74 Dru^hel and Hill — Estevs of Halogen Substituted Acids, 



this action is probably due to the presence of the halogen- 

 substituted acetic acid. 



The Thermostat. — The thermostat used is cylindrical in 

 form, about 30 inches deep and 38 inches in diameter. It is 

 built of tinned copper and covered with a half-inch layer of 

 felt. It is supported on a heavy iron plate with a twelve-inch 

 hole in the center. This plate rests on legs about eight inches 

 above the floor so that one or more burners may be placed 

 beneath. A coil of lead-pipe around the inner wall about half- 

 way up, conducting steam or cold water, aids in rapidly chang- 



CI9 



Thermo-regulator. 

 A and B, toluol ; C and D, mercury ; E, alcohol. 



ing the temperature. For instance, when it is necessary to 

 change from a temperature of 25° to one of 40° this pipe is 

 connected with a steam pipe and steam heat is utilized. On 

 the other hand, a slow stream of cold water enables one to work 

 at a temperature below that of the room. When working at 

 high temperatures the thermostat is covered with asbestos 

 board to prevent radiation of heat from the large surface. 



The thermo-regulator is of special pattern and allows the 

 temperature to be changed at will. This apparatus, shown in 

 the accompanying cut, consists of a vertical cylindrical bulb of 

 400^^"' capacity tilled with toluol. To the 'top of this bulb 



