show:

------------+-------------+------------|
Gum. | Z at 18 deg. C. | Z at 50 deg. C.|
------------+-------------+------------|
Gum arabic. | 1016 | 579 |
Gum arabic. | 428 | 228 |
Gum arabic. | 609 | 347 |
Gum arabic. | 581 | 258 |
Ghatti. | 572 | 306 |
Ghatti. | 782 | 418 |
---------------------------------------+

The following table shows the effect of heat upon the viscosity of a
typical Ghatti:

GHATTI GUM NO. 15.--VISCOSITY.

------------+------+-----|
Temperature.| [eta]| Z. |
------------+------+-----|
deg.C. | | |
50 |0.0517| 418 |
46 |0.0581| 468 |
42 |0.0628| 506 |
38 |0.0726| 585 |
34 |0.0788| 635 |
30 |0.0857| 691 |
26 |0.0889| 717 |
22 |0.0919| 741 |
20 |0.0946| 763 |
18 |0.0964| 777 |
------------+------+-----+

There is therefore no essential difference in the behavior of a Ghatti
and a gum arabic on heating. Some interesting results, however, were
obtained by heating gums, both Ghattis and arabics, at a fixed
temperature for the same time, cooling, and then after making the
solutions up to the original volume taking their viscosities at the
ordinary temperature. The effect of heating for two hours to 60 deg. C., 80 deg.
C., or 100 deg. C. was a small permanent alteration in viscosity of the
solution, and it would therefore seem desirable that gum solutions
should be made up cold to get the maximum results. The following numbers
illustrate this change, viz.:

------------------------+-----------+-----------------------+
| | After heating to |
Gum Arabic | Without |-------+-------+-------+
10 Per Cent. | heat. | 60 deg.C. | 80 deg.C. | 100 deg.C |
------------------------+-----------+-------+-------+-------+
Z at 18 deg.C | 570 | 468 | 470 | 517 |
Z at 30 deg.C | 485 | 400 | 422 | 439 |
Z at 50 deg.C | 347 | 287 | 258 | 301 |
Ghatti gum No. 15, | | | | |
5 per cent. Z at 18 deg.C. | 1,104 | 780 | 660 | 758 |
------------------------+-----------+-------+-------+-------+

The variation of viscosity wi