HEATING APPARATUS FOR POLARIMETERS 
167 
equally adapted for use with ice at 0°, while fo? temperatures 
between 0° and that of the room a cooling coil connected with 
the water supply may be introduced. 
When the bath is connected with the observation tube and 
the stirrer is driven at the rate of 500 to 600 r. p. m., the water 
circulates through the tube with an exceedingly high velocity. 
To judge of the force driving the water, it may be stated that 
when the tubes, D, E, are open and the stirrer is revolving at 
the above rate, the lifting power of the stirrer is sufficient to 
support a colump of water eight inches in height. The speed 
with which the water is driven under hydrostatic equilibrium is, 
therefore, obvious. Under these conditions it is possible to main- 
tain any desired temperature constant to ±0.01° — ±0.02° for 
any desired period of time. 
Owing to the fact that the observation tube is of necessity at 
some distance from the bath, its temperature will be slightly 
lower and the difference will be greater, the higher the tem- 
perature to which the bath is heated. If the liquid in the ob- 
servation tube must be at a definite temperature, the tempera- 
ture of the bath can be adjusted easily so as to produce the de- 
sired temperature and the temperature of the tube regulate a 
with the same degree of constancy. 
Physical Chemical Laboratory, 
The State Universty of Iowa. 
