Senegal............. | 0.0627 | 0.0557 | 364 Gum arabic.......... | 0.0511 | 0.0430 | 285 Water............... | 0.0149 | 0.0124 | 100 Ghatti.............. | 0.2903 | 0.2880 | 2,322 Ghatti, 5 per cent.. | 0.0903 | 0.0828 | 688 Ghatti, 5 per cent.. | 0.1391 | 0.1350 | 1,089 Ghatti, 5 per cent.. | 0.1795 | 0.1760 | 1,420 Ghatti, 5 per cent.. | 0.1527 | 0.1485 | 1,198 Ghatti, 5 per cent.. | 0.1139 | 0.1083 | 873 Ghatti, 5 per cent.. | 0.1419 | 0.1369 | 1,104 Dextrin............. | 0.0398 | 0.0255 | 169 Dextrin............. | 0.0341 | 0.0196 | 129 Dextrin............. | 0.0455 | 0.0380 | 306 Gum substitute...... | 0.0318 | 0.0224 | 180 Gum substitute...... | 0.0318 | 0.0224 | 180 Amrad............... | 0.0793 | 0.0708 | 570 Australian.......... | 0.0378 | 0.0283 | 228 Australian.......... | 0.0365 | 0.0268 | 216 Brazilian........... | 0.0668 | 0.0627 | 506 Brazilian........... | 0.0516 | 0.0445 | 359 Ghatti.............. | 0.3636 | 0.3621 | 2,920 ---------------------+--------------+------------+----------

In the column for [eta] corrected the differences due to the use of different instruments are of course eliminated.  The absolute viscosity of water at 15 deg.  C. determined in four different instruments is shown below.  Poiseuille’s value for water being 0.0122.

--------------+-------------+-------------+------------

-+-------------+
Instrument. |      1.     |      2.     |      3.     |      4.     |
--------------+-------------+-------------+-------------+---

----------+
[eta] corrtd. |      0.0109 |     0.01185 |      0.0124 |      0.0120 |
of water. |             |             |             |             |
K_{1} value.. | 0.000000898 | 0.000000863 | 0.000000932 |  0.00000052 |
K_{2} value.. |       0.235 |      0.2175 |       0.226 |      0.0204 |
--------------+-------------+-------------+-------------+---

----------+

The above values for various gums and dextrins were obtained at a constant temperature of 15 deg.  C. and are compared with water at that temperature.  It is of the utmost importance that the temperature of the water surrounding the bulbs should be adjusted for each series of experiments to the temperature at which the absolute viscosity of the water was determined.  As far as we have ascertained, in gum solutions there is a steady diminution in viscosity with increase of temperature until a certain temperature is reached, beyond which increase of heat does not markedly influence the viscosity, and it is possible that above this “critical point,” as we may term it, the gum solutions once more begin to increase in viscosity.  The temperature at which the viscosity becomes stationary varies somewhat with different gums, but broadly speaking it lies between 60 deg.  C. and 90 deg.  C., no gums showing any marked decrease in viscosity between 80 deg.  C. and 90 deg.  C.