um arabic gave a clear solution which had
the highest viscocity we have yet obtained for a 10 per cent. solution.

----------------------+--------+-------+
H. Pressure 200 mm. | [eta] | Z. |
Temperature 15 deg. C. | 0.5525 | 4,456 |
----------------------+--------+-------+

This gum arabic may be regarded as nearly pure arabin (as calcium and
potassium, etc., salt). By diluting the new "maximum viscosity"
solution, therefore, with the 10 per cent. solution of the gum arabic in
fixed proportions we obtain a series of viscosities which are shown in
the following curve.

[Illustration: Curve Showing Influence of Ghatti upon Viscosity.]

Besides obtaining this curve for change in viscosity from maximum amount
of metarabin to no metarabin at all, we also traced the decrease in
viscosity of the "maximum" solution by dilution with water. The
following numbers were thus obtained, and plotted out into a curve.

Having obtained this curve, we are now in a position to follow up the
hypothesis by calculating the surplus amount of insoluble matter in a
Ghatti. For, let it be conceded that the solution of any Ghatti leaving
an insoluble residue is a mixture of arabin and metarabin in the same
ratio as our "maximum" solution, only more diluted with water, then from
the found viscosity we obtain a point on the curve for dilution, which
gives the percentage of dissolved matter.

Now to show the use of this: The Z value for a 10 per cent. solution of
the second Ghatti at 15 deg. C. is 2,940. This corresponds on the curve to
8.4 dissolved matter. 10 - 8.4 = 1.6 grammes in 10 grammes, which is
insoluble.

CHANGE OF VISCOSITY WITH DILUTION--"MAXIMUM" SOLUTION. 15 deg. C.
TEMPERATURE.

------------+--------------+---------
Percentage. | [eta] | Z.
------------+--------------+---------
10 | 0.55250 | 4,456
9 | 0.42850 | 3,456
8 | 0.35120 | 2,832
7 | 0.27660 | 2,230
6 | 0.22290 | 1,797
5 | 0.16810 | 1,355
4 | 0.11842 | 955
3 | 0.08020 | 647
2 | 0.06190 | 499
1 | 0.03610 | 291
------------+--------------+---------

[Illustration: Curve of Variation in Viscosity on Dilution of the
"Maximum" Solution.]

We have already shown that a "maximum" viscosity solution of t