his gum is
formed when 6.7 per cent, of thin gum arabic is added to it, and
therefore 6.7 parts of a thin gum arabic are required to bring 16 parts
of metarabin into solution. A convenient rule, therefore, in order to
obtain complete solution of a Ghatti gum is to add half the weight in
thin gum of the insoluble metarabin found from the viscosity
determination. But the portion of the gum which dissolved is made up in
a similar manner (being a diluted "maximum" solution).

Therefore the 84 per cent. of soluble matter contains 58 parts of
metarabin, and the total metarabin in this gum is 58 + 16 = 74 per cent,
on the dry gum.

With these solutions of high viscosity some other work was done which
may be of interest. The temperature curves of the mixtures marked E, G,
and F were obtained between 60 deg. C. and 15 deg. C. The two former curves
showed a direction practically parallel to that at the 10 per cent.
solutions, and as they were approaching to the "maximum" solution, this
is what one would expect. Mr. S. Skinner, of Cambridge, was also good
enough to determine the electrical resistances of these solutions and
the Ghattis and gum arabics employed in their preparation. The
electrical resistance of these gum solutions steadily diminishes as the
temperature increases, and the curve is similar to those obtained for
rate of change with temperature. Although the curves run in, roughly,
the same direction, there does not appear to be any exact ratio between
the viscosities of two gums say at 15 deg. C. and their electrical
resistances at the same temperature; hence it would not seem possible to
substitute a determination of the electrical resistance for the
viscosity determination. The results appear to be greatly influenced by
the amount of mineral matter present, gums with the greatest ash giving
lower resistances.

Experiments were conducted with two Ghattis and two gum arabics, besides
the mixtures marked E, F, and H. Comparison of the electrical
resistances with the viscosities at 15 deg. C. shows the absence of any
fixed ratio between them.

-----------+------+-------------+------------
Gum or | deg.C. | Ohms | Z Viscosity
Mixture. | | Resistance. | at 15 deg. C.
-----------+------+-------------+-------------
Ghatti, 1 | 10 | 5,667 | 1,490
Ghatti, 2 | 15 | 2,220 | 2,940
Arabic 1 | 15 | 1,350 | 605
Arabic 2 | 10 |