76 



OSMOTIC PRESSURE OF AQUEOUS SOLUTIONS. 



water. For most purposes, lamps of 8 or 10 candle-power suffice. If 

 temperatures but little above that of the room are to be maintained, the 

 electrical appliances only are employed to heat and regulate the baths. 

 For low temperatures, a coil of block-tin pipe is placed in the space (E, 

 E, Figure 39), and through it there is made to circulate, under constant 

 pressure, a current of hydrant water, which has previously been cooled 

 with ice if necessary. 



Fig. 45. — Exterior view of larger bath for high temperatures. 



In Figure 39 the thermostat is shown within the compartment (A), 

 while in Figure 38 it is represented as being immersed in the water of 

 the bath. The latter has been found to be the better of the two pos- 

 sible positions for the instrument. The temperature of the water 

 about the thermostat may not be precisely that of the interior compart- 

 ment, and at other points it may vary slightly, but when the instrument 

 has once been set for a given interior temperature, it is quite capable of 

 maintaining it for any length of time to within 0.01°, which is a rather 

 better regulation than can be secured in baths of Type III. 



