------+------------+-----------+
----- | 86.6 per Cent. Ghatti. |
----------------------+------------+-----------+
G. Pressure 200 mm. | [eta] | Z. |
Temperature 15 deg. C. | 0.4336 | 3,497 |
----------------------+------------+-----------+

This latter solution is approaching fairly closely to our "maximum
viscosity" with the previous Ghatti, and probably a very slight decrease
in the amount of gum arabic would bring about the required increase in
viscosity.

When these experiments were first commenced we were still under the
impression, which several months' experience of working with gums had
produced, namely, that the Ghattis were quite distinct in their
properties to ordinary gum arabics. But the new hypothesis, and the
experiments undertaken to confirm it, showed clearly that if the
viscosity of a gum solution depends on the ratio of metarabin to arabin,
then there is no absolute line of demarkation between a Ghatti and a gum
arabic. In other words, there is a constant gradation between gum arabic
and Ghattis, down to such gums as cherry gum, consisting wholly of
metarabin and quite insoluble in water. Therefore those gum arabics
which are low in viscosity consist of nearly pure arabin, while as the
viscosity increases so does the amount of metarabin, until we come to
Ghattis which contain more metarabin than their arabin can hold in
solution, when their viscosity goes down again.

From these observations it would follow, that by taking a gum of less
viscosity than the gum arabic previously used to dissolve the Ghatti,
less of it would be required to do the same work. We confirmed this
suggestion experimentally by taking another gum arabic of viscosity
0.0557 at 15 deg. C. A mixture containing 93.3 per cent. of this Ghatti and
6.7 per cent. of our thinnest g